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Sikazwe G, Yocgo REE, Landi P, Richardson DM, Hui C. Current and future scenarios of suitability and expansion of cassava brown streak disease, Bemisia tabaci species complex, and cassava planting in Africa. PeerJ 2024; 12:e17386. [PMID: 38832032 PMCID: PMC11146326 DOI: 10.7717/peerj.17386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Accepted: 04/23/2024] [Indexed: 06/05/2024] Open
Abstract
Cassava (Manihot esculenta) is among the most important staple crops globally, with an imperative role in supporting the Sustainable Development Goal of 'Zero hunger'. In sub-Saharan Africa, it is cultivated mainly by millions of subsistence farmers who depend directly on it for their socio-economic welfare. However, its yield in some regions has been threatened by several diseases, especially the cassava brown streak disease (CBSD). Changes in climatic conditions enhance the risk of the disease spreading to other planting regions. Here, we characterise the current and future distribution of cassava, CBSD and whitefly Bemisia tabaci species complex in Africa, using an ensemble of four species distribution models (SDMs): boosted regression trees, maximum entropy, generalised additive model, and multivariate adaptive regression splines, together with 28 environmental covariates. We collected 1,422 and 1,169 occurrence records for cassava and Bemisia tabaci species complex from the Global Biodiversity Information Facility and 750 CBSD occurrence records from published literature and systematic surveys in East Africa. Our results identified isothermality as having the highest contribution to the current distribution of cassava, while elevation was the top predictor of the current distribution of Bemisia tabaci species complex. Cassava harvested area and precipitation of the driest month contributed the most to explain the current distribution of CBSD outbreaks. The geographic distributions of these target species are also expected to shift under climate projection scenarios for two mid-century periods (2041-2060 and 2061-2080). Our results indicate that major cassava producers, like Cameron, Ivory Coast, Ghana, and Nigeria, are at greater risk of invasion of CBSD. These results highlight the need for firmer agricultural management and climate-change mitigation actions in Africa to combat new outbreaks and to contain the spread of CBSD.
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Affiliation(s)
- Geofrey Sikazwe
- African Institute for Mathematical Sciences, Kigali, Rwanda
- Department of Mathematical Sciences, University of Stellenbosch, Stellenbosch, South Africa
- Mkwawa University College of Education, Iringa, Tanzania
| | - Rosita Endah epse Yocgo
- African Institute for Mathematical Sciences, Kigali, Rwanda
- Institute for Plant Biotechnology, Stellenbosch University, Stellenbosch, South Africa
| | - Pietro Landi
- Department of Mathematical Sciences, University of Stellenbosch, Stellenbosch, South Africa
- National Institute for Theoretical and Computational Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - David M. Richardson
- Institute of Botany, Czech Academy of Sciences, Průhonice, Czech Republic
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa
| | - Cang Hui
- Department of Mathematical Sciences, University of Stellenbosch, Stellenbosch, South Africa
- National Institute for Theoretical and Computational Sciences, Stellenbosch University, Stellenbosch, South Africa
- Mathematical Bioscience Unit, African Institute for Mathematical Sciences, Cape Town, South Africa
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2
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Sam W, Morris OS, Tom O, Patrick O, Colvin J, Abu OC. Resistance to Cassava Whitefly ( Bemisia tabaci) among Eastern and Southern African Elite Cassava Genotypes. INSECTS 2024; 15:258. [PMID: 38667388 PMCID: PMC11050530 DOI: 10.3390/insects15040258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Revised: 03/21/2024] [Accepted: 03/28/2024] [Indexed: 04/28/2024]
Abstract
Cassava whitefly, Bemisia tabaci, directly damages cassava leaves by feeding on phloem, causing chlorosis and abscission, leading to a yield loss of up to 50%. The pest also causes indirect damage through sooty mold formation. Most Ugandan cassava varieties resist cassava mosaic disease (CMD) and tolerate cassava brown streak disease (CBSD), but little is known about their response to whitefly infestation. The main objective of this study was to identify cassava genotypes with putative resistance to whitefly in Uganda. This was conducted on 24 improved cassava varieties in three agro-ecological zones during the second rains of 2016. Monthly data were taken for adult and nymph counts, whitefly and sooty mold damage, and CMD and CBSD severities from 2 to 9 months after planting (MAPs). The results show that the whitefly population is highly significantly (p < 0.000) amongst varieties across the three agro-ecological zones. Mkumba consistently supported the low adult numbers and nymphs. The findings demonstrate the potential of the improved cassava varieties as sources of whitefly resistance for sustainable management.
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Affiliation(s)
- Wamani Sam
- National Crops Resources Research Institute, Kampala P.O. Box 7084, Uganda; (O.S.M.); (O.T.); (O.P.); (O.C.A.)
| | - Opio Samuel Morris
- National Crops Resources Research Institute, Kampala P.O. Box 7084, Uganda; (O.S.M.); (O.T.); (O.P.); (O.C.A.)
| | - Omara Tom
- National Crops Resources Research Institute, Kampala P.O. Box 7084, Uganda; (O.S.M.); (O.T.); (O.P.); (O.C.A.)
| | - Ocitti Patrick
- National Crops Resources Research Institute, Kampala P.O. Box 7084, Uganda; (O.S.M.); (O.T.); (O.P.); (O.C.A.)
| | - John Colvin
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, Gillingham ME4 4TB, UK;
| | - Omongo Christopher Abu
- National Crops Resources Research Institute, Kampala P.O. Box 7084, Uganda; (O.S.M.); (O.T.); (O.P.); (O.C.A.)
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El Hamss H, Maruthi MN, Omongo CA, Wang HL, van Brunschot S, Colvin J, Delatte H. Microbiome diversity and composition in Bemisia tabaci SSA1-SG1 whitefly are influenced by their host's life stage. Microbiol Res 2024; 278:127538. [PMID: 37952351 DOI: 10.1016/j.micres.2023.127538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 10/19/2023] [Accepted: 10/29/2023] [Indexed: 11/14/2023]
Abstract
Within the Bemisia tabaci group of cryptic whitefly species, many are damaging agricultural pests and plant-virus vectors, conferring upon this group the status of one of the world's top 100 most invasive and destructive species, affecting farmers' income and threatening their livelihoods. Studies on the microbiome of whitefly life stages are scarce, although their composition and diversity greatly influence whitefly fitness and development. We used high-throughput sequencing to understand microbiome diversity in different developmental stages of the B. tabaci sub-Saharan Africa 1 (SSA1-SG1) species of the whitefly from Uganda. Endosymbionts (Portiera, Arsenophonus, Wolbachia, and Hemipteriphilus were detected but excluded from further statistical analysis as they were not influenced by life stage using Permutational Multivariate Analysis of Variance Using Distance Matrices (ADONIS, p = 0.925 and Bray, p = 0.903). Our results showed significant differences in the meta microbiome composition in different life stages of SSA1-SG1. The diversity was significantly higher in eggs (Shannon, p = 0.024; Simpson, p = 0.047) than that in nymphs and pupae, while the number of microbial species observed by the amplicon sequence variant (ASV) was not significant (n(ASV), p = 0.094). At the phylum and genus levels, the dominant constituents in the microbiome changed significantly during various developmental stages, with Halomonas being present in eggs, whereas Bacillus and Caldalkalibacillus were consistently found across all life stages. These findings provide the first description of differing meta microbiome diversity in the life stage of whiteflies, suggesting their putative role in whitefly development.
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Affiliation(s)
- Hajar El Hamss
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, United Kingdom.
| | - M N Maruthi
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, United Kingdom.
| | - Christopher A Omongo
- Root Crops Programme, National Crops Resource Research Institute (RCP-NaCRRI), Kampala, Uganda
| | - Hua-Ling Wang
- College of Forestry, Hebei Agricultural University, Hebei, China
| | - Sharon van Brunschot
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, United Kingdom; School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - John Colvin
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, United Kingdom
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Nye DG, Irigoyen ML, Perez-Fons L, Bohorquez-Chaux A, Hur M, Medina-Yerena D, Lopez-Lavalle LAB, Fraser PD, Walling LL. Integrative transcriptomics reveals association of abscisic acid and lignin pathways with cassava whitefly resistance. BMC PLANT BIOLOGY 2023; 23:657. [PMID: 38124051 PMCID: PMC10731783 DOI: 10.1186/s12870-023-04607-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 11/14/2023] [Indexed: 12/23/2023]
Abstract
BACKGROUND Whiteflies are a global threat to crop yields, including the African subsistence crop cassava (Manihot esculenta). Outbreaks of superabundant whitefly populations throughout Eastern and Central Africa in recent years have dramatically increased the pressures of whitefly feeding and virus transmission on cassava. Whitefly-transmitted viral diseases threaten the food security of hundreds of millions of African farmers, highlighting the need for developing and deploying whitefly-resistant cassava. However, plant resistance to whiteflies remains largely poorly characterized at the genetic and molecular levels. Knowledge of cassava-defense programs also remains incomplete, limiting characterization of whitefly-resistance mechanisms. To better understand the genetic basis of whitefly resistance in cassava, we define the defense hormone- and Aleurotrachelus socialis (whitefly)-responsive transcriptome of whitefly-susceptible (COL2246) and whitefly-resistant (ECU72) cassava using RNA-seq. For broader comparison, hormone-responsive transcriptomes of Arabidopsis thaliana were also generated. RESULTS Whitefly infestation, salicylic acid (SA), jasmonic acid (JA), ethylene (ET), and abscisic acid (ABA) transcriptome responses of ECU72 and COL2246 were defined and analyzed. Strikingly, SA responses were largely reciprocal between the two cassava genotypes and we suggest candidate regulators. While susceptibility was associated with SA in COL2246, resistance to whitefly in ECU72 was associated with ABA, with SA-ABA antagonism observed. This was evidenced by expression of genes within the SA and ABA pathways and hormone levels during A. socialis infestation. Gene-enrichment analyses of whitefly- and hormone-responsive genes suggest the importance of fast-acting cell wall defenses (e.g., elicitor recognition, lignin biosynthesis) during early infestation stages in whitefly-resistant ECU72. A surge of ineffective immune and SA responses characterized the whitefly-susceptible COL2246's response to late-stage nymphs. Lastly, in comparison with the model plant Arabidopsis, cassava's hormone-responsive genes showed striking divergence in expression. CONCLUSIONS This study provides the first characterization of cassava's global transcriptome responses to whitefly infestation and defense hormone treatment. Our analyses of ECU72 and COL2246 uncovered possible whitefly resistance/susceptibility mechanisms in cassava. Comparative analysis of cassava and Arabidopsis demonstrated that defense programs in Arabidopsis may not always mirror those in crop species. More broadly, our hormone-responsive transcriptomes will also provide a baseline for the cassava community to better understand global responses to other yield-limiting pests/pathogens.
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Affiliation(s)
- Danielle G Nye
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Maria L Irigoyen
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Laura Perez-Fons
- Department of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Adriana Bohorquez-Chaux
- Alliance Bioversity International and International Center for Tropical Agriculture (CIAT), Cali, Colombia
| | - Manhoi Hur
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
- Institute of Integrative Genome Biology, University of California, Riverside, CA, 92521, USA
| | - Diana Medina-Yerena
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA
| | - Luis Augusto Becerra Lopez-Lavalle
- Alliance Bioversity International and International Center for Tropical Agriculture (CIAT), Cali, Colombia
- Present Address: International Center of Biosaline Agriculture, Dubai, United Arab Emirates
| | - Paul D Fraser
- Department of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Linda L Walling
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92521, USA.
- Institute of Integrative Genome Biology, University of California, Riverside, CA, 92521, USA.
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Malichan S, Vannatim N, Chaowongdee S, Pongpamorn P, Paemanee A, Siriwan W. Comparative analysis of salicylic acid levels and gene expression in resistant, tolerant, and susceptible cassava varieties following whitefly-mediated SLCMV infection. Sci Rep 2023; 13:13610. [PMID: 37604906 PMCID: PMC10442324 DOI: 10.1038/s41598-023-40874-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 08/17/2023] [Indexed: 08/23/2023] Open
Abstract
Sri Lankan cassava mosaic virus (SLCMV), the primary pathogen responsible for cassava mosaic disease in cassava plantations, is transmitted via infected cutting stems and the whitefly vector, Bemisia tabaci. To obtain better insights into the defense mechanism of cassava against SLCMV, whiteflies were used to induce SLCMV infection for activating the salicylic acid (SA) signaling pathway, which triggers the innate immune system. The study aimed to investigate the specific interactions between viruliferous whiteflies and SA accumulation in resistant (C33), tolerant (Kasetsart 50; KU50), and susceptible (Rayong 11) cassava cultivars by infecting with SLCMV. Leaf samples were collected at various time points, from 1 to 7 days after inoculation (dai). The SA levels were quantified by gas chromatography-mass spectrometry and validated by quantitative reverse transcription polymerase chain reaction. The SA levels increased in KU50 and C33 plants at 2 and 3 dai, respectively, but remained undetected in Rayong11 plants. The expression of PR-9e, PR-7f5, SPS1, SYP121, Hsf8, and HSP90 increased in infected C33 plants at 4 dai, whereas that of KU50 plants decreased immediately at 2 dai, and that of Rayong11 plants increased at 1 dai but gradually decreased thereafter. These findings strongly indicate that SA plays a crucial role in regulating antiviral defense mechanisms, especially in SLCMV-resistant plants. Altogether, the findings provide valuable insights into the mechanisms underlying the activation of SA-mediated anti-SLCMV defense pathways, and the resistance, tolerance, and susceptibility of cassava, which can aid future breeding programs aimed at enhancing SLCMV resistance.
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Affiliation(s)
- Srihunsa Malichan
- Department of Plant Pathology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Nattachai Vannatim
- Department of Plant Pathology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand
| | - Somruthai Chaowongdee
- Center for Agricultural Biotechnology, Kasetsart University, Kamphaengsaen Campus, Nakhon Pathom, 73140, Thailand
- Center of Excellence on Agricultural Biotechnology (AG-BIO/MHESI), Bangkok, 10900, Thailand
| | - Pornkanok Pongpamorn
- National Omics Center, National Science and Technology Development Agency (NSTDA), Pathum Thani, 12120, Thailand
| | - Atchara Paemanee
- National Omics Center, National Science and Technology Development Agency (NSTDA), Pathum Thani, 12120, Thailand
| | - Wanwisa Siriwan
- Department of Plant Pathology, Faculty of Agriculture, Kasetsart University, Bangkok, 10900, Thailand.
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6
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Mbuta DM, Khamis FM, Sokame BM, Ng’ong’a F, Akutse KS. Household perception and infestation dynamics of bedbugs among residential communities and its potential distribution in Africa. Sci Rep 2022; 12:19900. [PMID: 36400831 PMCID: PMC9674637 DOI: 10.1038/s41598-022-24339-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 11/14/2022] [Indexed: 11/19/2022] Open
Abstract
Bedbugs have experienced an extraordinary upsurge in the recent past across the world. This cross-sectional study aimed to explore the community perception of the pest outbreaks, the population dynamics, and dispersal patterns under different habitat systems. A survey was conducted within communities in nine counties in Kenya, where geographical coordinates of the sites of bedbug presence were recorded and maximum entropy distribution modelling (MaxEnt) was used to map and predict the potentially suitable habitat, while system thinking and system dynamics approach with Vensim PLE 8.0.9 software was applied to implement bedbug infestation dynamics. Our results indicated that majority of the respondents had ample knowledge on bedbugs and were concerned about the physico-psychologic and socio-economic health effects. Spatial distribution analysis showed regions in Kenya with optimal to suitable for bedbug occurrence in the whole country, and similar results were found at continental level across Africa. Furthermore, infestation dynamics results showed a rapid mobility of bedbug from one house to another. In terms of management strategies, the models showed that the combination of chemical with other control methods was considerably much more effective compared to the use of chemical approach only, appointing integrated pest management strategy as a better intervention approach in controlling the pest.
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Affiliation(s)
- Dennis M. Mbuta
- grid.419326.b0000 0004 1794 5158International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya ,grid.411943.a0000 0000 9146 7108Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
| | - Fathiya M. Khamis
- grid.419326.b0000 0004 1794 5158International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya
| | - Bonoukpoè M. Sokame
- grid.419326.b0000 0004 1794 5158International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya
| | - Florence Ng’ong’a
- grid.411943.a0000 0000 9146 7108Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
| | - Komivi S. Akutse
- grid.419326.b0000 0004 1794 5158International Centre of Insect Physiology and Ecology, P.O. Box 30772-00100, Nairobi, Kenya
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Leiva AM, Chittarath K, Lopez-Alvarez D, Vongphachanh P, Gomez MI, Sengsay S, Wang XW, Rodriguez R, Newby J, Cuellar WJ. Mitochondrial Genetic Diversity of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava in Lao PDR. INSECTS 2022; 13:861. [PMID: 36292809 PMCID: PMC9604212 DOI: 10.3390/insects13100861] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 09/14/2022] [Accepted: 09/15/2022] [Indexed: 06/16/2023]
Abstract
Cassava Mosaic Disease (CMD) caused by Sri Lankan cassava mosaic virus (SLCMV), has rapidly spread in Southeast Asia (SEA) since 2016. Recently it has been documented in Lao PDR. Previous reports have identified whitefly species of B. tabaci as potential vectors of CMD in SEA, but their occurrence and distribution in cassava fields is not well known. We conducted a countrywide survey in Lao PDR for adult whiteflies in cassava fields, and determined the abundance and genetic diversity of the B. tabaci species complex using mitochondrial cytochrome oxidase I (mtCOI) sequencing. In order to expedite the process, PCR amplifications were performed directly on whitefly adults without DNA extraction, and mtCOI sequences obtained using nanopore portable-sequencing technology. Low whitefly abundances and two cryptic species of the B. tabaci complex, Asia II 1 and Asia II 6, were identified. This is the first work on abundance and genetic identification of whiteflies associated with cassava in Lao PDR. This study indicates currently only a secondary role for Asia II in spreading CMD or as a pest. Routine monitoring and transmission studies on Asia II 6 should be carried out to establish its potential role as a vector of SLCMV in this region.
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Affiliation(s)
- Ana M. Leiva
- Cassava Program, Crops for Nutrition and Health, International Center for Tropical Agriculture (CIAT), The Americas Hub, Km 17 Recta Cali-Palmira, Cali 763537, Colombia
| | - Khonesavanh Chittarath
- Plant Protection Center (PPC), Department of Agriculture, Ministry of Agriculture and Forestry, Vientiane P.O. Box 811, Laos
| | - Diana Lopez-Alvarez
- Department of Biological Sciences, Universidad Nacional de Colombia UNAL-Palmira, Palmira 763533, Colombia
| | - Pinkham Vongphachanh
- Plant Protection Center (PPC), Department of Agriculture, Ministry of Agriculture and Forestry, Vientiane P.O. Box 811, Laos
| | - Maria Isabel Gomez
- Cassava Program, Crops for Nutrition and Health, International Center for Tropical Agriculture (CIAT), The Americas Hub, Km 17 Recta Cali-Palmira, Cali 763537, Colombia
| | - Somkhit Sengsay
- Plant Protection Center (PPC), Department of Agriculture, Ministry of Agriculture and Forestry, Vientiane P.O. Box 811, Laos
| | - Xiao-Wei Wang
- Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China
| | - Rafael Rodriguez
- Cassava Program, Crops for Nutrition and Health, International Center for Tropical Agriculture (CIAT), The Americas Hub, Km 17 Recta Cali-Palmira, Cali 763537, Colombia
| | - Jonathan Newby
- Cassava Program Asia Office, Crops for Nutrition and Health, International Center for Tropical Agriculture (CIAT), Laos Country Office, Vientiane P.O. Box 783, Laos
| | - Wilmer J. Cuellar
- Cassava Program, Crops for Nutrition and Health, International Center for Tropical Agriculture (CIAT), The Americas Hub, Km 17 Recta Cali-Palmira, Cali 763537, Colombia
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Doungous O, Masky B, Levai DL, Bahoya JA, Minyaka E, Mavoungou JF, Mutuku JM, Pita JS. Cassava mosaic disease and its whitefly vector in Cameroon: Incidence, severity and whitefly numbers from field surveys. CROP PROTECTION (GUILDFORD, SURREY) 2022; 158:106017. [PMID: 35923211 PMCID: PMC9168542 DOI: 10.1016/j.cropro.2022.106017] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 06/13/2023]
Abstract
Cassava plays a key role in the food security and economy of Cameroon, but its production is constrained by cassava mosaic disease (CMD). However, comprehensive surveys of CMD in Cameroon have been lacking. This study aimed at evaluating the current status of CMD and its whitefly vector. Field surveys were conducted in 2020 using a sampling, diagnostics and data storage protocol that has been harmonized across 10 West and Central African countries for ease of comparison. Thirty plants per field were assessed for CMD severity, whitefly abundance and source of infection. Surveys were conducted in 343 fields and confirmed the presence of CMD in all 10 regions of Cameroon. Among the 10,057 assessed plants, 33.07% were deemed healthy (asymptomatic). At the field level, only 6.7% fields were found to be healthy. The mean CMD incidence across the country was 66.93%, and the mean severity score was 2.28. The main mode of infection was likely through contaminated cuttings. The mean whitefly count per plant was 5.78. This study is the first countrywide survey of CMD in Cameroon and provides insights that can be useful for improving the country's CMD intervention and management strategies.
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Affiliation(s)
- Oumar Doungous
- The Central and West African Virus Epidemiology (WAVE), Biotechnology Laboratory, Ekona Regional Research Centre, Institute of Agricultural Research for Development, PMB 25, Buea, Cameroon
| | - Boutou Masky
- The Central and West African Virus Epidemiology (WAVE), Biotechnology Laboratory, Ekona Regional Research Centre, Institute of Agricultural Research for Development, PMB 25, Buea, Cameroon
| | - Dopgima L. Levai
- The Central and West African Virus Epidemiology (WAVE), Biotechnology Laboratory, Ekona Regional Research Centre, Institute of Agricultural Research for Development, PMB 25, Buea, Cameroon
| | - Joseph A.L. Bahoya
- The Central and West African Virus Epidemiology (WAVE), Biotechnology Laboratory, Ekona Regional Research Centre, Institute of Agricultural Research for Development, PMB 25, Buea, Cameroon
| | - Emile Minyaka
- Institut Universitaire de Technologie/Faculté des Sciences, Université de Douala, BP 24157, Douala, Cameroon
| | - Jacques F. Mavoungou
- Institut de Recherches Agronomiques et Forestières (IRAF), The Central and West African Virus Epidemiology (WAVE), Libreville, Gabon
| | - J. Musembi Mutuku
- The Central and West African Virus Epidemiology (WAVE), Pôle Scientifique et d'Innovation de Bingerville, Université Félix Houphouët-Boigny, BP V34, Abidjan 01, Republic of Côte d'Ivoire
| | - Justin S. Pita
- The Central and West African Virus Epidemiology (WAVE), Pôle Scientifique et d'Innovation de Bingerville, Université Félix Houphouët-Boigny, BP V34, Abidjan 01, Republic of Côte d'Ivoire
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9
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Donnelly R, Gilligan CA. The role of pathogen-mediated insect superabundance in the East African emergence of a plant virus. THE JOURNAL OF ECOLOGY 2022; 110:1113-1124. [PMID: 35910423 PMCID: PMC9310957 DOI: 10.1111/1365-2745.13854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 01/22/2022] [Indexed: 06/15/2023]
Abstract
One of the major crops for food security is cassava. Superabundant Bemisia tabaci whitefly, comprising unusually high landscape populations of the insect, have been implicated in cassava virus emergence. Studies have been unable to select from several hypotheses, however, as to the dynamic drivers of superabundant whitefly associated with the emergence in East Africa of severe cassava mosaic disease. One possibility is that pathogenic modification of infected plants can itself increase the growth of insect vector colonies on infected plants.Through the modelling of population processes at the landscape scale we introduce a framework for analysing patterns in the association of disease and insect waves.Our analyses demonstrate the role of pathogen-mediated insect superabundance in a plant disease invasion. Synthesis. An elevated abundance of insects at the landscape scale is frequently implicated in invasions of the plant pathogens that they carry. We advance ecological understanding of plant disease invasions by showing how landscape data can be used to investigate the causes of insect vector superabundance.
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Affiliation(s)
- Ruairí Donnelly
- Department of Plant SciencesUniversity of CambridgeCambridgeUK
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10
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Sicat JPA, Visendi P, Sewe SO, Bouvaine S, Seal SE. Characterization of transposable elements within the Bemisia tabaci species complex. Mob DNA 2022; 13:12. [PMID: 35440097 PMCID: PMC9017028 DOI: 10.1186/s13100-022-00270-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Accepted: 03/30/2022] [Indexed: 12/24/2022] Open
Abstract
Background Whiteflies are agricultural pests that cause negative impacts globally to crop yields resulting at times in severe economic losses and food insecurity. The Bemisia tabaci whitefly species complex is the most damaging in terms of its broad crop host range and its ability to serve as vector for over 400 plant viruses. Genomes of whiteflies belonging to this species complex have provided valuable genomic data; however, transposable elements (TEs) within these genomes remain unexplored. This study provides the first accurate characterization of TE content within the B. tabaci species complex. Results This study identified that an average of 40.61% of the genomes of three whitefly species (MEAM1, MEDQ, and SSA-ECA) consists of TEs. The majority of the TEs identified were DNA transposons (22.85% average) while SINEs (0.14% average) were the least represented. This study also compared the TE content of the three whitefly genomes with three other hemipteran genomes and found significantly more DNA transposons and less LINEs in the whitefly genomes. A total of 63 TE superfamilies were identified to be present across the three whitefly species (39 DNA transposons, six LTR, 16 LINE, and two SINE). The sequences of the identified TEs were clustered which generated 5766 TE clusters. A total of 2707 clusters were identified as uniquely found within the whitefly genomes while none of the generated clusters were from both whitefly and non-whitefly TE sequences. This study is the first to characterize TEs found within different B. tabaci species and has created a standardized annotation workflow that could be used to analyze future whitefly genomes. Conclusion This study is the first to characterize the landscape of TEs within the B. tabaci whitefly species complex. The characterization of these elements within the three whitefly genomes shows that TEs occupy significant portions of B. tabaci genomes, with DNA transposons representing the vast majority. This study also identified TE superfamilies and clusters of TE sequences of potential interest, providing essential information, and a framework for future TE studies within this species complex. Supplementary Information The online version contains supplementary material available at 10.1186/s13100-022-00270-6.
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Affiliation(s)
- Juan Paolo A Sicat
- Natural Resources Institute, University of Greenwich, Central Avenue, Gillingham, Chatham, ME4 4TB, UK.
| | - Paul Visendi
- Centre for Agriculture and the Bioeconomy, Queensland University of Technology, Brisbane, QLD, 4000, Australia
| | - Steven O Sewe
- Natural Resources Institute, University of Greenwich, Central Avenue, Gillingham, Chatham, ME4 4TB, UK
| | - Sophie Bouvaine
- Natural Resources Institute, University of Greenwich, Central Avenue, Gillingham, Chatham, ME4 4TB, UK
| | - Susan E Seal
- Natural Resources Institute, University of Greenwich, Central Avenue, Gillingham, Chatham, ME4 4TB, UK
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11
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Nakatumba-Nabende J, Tusubira JF, Babirye C, Nsumba S, Abu CO. A dataset of cassava whitefly count images. Data Brief 2022; 41:107911. [PMID: 35198687 PMCID: PMC8845108 DOI: 10.1016/j.dib.2022.107911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/25/2022] [Accepted: 02/01/2022] [Indexed: 11/28/2022] Open
Abstract
Whiteflies are insect vectors that affect a variety of plants such as tomatoes, cabbages, sweet potatoes, eggplants, and cassava. In Uganda, whiteflies are a major contributor to the spread of Cassava Brown Streak Disease (CBSD). By suckling on infected cassava plants, whiteflies can potentially transfer the Cassava Brown Streak Virus that causes CBSD to uninfected clean plants nearby when they migrate. When they attack the cassava plants in large numbers, whiteflies can also cause significant physical damage through suckling. This eventually can lead to leaf loss or plant death. Whiteflies also excrete “honeydew”, which harbors a fungus known as “sooty mold” that covers the leaves, limiting access to sunlight which in turn affects plant food production. As part of their work, the cassava breeders often conduct studies to assess the population of whiteflies in cassava fields through a manual process of visual inspection which can be arduous and time-consuming. This paper presents a cassava whitefly dataset that has been curated to enable researchers to build solutions for the automation of the count and detection of whiteflies. The dataset contains 3,000 images captured in a whitefly trial site in Uganda. It depicts different variations of whitefly infestation from low to high infestation. This data has already been used to provide a proof-of-concept solution for whitefly counting based on Machine Learning approaches.
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12
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Modelling the dynamics of Cassava Mosaic Disease with non-cassava host plants. INFORMATICS IN MEDICINE UNLOCKED 2022. [DOI: 10.1016/j.imu.2022.101086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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13
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Challenges and opportunities for plant viruses under a climate change scenario. Adv Virus Res 2022. [DOI: 10.1016/bs.aivir.2022.08.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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14
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Tay WT, Court LN, Macfadyen S, Jacomb F, Vyskočilová S, Colvin J, De Barro PJ. A high-throughput amplicon sequencing approach for population-wide species diversity and composition survey. Mol Ecol Resour 2021; 22:1706-1724. [PMID: 34918473 DOI: 10.1111/1755-0998.13576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 11/16/2021] [Accepted: 12/06/2021] [Indexed: 11/30/2022]
Abstract
Management of agricultural pests requires an understanding of pest species diversity, their interactions with beneficial insects and spatial-temporal patterns of pest abundance. Invasive and agriculturally important insect pests can build up very high populations, especially in cropping landscapes. Traditionally, sampling effort for species identification involves small sample sizes and is labour intensive. Here, we describe a multi-primer high throughput sequencing (HTS) metabarcoding method and associated analytical workflow for a rapid, intensive, high-volume survey of pest species compositions. We demonstrate our method using the taxonomically challenging Bemisia pest cryptic species complex as examples. The whiteflies Bemisia including the 'tabaci' species are agriculturally important capable of vectoring diverse plant viruses that cause diseases and crop losses. Our multi-primer metabarcoding HTS amplicon approach simultaneously process high volumes of whitefly individuals, with efficiency to detect rare (i.e., 1%) test-species, while our improved whitefly primers for metabarcoding also detected beneficial hymenopteran parasitoid species from whitefly nymphs. Field-testing our redesigned Bemisia metabarcoding primer sets across the Tanzania, Uganda and Malawi cassava cultivation landscapes, we identified the sub-Saharan Africa 1 Bemisia putative species as the dominant pest species, with other cryptic Bemisia species being detected at various abundances. We also provide evidence that Bemisia species compositions can be affected by host crops and sampling techniques that target either nymphs or adults. Our multi-primer HTS metabarcoding method incorporated two over-lapping amplicons of 472bp and 518bp that spanned the entire 657bp 3' barcoding region for Bemisia, and is particularly suitable to molecular diagnostic surveys of this highly cryptic insect pest species complex that also typically exhibited high population densities in heavy crop infestation episodes. Our approach can be adopted to understand species biodiversity across landscapes, with broad implications for improving trans-boundary biosecurity preparedness, thus contributing to molecular ecological knowledge and the development of control strategies for high-density, cryptic, pest-species complexes.
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Affiliation(s)
- W T Tay
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT, 2601, Australia
| | - L N Court
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT, 2601, Australia
| | - S Macfadyen
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT, 2601, Australia
| | - F Jacomb
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT, 2601, Australia
| | - S Vyskočilová
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT, 2601, Australia.,Natural Resources Institute, University of Greenwich, Central Avenue, Chatham, Maritime Kent, ME4 4TB, United Kingdom
| | - J Colvin
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham, Maritime Kent, ME4 4TB, United Kingdom
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15
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Mugerwa H, Wang H, Sseruwagi P, Seal S, Colvin J. Whole-genome single nucleotide polymorphism and mating compatibility studies reveal the presence of distinct species in sub-Saharan Africa Bemisia tabaci whiteflies. INSECT SCIENCE 2021; 28:1553-1566. [PMID: 33146464 PMCID: PMC9292209 DOI: 10.1111/1744-7917.12881] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 10/06/2020] [Accepted: 10/26/2020] [Indexed: 05/21/2023]
Abstract
In sub-Saharan Africa cassava growing areas, two members of the Bemisia tabaci species complex termed sub-Saharan Africa 1 (SSA1) and SSA2 have been reported as the prevalent whiteflies associated with the spread of viruses that cause cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) pandemics. At the peak of CMD pandemic in the late 1990s, SSA2 was the prevalent whitefly, although its numbers have diminished over the last two decades with the resurgence of SSA1 whiteflies. Three SSA1 subgroups (SG1 to SG3) are the predominant whiteflies in East Africa and vary in distribution and biological properties. Mating compatibility between SSA1 subgroups and SSA2 whiteflies was reported as the possible driver for the resurgence of SSA1 whiteflies. In this study, a combination of both phylogenomic methods and reciprocal crossing experiments were applied to determine species status of SSA1 subgroups and SSA2 whitefly populations. Phylogenomic analyses conducted with 26 548 205 bp whole genome single nucleotide polymorphisms (SNPs) and the full mitogenomes clustered SSA1 subgroups together and separate from SSA2 species. Mating incompatibility between SSA1 subgroups and SSA2 further demonstrated their distinctiveness from each other. Phylogenomic analyses conducted with SNPs and mitogenomes also revealed different genetic relationships among SSA1 subgroups. The former clustered SSA1-SG1 and SSA1-SG2 together but separate from SSA1-SG3, while the latter clustered SSA1-SG2 and SSA1-SG3 together but separate from SSA1-SG1. Mating compatibility was observed between SSA1-SG1 and SSA1-SG2, while incompatibility occurred between SSA1-SG1 and SSA1-SG3, and SSA1-SG2 and SSA1-SG3. Mating results among SSA1 subgroups were coherent with phylogenomics results based on SNPs but not the full mitogenomes. Furthermore, this study revealed that the secondary endosymbiont-Wolbachia-did not mediate reproductive success in the crossing assays carried out. Overall, using genome wide SNPs together with reciprocal crossings assays, this study established accurate genetic relationships among cassava-colonizing populations, illustrating that SSA1 and SSA2 are distinct species while at least two species occur within SSA1 species.
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Affiliation(s)
- Habibu Mugerwa
- Natural Resources InstituteUniversity of GreenwichCentral AvenueChatham MaritimeKentUK
- Department of EntomologyUniversity of GeorgiaGriffinGeorgiaUSA
| | - Hua‐Ling Wang
- Natural Resources InstituteUniversity of GreenwichCentral AvenueChatham MaritimeKentUK
- Institute of Insect SciencesZhejiang UniversityHangzhouChina
| | - Peter Sseruwagi
- Biotechnology DepartmentMikocheni Agricultural Research InstituteDar es SalaamTanzania
| | - Susan Seal
- Natural Resources InstituteUniversity of GreenwichCentral AvenueChatham MaritimeKentUK
| | - John Colvin
- Natural Resources InstituteUniversity of GreenwichCentral AvenueChatham MaritimeKentUK
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16
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Soro M, Tiendrébéogo F, Pita JS, Traoré ET, Somé K, Tibiri EB, Néya JB, Mutuku JM, Simporé J, Koné D. Epidemiological assessment of cassava mosaic disease in Burkina Faso. PLANT PATHOLOGY 2021; 70:2207-2216. [PMID: 35873883 PMCID: PMC9291739 DOI: 10.1111/ppa.13459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 08/05/2021] [Indexed: 05/11/2023]
Abstract
Surveys were conducted in 2016 and 2017 across the main cassava-growing regions of Burkina Faso to assess the status of cassava mosaic disease (CMD) and to determine the virus strains causing the disease, using field observation and phylogenetic analysis. CMD incidence varied between regions and across years but was lowest in Hauts-Bassins (6.0%, 2016 and 5.4%, 2017) and highest in Centre-Sud (18.5%, 2016) and in Boucle du Mouhoun (51.7%, 2017). The lowest CMD severity was found in Est region (2.0) for both years and the highest in Sud-Ouest region (3.3, 2016) and Centre-Sud region (2.8, 2017). The CMD infection was primarily associated with contaminated cuttings in all regions except in Hauts-Bassins, where whitefly-borne infection was higher than cuttings-borne infection in 2016. PCR screening of 687 samples coupled with sequence analysis revealed the presence of African cassava mosaic-like (ACMV-like) viruses and East African cassava mosaic-like (EACMV-like) viruses as single infections at 79.5% and 1.1%, respectively. Co-infections of ACMV-like and EACMV-like viruses were detected in 19.4% of the tested samples. In addition, 86.7% of the samples positive for EACMV-like virus were found to be positive for East African cassava mosaic Cameroon virus (EACMCMV). Phylogenetic analysis revealed the segregation of cassava mosaic geminiviruses (CMGs) from Burkina Faso into three clades specific to ACMV, African cassava mosaic Burkina Faso virus (ACMBFV), and EACMCMV, confirming the presence of these viruses. The results of this study show that EACMCMV occurrence may be more prevalent in Burkina Faso than previously thought.
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Affiliation(s)
- Monique Soro
- Central and West African Virus Epidemiology (WAVE)Pôle scientifique et d’innovation de BingervilleUniversité Félix Houphouët‐Boigny (UFHB)BingervilleIvory Coast
- Laboratoire de Biotechnologie, Agriculture et Valorisation des Ressources BiologiquesUFR BiosciencesUniversité Félix Houphouët‐BoignyAbidjanIvory Coast
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
| | - Fidèle Tiendrébéogo
- Central and West African Virus Epidemiology (WAVE)Pôle scientifique et d’innovation de BingervilleUniversité Félix Houphouët‐Boigny (UFHB)BingervilleIvory Coast
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
| | - Justin S. Pita
- Central and West African Virus Epidemiology (WAVE)Pôle scientifique et d’innovation de BingervilleUniversité Félix Houphouët‐Boigny (UFHB)BingervilleIvory Coast
- Laboratoire de Biotechnologie, Agriculture et Valorisation des Ressources BiologiquesUFR BiosciencesUniversité Félix Houphouët‐BoignyAbidjanIvory Coast
| | - Edwig T. Traoré
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
- Laboratoire de Biologie Moléculaire et de Génétique (LABIOGENE)Université Joseph Ki‐ZerboOuagadougouBurkina Faso
| | - Koussao Somé
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
- Laboratoire de Génétique et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
| | - Ezechiel B. Tibiri
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
| | - James B. Néya
- Laboratoire de Virologie et de Biotechnologies VégétalesInstitut de l’Environnement et de Recherches Agricoles (INERA)OuagadougouBurkina Faso
- Laboratoire Mixte International Patho‐BiosIRD‐INERAOuagadougouBurkina Faso
| | - J. Musembi Mutuku
- Central and West African Virus Epidemiology (WAVE)Pôle scientifique et d’innovation de BingervilleUniversité Félix Houphouët‐Boigny (UFHB)BingervilleIvory Coast
| | - Jacques Simporé
- Laboratoire de Biologie Moléculaire et de Génétique (LABIOGENE)Université Joseph Ki‐ZerboOuagadougouBurkina Faso
| | - Daouda Koné
- Laboratoire de Biotechnologie, Agriculture et Valorisation des Ressources BiologiquesUFR BiosciencesUniversité Félix Houphouët‐BoignyAbidjanIvory Coast
- Centre d’Excellence Africain sur le Changement Climatique, la Biodiversité et l’Agriculture Durable (WASCAL/CEA‐CCBAD, Université Félix Houphouët‐Boigny)PSI‐Université Félix Houphouët‐BoignyAbidjanIvory Coast
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17
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Katono K, Macfadyen S, Omongo CA, Odong TL, Colvin J, Karungi J, Otim MH. Influence of Cassava Morphological Traits and Environmental Conditions on Field Populations of Bemisia tabaci. INSECTS 2021; 12:insects12070604. [PMID: 34357264 PMCID: PMC8306399 DOI: 10.3390/insects12070604] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/28/2021] [Accepted: 06/29/2021] [Indexed: 11/16/2022]
Abstract
High populations of species in the whitefly complex Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) were reported to cause severe damage to cassava in East and Central Africa. However, reasons for B. tabaci population increases are not well understood. We investigated the effect of cassava morphological traits, temperature, rainfall and relative humidity (RH) on the abundance of B. tabaci. Five cassava genotypes with varying levels of resistance to cassava mosaic disease, cassava brown streak disease, and B. tabaci infestation were planted in three Ugandan agro-ecological zones. The experiment was conducted in 2016 and 2017 in a randomized complete block design. Across all locations, the tallest genotype Alado alado supported the lowest number of B. tabaci adults. In areas with high B. tabaci prevalence, leaf area, leaf lobe width, and leaf lobe number exhibited significant positive effects (p < 0.001) on B. tabaci adult count. Positive effects of relative humidity and negative effects of temperature and rainfall on B. tabaci adult and nymph counts were observed in 2016 and 2017, resulting in low populations in Lira. Evidently, temperatures of 28-30 °C, rainfall of 30-150 mm and RH of 55-70%, and deployment of cassava genotypes of low plant height, large leaf area, and lobe width significantly enhanced B. tabaci population growth.
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Affiliation(s)
- Kasifa Katono
- Department of Agricultural Production, School of Agricultural Sciences, College of Agricultural and Environmental Sciences, Makerere University, P.O. Box 7062 Kampala, Uganda; (T.L.O.); (J.K.)
- National Crops Resources Research Institute, P.O. Box 7084 Kampala, Uganda; (C.A.O.); (M.H.O.)
- Correspondence: ; Tel.: +256-783-810023
| | | | - Christopher Abu Omongo
- National Crops Resources Research Institute, P.O. Box 7084 Kampala, Uganda; (C.A.O.); (M.H.O.)
| | - Thomas Lapaka Odong
- Department of Agricultural Production, School of Agricultural Sciences, College of Agricultural and Environmental Sciences, Makerere University, P.O. Box 7062 Kampala, Uganda; (T.L.O.); (J.K.)
| | - John Colvin
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK;
| | - Jeninah Karungi
- Department of Agricultural Production, School of Agricultural Sciences, College of Agricultural and Environmental Sciences, Makerere University, P.O. Box 7062 Kampala, Uganda; (T.L.O.); (J.K.)
| | - Michael Hilary Otim
- National Crops Resources Research Institute, P.O. Box 7084 Kampala, Uganda; (C.A.O.); (M.H.O.)
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18
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Elfekih S, Tay WT, Polaszek A, Gordon KHJ, Kunz D, Macfadyen S, Walsh TK, Vyskočilová S, Colvin J, De Barro PJ. On species delimitation, hybridization and population structure of cassava whitefly in Africa. Sci Rep 2021; 11:7923. [PMID: 33846476 PMCID: PMC8041820 DOI: 10.1038/s41598-021-87107-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 03/17/2021] [Indexed: 01/03/2023] Open
Abstract
The Bemisia cassava whitefly complex includes species that cause severe crop damage through vectoring cassava viruses in eastern Africa. Currently, this whitefly complex is divided into species and subgroups (SG) based on very limited molecular markers that do not allow clear definition of species and population structure. Based on 14,358 genome-wide SNPs from 62 Bemisia cassava whitefly individuals belonging to sub-Saharan African species (SSA1, SSA2 and SSA4), and using a well-curated mtCOI gene database, we show clear incongruities in previous taxonomic approaches underpinned by effects from pseudogenes. We show that the SSA4 species is nested within SSA2, and that populations of the SSA1 species comprise well-defined south-eastern (Madagascar, Tanzania) and north-western (Nigeria, Democratic Republic of Congo, Burundi) putative sub-species. Signatures of allopatric incipient speciation, and the presence of a 'hybrid zone' separating the two putative sub-species were also detected. These findings provide insights into the evolution and molecular ecology of a highly cryptic hemipteran insect complex in African, and allow the systematic use of genomic data to be incorporated in the development of management strategies for this cassava pest.
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Affiliation(s)
- S Elfekih
- Australian Centre for Disease Preparedness, CSIRO, Geelong, VIC, Australia
| | - W T Tay
- Black Mountain Laboratories, CSIRO, Canberra, ACT, Australia.
| | - A Polaszek
- Department of Life Sciences, Natural History Museum, London, UK
| | - K H J Gordon
- Black Mountain Laboratories, CSIRO, Canberra, ACT, Australia
| | - D Kunz
- The Gurdon Institute, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QN, UK
| | - S Macfadyen
- Black Mountain Laboratories, CSIRO, Canberra, ACT, Australia
| | - T K Walsh
- Black Mountain Laboratories, CSIRO, Canberra, ACT, Australia
| | - S Vyskočilová
- Natural Resources Institute, University of Greenwich, Kent, UK
| | - J Colvin
- Natural Resources Institute, University of Greenwich, Kent, UK
| | - P J De Barro
- CSIRO, Ecosciences Precinct, Brisbane, Australia
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Kalyebi A, Macfadyen S, Hulthen A, Ocitti P, Jacomb F, Tay WT, Colvin J, De Barro P. Within-Season Changes in Land-Use Impact Pest Abundance in Smallholder African Cassava Production Systems. INSECTS 2021; 12:269. [PMID: 33810012 PMCID: PMC8005198 DOI: 10.3390/insects12030269] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 12/30/2022]
Abstract
Cassava (Manihot esculenta Crantz), an important commercial and food security crop in East and Central Africa, continues to be adversely affected by the whitefly Bemisia tabaci. In Uganda, changes in smallholder farming landscapes due to crop rotations can impact pest populations but how these changes affect pest outbreak risk is unknown. We investigated how seasonal changes in land-use have affected B. tabaci population dynamics and its parasitoids. We used a large-scale field experiment to standardize the focal field in terms of cassava age and cultivar, then measured how Bemisia populations responded to surrounding land-use change. Bemisia tabaci Sub-Saharan Africa 1 (SSA1) was identified using molecular diagnostics as the most prevalent species and the same species was also found on surrounding soybean, groundnut, and sesame crops. We found that an increase in the area of cassava in the 3-7-month age range in the landscape resulted in an increase in the abundance of the B. tabaci SSA1 on cassava. There was a negative relationship between the extent of non-crop vegetation in the landscape and parasitism of nymphs suggesting that these parasitoids do not rely on resources in the non-crop patches. The highest abundance of B. tabaci SSA1 nymphs in cassava fields occurred at times when landscapes had large areas of weeds, low to moderate areas of maize, and low areas of banana. Our results can guide the development of land-use strategies that smallholder farmers can employ to manage these pests.
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Affiliation(s)
- Andrew Kalyebi
- National Crops Resources Research Institute, P.O. Box 7084, Kampala, Uganda;
- Mikocheni Agricultural Institute, Dares Salaam 6226, Tanzania
| | - Sarina Macfadyen
- CSIRO, Clunnies Ross Street, Acton 2601, Australia; (S.M.); (F.J.); (W.T.T.)
| | - Andrew Hulthen
- CSIRO, Ecosciences Preceinct, Dutton Park QLD, Brisbane 4001, Australia; (A.H.); (P.D.B.)
| | - Patrick Ocitti
- National Crops Resources Research Institute, P.O. Box 7084, Kampala, Uganda;
| | - Frances Jacomb
- CSIRO, Clunnies Ross Street, Acton 2601, Australia; (S.M.); (F.J.); (W.T.T.)
| | - Wee Tek Tay
- CSIRO, Clunnies Ross Street, Acton 2601, Australia; (S.M.); (F.J.); (W.T.T.)
| | - John Colvin
- NRI, University of Greenwich, Chatham, Maritime, Kent ME4 4TB, UK;
| | - Paul De Barro
- CSIRO, Ecosciences Preceinct, Dutton Park QLD, Brisbane 4001, Australia; (A.H.); (P.D.B.)
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20
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Mugerwa H, Sseruwagi P, Colvin J, Seal S. Is High Whitefly Abundance on Cassava in Sub-Saharan Africa Driven by Biological Traits of a Specific, Cryptic Bemisia tabaci Species? INSECTS 2021; 12:260. [PMID: 33804645 PMCID: PMC8003695 DOI: 10.3390/insects12030260] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 03/06/2021] [Accepted: 03/17/2021] [Indexed: 11/17/2022]
Abstract
In East Africa, the prevalent Bemisia tabaci whiteflies on the food security crop cassava are classified as sub-Saharan Africa (SSA) species. Economically damaging cassava whitefly populations were associated with the SSA2 species in the 1990s, but more recently, it has been to SSA1 species. To investigate whether biological traits (number of first instar nymphs, emerged adults, proportion of females in progeny and development time) of the cassava whitefly species are significant drivers of the observed field abundance, our study determined the development of SSA1 sub-group (SG) 1 (5 populations), SG2 (5 populations), SG3 (1 population) and SSA2 (1 population) on cassava and eggplant under laboratory conditions. SSA1-(SG1-SG2) and SSA2 populations' development traits were similar. Regardless of the host plant, SSA1-SG2 populations had the highest number of first instar nymphs (60.6 ± 3.4) and emerged adults (50.9 ± 3.6), followed by SSA1-SG1 (55.5 ± 3.2 and 44.6 ± 3.3), SSA2 (45.8 ± 5.7 and 32.6 ± 5.1) and the lowest were SSA1-SG3 (34.2 ± 6.1 and 32.0 ± 7.1) populations. SSA1-SG3 population had the shortest egg-adult emergence development time (26.7 days), followed by SSA1-SG1 (29.1 days), SSA1-SG2 (29.6 days) and SSA2 (32.2 days). Regardless of the whitefly population, development time was significantly shorter on eggplant (25.1 ± 0.9 days) than cassava (34.6 ± 1.0 days). These results support that SSA1-(SG1-SG2) and SSA2 B. tabaci can become highly abundant on cassava, with their species classification alone not correlating with observed abundance and prevalence.
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Affiliation(s)
- Habibu Mugerwa
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK;
- Department of Entomology, University of Georgia, 1109 Experiment Street, Griffin, GA 30223, USA
| | - Peter Sseruwagi
- Biotechnology Department, Mikocheni Agricultural Research Institute, P.O. Box 6226 Dar es Salaam, Tanzania;
| | - John Colvin
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK;
| | - Susan Seal
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK;
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Palanivel H, Shah S. Unlocking the inherent potential of plant genetic resources: food security and climate adaptation strategy in Fiji and the Pacific. ENVIRONMENT, DEVELOPMENT AND SUSTAINABILITY 2021; 23:14264-14323. [PMID: 33619427 PMCID: PMC7888530 DOI: 10.1007/s10668-021-01273-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
Pacific Island Countries (PICs) are the center of origin and diversity for several root, fruit and nut crops, which are indispensable for food security, rural livelihoods, and cultural identity of local communities. However, declining genetic diversity of traditional food crops and high vulnerability to climate change are major impediments for maintaining agricultural productivity. Limited initiatives to achieve food self-sufficiency and utilization of Plant Genetic Resources (PGR) for enhancing resilience of agro-ecosystems are other serious constraints. This review focuses on the visible and anticipated impacts of climate ge, on major food and tree crops in agriculture and agroforestry systems in the PICs. We argue that crop improvement through plant breeding is a viable strategy to enhance food security and climatic resilience in the region. The exploitation of adaptive traits: abiotic and biotic stress tolerance, yield and nutritional efficiency, is imperative in a world threatened by climatic extremes. However, the insular constraints of Fiji and other small PICs are major limitations for the utilization of PGR through high throughput techniques which are also cost prohibitive. Crop Improvement programs should instead focus on the identification, conservation, documentation and dissemination of information on unique landraces, community seed banks, introduction of new resistant genotypes, and sustaining and enhancing allelic diversity.
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Affiliation(s)
- Hemalatha Palanivel
- Department of Biotechnology, College of Biological and Chemical Engineering, Addis Ababa Science and Technology University, PO Box 16417, Addis Ababa, Ethiopia
| | - Shipra Shah
- Department of Forestry, College of Agriculture, Fisheries and Forestry, Koronivia Campus, Fiji National University, PO Box 1544, Nausori, Republic of Fiji
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Mugerwa H, Colvin J, Alicai T, Omongo CA, Kabaalu R, Visendi P, Sseruwagi P, Seal SE. Genetic diversity of whitefly ( Bemisia spp.) on crop and uncultivated plants in Uganda: implications for the control of this devastating pest species complex in Africa. JOURNAL OF PEST SCIENCE 2021; 94:1307-1330. [PMID: 34720787 PMCID: PMC8550740 DOI: 10.1007/s10340-021-01355-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/09/2021] [Accepted: 02/18/2021] [Indexed: 05/12/2023]
Abstract
UNLABELLED Over the past three decades, highly increased whitefly (Bemisia tabaci) populations have been observed on the staple food crop cassava in eastern Africa and associated with ensuing viral disease pandemics and food insecurity. Increased whitefly numbers have also been observed in other key agricultural crops and weeds. Factors behind the population surges on different crops and their interrelationships are unclear, although in cassava they have been associated with specific populations within the Bemisia tabaci species complex known to infest cassava crops in Africa. This study carried out an in-depth survey to understand the distribution of B. tabaci populations infesting crops and uncultivated plant hosts in Uganda, a centre of origin for this pest complex. Whitefly samples were collected from 59 identified plant species and 25 unidentified weeds in a countrywide survey. Identities of 870 individual adult whiteflies were determined through mitochondrial cytochrome oxidase 1 sequences (651 bp) in the 3' barcode region used for B. tabaci systematics. Sixteen B. tabaci and five related whitefly putative species were identified based on > 4.0% nucleotide divergence, of which three are proposed as novel B. tabaci putative species and four as novel closely related whitefly species. The most prevalent whiteflies were classified as B. tabaci MED-ASL (30.5% of samples), sub-Saharan Africa 1 (SSA1, 22.7%) and Bemisia Uganda1 (12.1%). These species were also indicated to be the most polyphagous occurring on 33, 40 and 25 identified plant species, respectively. Multiple (≥ 3) whitefly species occurred on specific crops (bean, eggplant, pumpkin and tomato) and weeds (Sida acuta and Ocimum gratissimum). These plants may have increased potential to act as reservoirs for mixed infections of whitefly-vectored viruses. Management of whitefly pest populations in eastern Africa will require an integration of approaches that consider their degree of polyphagy and a climate that enables the continuous presence of crop and uncultivated plant hosts. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1007/s10340-021-01355-6.
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Affiliation(s)
- Habibu Mugerwa
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB UK
- Department of Entomology, University of Georgia, 1109 Experiment Street, Griffin, GA 30223 USA
| | - John Colvin
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB UK
| | - Titus Alicai
- Root Crops Programme, National Crops Resources Research Institute, P. O. Box 7084, Kampala, Uganda
| | - Christopher A. Omongo
- Root Crops Programme, National Crops Resources Research Institute, P. O. Box 7084, Kampala, Uganda
| | - Richard Kabaalu
- Root Crops Programme, National Crops Resources Research Institute, P. O. Box 7084, Kampala, Uganda
| | - Paul Visendi
- Centre for Agriculture and Bioeconomy, Queensland University of Technology, Brisbane, 4001 Australia
| | - Peter Sseruwagi
- Biotechnology Department, Mikocheni Agricultural Research Institute, P.O. Box 6226, Dar es Salaam, Tanzania
| | - Susan E. Seal
- Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB UK
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Improving climate suitability for Bemisia tabaci in East Africa is correlated with increased prevalence of whiteflies and cassava diseases. Sci Rep 2020; 10:22049. [PMID: 33328547 PMCID: PMC7744558 DOI: 10.1038/s41598-020-79149-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 11/26/2020] [Indexed: 11/18/2022] Open
Abstract
Projected climate changes are thought to promote emerging infectious diseases, though to date, evidence linking climate changes and such diseases in plants has not been available. Cassava is perhaps the most important crop in Africa for smallholder farmers. Since the late 1990’s there have been reports from East and Central Africa of pandemics of begomoviruses in cassava linked to high abundances of whitefly species within the Bemisia tabaci complex. We used CLIMEX, a process-oriented climatic niche model, to explore if this pandemic was linked to recent historical climatic changes. The climatic niche model was corroborated with independent observed field abundance of B. tabaci in Uganda over a 13-year time-series, and with the probability of occurrence of B. tabaci over 2 years across the African study area. Throughout a 39-year climate time-series spanning the period during which the pandemics emerged, the modelled climatic conditions for B. tabaci improved significantly in the areas where the pandemics had been reported and were constant or decreased elsewhere. This is the first reported case where observed historical climate changes have been attributed to the increase in abundance of an insect pest, contributing to a crop disease pandemic.
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Li J, Aidlin Harari O, Doss A, Walling LL, Atkinson PW, Morin S, Tabashnik BE. Can CRISPR gene drive work in pest and beneficial haplodiploid species? Evol Appl 2020; 13:2392-2403. [PMID: 33005229 PMCID: PMC7513724 DOI: 10.1111/eva.13032] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 05/05/2020] [Accepted: 05/07/2020] [Indexed: 02/06/2023] Open
Abstract
Gene drives based on CRISPR/Cas9 have the potential to reduce the enormous harm inflicted by crop pests and insect vectors of human disease, as well as to bolster valued species. In contrast with extensive empirical and theoretical studies in diploid organisms, little is known about CRISPR gene drive in haplodiploids, despite their immense global impacts as pollinators, pests, natural enemies of pests, and invasive species in native habitats. Here, we analyze mathematical models demonstrating that, in principle, CRISPR homing gene drive can work in haplodiploids, as well as at sex-linked loci in diploids. However, relative to diploids, conditions favoring the spread of alleles deleterious to haplodiploid pests by CRISPR gene drive are narrower, the spread is slower, and resistance to the drive evolves faster. By contrast, the spread of alleles that impose little fitness cost or boost fitness was not greatly hindered in haplodiploids relative to diploids. Therefore, altering traits to minimize damage caused by harmful haplodiploids, such as interfering with transmission of plant pathogens, may be more likely to succeed than control efforts based on introducing traits that reduce pest fitness. Enhancing fitness of beneficial haplodiploids with CRISPR gene drive is also promising.
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Affiliation(s)
- Jun Li
- Department of StatisticsUniversity of CaliforniaRiversideCAUSA
| | | | | | - Linda L. Walling
- Department of Botany and Plant SciencesUniversity of CaliforniaRiversideCAUSA
| | | | - Shai Morin
- Department of EntomologyHebrew University of JerusalemRehovotIsrael
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Abstract
When increasing abundance of insect vectors is manifest across multiple fields of a crop at the landscape scale, the phenomenon is sometimes referred to as insect superabundance. The phenomenon may reflect environmental factors (i.e. environmentally mediated insect superabundance, EMiS), including climatic change. A number of pathogens, however, are also known to modify the quality of infected plants as a resource for their insect vectors. In this paper, we term increasing vector abundance when associated with pathogen modification of plants as pathogen-mediated insect superabundance (henceforth PMiS). We investigate PMiS using a new epidemiological framework. We formalize a definition of PMiS and indicate the epidemiological mechanism by which it is most likely to arise. This study is motivated by the occurrence of a particularly destructive cassava virus epidemic that has been associated with superabundant whitefly populations in sub-Saharan Africa. Our results have implications for how PMiS can be distinguished from EMiS in field data. Above all, they represent a timely foundation for further investigations into the association between insect superabundance and plant pathogens.
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Affiliation(s)
- Ruairí Donnelly
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, UK
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Host Plant Affects Symbiont Abundance in Bemisia tabaci (Hemiptera: Aleyrodidae). INSECTS 2020; 11:insects11080501. [PMID: 32759695 PMCID: PMC7469152 DOI: 10.3390/insects11080501] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 07/31/2020] [Accepted: 08/01/2020] [Indexed: 12/16/2022]
Abstract
Simple Summary The nutritional contributions of symbionts facilitate herbivores’ plant utilization, promoting insects infecting and spreading on host plants. In this study we investigated the effects of host plants on the symbionts of Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) from a nutritional aspect. We found that three host plant-adapted whitefly populations harbored the same symbiont taxa in different quantities. The amount of the primary symbiont Portiera decreased with increasing host-plant essential amino acid proportions in whitefly populations and even in those transferred to different host-plant species to meet the nutritional demands of whiteflies. However, the abundance of the secondary symbionts in whiteflies after host-plant-shifting for one generation showed little correlation with essential amino acid levels of host plants. It demonstrates that host-plant nitrogen nutrition—mainly, essential amino acids—influences the abundance of symbionts, especially Portiera, to meet whiteflies’ nutritional demands, and whiteflies manipulate their symbionts’ quantity governed by the host plant. The nutrient exchanges in symbioses involving multiple partners could provide new ideas for pest control. Abstract Symbionts contribute nutrients that allow insects to feed on plants. The whitefly Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a polyphagous pest that depends on symbionts to provide key nutrients that are deficient in the diet. Here, we established three whitefly populations on eggplants, cucumbers, and tomatoes and observed that they harbored the same symbiont taxa in different quantities. The amount of the primary symbiont, Portiera, decreased with increasing concentrations of host-plant essential amino acids (EAAs). Whitefly populations transferred to different plant species exhibited fluctuations in Portiera amounts in the first three or four generations; the amount of Portiera increased when whitefly populations were transferred to plant species with lower EAAs proportions. As for the secondary symbionts, the whitefly population of eggplants exhibited lower quantities of Hamiltonella and higher quantities of Rickettsia than the other two populations. The changes of both symbionts’ abundance in whitefly populations after host-plant-shifting for one generation showed little correlation with the EAAs’ proportions of host plants. These findings suggest that host-plant nitrogen nutrition, mainly in the form of EAAs, influences the abundance of symbionts, especially Portiera, to meet the nutritional demands of whiteflies. The results will inform efforts to control pests through manipulating symbionts in insect–symbiont associations.
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Parry H, Kalyebi A, Bianchi F, Sseruwagi P, Colvin J, Schellhorn N, Macfadyen S. Evaluation of cultural control and resistance-breeding strategies for suppression of whitefly infestation of cassava at the landscape scale: a simulation modeling approach. PEST MANAGEMENT SCIENCE 2020; 76:2699-2710. [PMID: 32162459 PMCID: PMC7383508 DOI: 10.1002/ps.5816] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 03/03/2020] [Accepted: 03/12/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND The whitefly Bemisia tabaci is an important vector of virus diseases, impacting cassava production in East Africa. To date, breeding efforts in this region have focused on disease resistance. Here we use a spatially-explicit simulation model to explore how breeding strategies for whitefly resistance will influence the population dynamics of whitefly in the context of regional variation in cassava crop management practices. RESULTS Simulations indicated that regions with a short cropping cycle and two cropping seasons per year were associated with high whitefly abundance. Nymph mortality and antixenosis resistance mechanisms were more effective than mechanisms that lead to longer whitefly development times. When spatial variation was introduced in heterogeneous landscapes, however, negative consequences of the antixenosis effect were observed in fields containing whitefly susceptible varieties, unless the proportion of whitefly resistant variety in the landscape was low (~10%) or the amount of matrix in the landscape was high (~75%). CONCLUSION We show the importance of considering cropping regime and landscape management context when developing and deploying whitefly-resistant cassava varieties. Recommendations differ significantly between regions. There may also be unintended negative consequences of higher whitefly densities for whitefly susceptible varieties if uptake of the new variety in a landscape is high, depending on the mechanism of resistance and the landscape context. Furthermore, we show that in some cases, such as where there is substantial fallow combined with a short single-season crop, the management characteristics of the existing cropping regime alone may be effective at controlling whitefly populations. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Hazel Parry
- CSIRO, Ecoscience PrecinctBrisbaneQueenslandAustralia
| | - Andrew Kalyebi
- National Crops Resources Research InstituteKampalaUganda
| | - Felix Bianchi
- Farming Systems Ecology, Wageningen University and ResearchWageningenThe Netherlands
| | - Peter Sseruwagi
- Tanzania Agricultural Research Institute – MikocheniDar es SalaamTanzania
| | | | | | - Sarina Macfadyen
- CSIRO, Black MountainCanberraAustralian Capital TerritoryAustralia
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Trebicki P. Climate change and plant virus epidemiology. Virus Res 2020; 286:198059. [PMID: 32561376 DOI: 10.1016/j.virusres.2020.198059] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 04/20/2020] [Accepted: 06/10/2020] [Indexed: 10/24/2022]
Abstract
Changes in global climate driven by anthropogenic activities, especially the burning of fossil fuels and deforestation, have been progressively increasing and are projected to intensify. Increasing concentrations of atmospheric carbon dioxide and temperature will have significant consequences for future food production, quality, distribution and security. The epidemiology of plant viruses will be altered in the future as a result of climate change. Elevated atmospheric carbon dioxide, increased temperature, changes to water availability and more frequent extreme weather events will have direct and indirect effects on plant viruses through changes in hosts and vectors. Predicted climatic changes will affect the distribution and survival of plant viruses and their vectors, which are expected to increase in many geographic regions. Furthermore, climate change can affect the virulence and pathogenicity of plant viruses, consequently increasing the frequency and scale of disease outbreaks. Thus, greater understanding of plant virus epidemiology is needed to better anticipate challenges ahead and to develop effective and robust control strategies that will aid in securing global food production for the future.
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Affiliation(s)
- Piotr Trebicki
- Agriculture Victoria, 110 Natimuk Rd, Horsham, Victoria, 3400, Australia.
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Donnelly R, Sikazwe GW, Gilligan CA. Estimating epidemiological parameters from experiments in vector access to host plants, the method of matching gradients. PLoS Comput Biol 2020; 16:e1007724. [PMID: 32176681 PMCID: PMC7098647 DOI: 10.1371/journal.pcbi.1007724] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2019] [Revised: 03/26/2020] [Accepted: 02/12/2020] [Indexed: 11/18/2022] Open
Abstract
Estimation of pathogenic life-history values, for instance the duration a pathogen is retained in an insect vector (i.e., retention period) is of particular importance for understanding plant disease epidemiology. How can we extract values for these epidemiological parameters from conventional small-scale laboratory experiments in which transmission success is measured in relation to durations of vector access to host plants? We provide a solution to this problem by deriving formulae for the empirical curves that these experiments produce, called access period response curves (i.e., transmission success vs access period). We do this by writing simple equations for the fundamental life-cycle components of insect vectors in the laboratory. We then infer values of epidemiological parameters by matching the theoretical and empirical gradients of access period response curves. Using the example of Cassava brown streak virus (CBSV), which has emerged in sub-Saharan Africa and now threatens regional food security, we illustrate the method of matching gradients. We show how applying the method to published data produces a new understanding of CBSV through the inference of retention period, acquisition period and inoculation period parameters. We found that CBSV is retained for a far shorter duration in its insect vector (Bemisia tabaci whitefly) than had previously been assumed. Our results shed light on a number of critical factors that may be responsible for the transition of CBSV from sub- to super-threshold R0 in sub-Saharan Africa. The method is applicable to plant pathogens in general, to supply epidemiological parameter estimates that are crucial for practical management of epidemics and prediction of pandemic risk. Cassava brown streak virus (CBSV), which was confined to coastal East Africa and the shores of Lake Malawi, has rapidly expanded its geographic range and now threatens regional food security. A recent laboratory experiment, in which vector access to plants infected with CBSV is varied, has provided plausible ranges for epidemiological parameters such as pathogen retention period (i.e., the duration that the pathogen is retained by the vector). In this work we introduce a new computational and mathematical framework for estimating epidemiological parameter values, instead of plausible ranges, from experiments in vector access to host plants. Since long distance carriage of insect vectors occurs within atmospheric air flows, the duration that the vector retains the pathogen (i.e., retention period) indirectly limits the scale of epidemics. Using our methods, we found that CBSV is retained for a far shorter duration than had previously been assumed. Our methods can be applied to the many experiments in vector access to host plants that have been conducted for numerous arthropod-transmitted plant pathogens across a range of genera. The ensuing epidemiological parameter estimates can be used in landscape computer simulations to predict epidemic risk and the prospects for control.
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Affiliation(s)
- Ruairí Donnelly
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
| | - Geofrey W. Sikazwe
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
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Irigoyen ML, Garceau DC, Bohorquez-Chaux A, Lopez-Lavalle LAB, Perez-Fons L, Fraser PD, Walling LL. Genome-wide analyses of cassava Pathogenesis-related (PR) gene families reveal core transcriptome responses to whitefly infestation, salicylic acid and jasmonic acid. BMC Genomics 2020; 21:93. [PMID: 31996126 PMCID: PMC6990599 DOI: 10.1186/s12864-019-6443-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 12/29/2019] [Indexed: 11/16/2022] Open
Abstract
Background Whiteflies are a threat to cassava (Manihot esculenta), an important staple food in many tropical/subtropical regions. Understanding the molecular mechanisms regulating cassava’s responses against this pest is crucial for developing control strategies. Pathogenesis-related (PR) protein families are an integral part of plant immunity. With the availability of whole genome sequences, the annotation and expression programs of the full complement of PR genes in an organism can now be achieved. An understanding of the responses of the entire complement of PR genes during biotic stress and to the defense hormones, salicylic acid (SA) and jasmonic acid (JA), is lacking. Here, we analyze the responses of cassava PR genes to whiteflies, SA, JA, and other biotic aggressors. Results The cassava genome possesses 14 of the 17 plant PR families, with a total of 447 PR genes. A cassava PR gene nomenclature is proposed. Phylogenetic relatedness of cassava PR proteins to each other and to homologs in poplar, rice and Arabidopsis identified cassava-specific PR gene family expansions. The temporal programs of PR gene expression in response to the whitefly (Aleurotrachelus socialis) in four whitefly-susceptible cassava genotypes showed that 167 of the 447 PR genes were regulated after whitefly infestation. While the timing of PR gene expression varied, over 37% of whitefly-regulated PR genes were downregulated in all four genotypes. Notably, whitefly-responsive PR genes were largely coordinately regulated by SA and JA. The analysis of cassava PR gene expression in response to five other biotic stresses revealed a strong positive correlation between whitefly and Xanthomonas axonopodis and Cassava Brown Streak Virus responses and negative correlations between whitefly and Cassava Mosaic Virus responses. Finally, certain associations between PR genes in cassava expansions and response to biotic stresses were observed among PR families. Conclusions This study represents the first genome-wide characterization of PR genes in cassava. PR gene responses to six biotic stresses and to SA and JA are demonstrably different to other angiosperms. We propose that our approach could be applied in other species to fully understand PR gene regulation by pathogens, pests and the canonical defense hormones SA and JA.
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Affiliation(s)
- Maria L Irigoyen
- Department of Botany and Plant Sciences and Institute of Integrative Genome Biology, University of California, Riverside, CA, 92521, USA
| | - Danielle C Garceau
- Department of Botany and Plant Sciences and Institute of Integrative Genome Biology, University of California, Riverside, CA, 92521, USA
| | | | | | - Laura Perez-Fons
- Department of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Paul D Fraser
- Department of Biological Sciences, Royal Holloway University of London, Egham, UK
| | - Linda L Walling
- Department of Botany and Plant Sciences and Institute of Integrative Genome Biology, University of California, Riverside, CA, 92521, USA.
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Wainaina JM, Ateka E, Makori T, Kehoe MA, Boykin LM. A metagenomic study of DNA viruses from samples of local varieties of common bean in Kenya. PeerJ 2019; 7:e6465. [PMID: 30891366 PMCID: PMC6422016 DOI: 10.7717/peerj.6465] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 01/16/2019] [Indexed: 11/20/2022] Open
Abstract
Common bean (Phaseolus vulgaris L.) is the primary source of protein and nutrients in the majority of households in sub-Saharan Africa. However, pests and viral diseases are key drivers in the reduction of bean production. To date, the majority of viruses reported in beans have been RNA viruses. In this study, we carried out a viral metagenomic analysis on virus symptomatic bean plants. Our virus detection pipeline identified three viral fragments of the double-stranded DNA virus Pelargonium vein banding virus (PVBV) (family, Caulimoviridae, genus Badnavirus). This is the first report of the dsDNA virus and specifically PVBV in legumes to our knowledge. In addition two previously reported +ssRNA viruses the bean common mosaic necrosis virus (BCMNVA) (Potyviridae) and aphid lethal paralysis virus (ALPV) (Dicistroviridae) were identified. Bayesian phylogenetic analysis of the Badnavirus (PVBV) using amino acid sequences of the RT/RNA-dependent DNA polymerase region showed the Kenyan sequence (SRF019_MK014483) was closely matched with two Badnavirus viruses: Dracaena mottle virus (DrMV) (YP_610965) and Lucky bamboo bacilliform virus (ABR01170). Phylogenetic analysis of BCMNVA was based on amino acid sequences of the Nib region. The BCMNVA phylogenetic tree resolved two clades identified as clade (I and II). Sequence from this study SRF35_MK014482, clustered within clade I with other Kenyan sequences. Conversely, Bayesian phylogenetic analysis of ALPV was based on nucleotide sequences of the hypothetical protein gene 1 and 2. Three main clades were resolved and identified as clades I-III. The Kenyan sequence from this study (SRF35_MK014481) clustered within clade II, and nested within a sub-clade; comprising of sequences from China and an earlier ALPV sequences from Kenya isolated from maize (MF458892). Our findings support the use of viral metagenomics to reveal the nascent viruses, their viral diversity and evolutionary history of these viruses. The detection of ALPV and PVBV indicate that these viruses have likely been underreported due to the unavailability of diagnostic tools.
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Affiliation(s)
- James M Wainaina
- School of Molecular Sciences and Australian Research Council Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, WA, Australia
| | - Elijah Ateka
- Department of Horticulture, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
| | - Timothy Makori
- Department of Horticulture, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
| | - Monica A Kehoe
- Diagnostic Laboratory Service, Plant Pathology, Department of Primary Industries and Regional Development, South Perth, WA, Australia
| | - Laura M Boykin
- School of Molecular Sciences and Australian Research Council Centre of Excellence in Plant Energy Biology, The University of Western Australia, Crawley, WA, Australia
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Tay WT, Gordon KHJ. Going global - genomic insights into insect invasions. CURRENT OPINION IN INSECT SCIENCE 2019; 31:123-130. [PMID: 31109665 DOI: 10.1016/j.cois.2018.12.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 12/03/2018] [Accepted: 12/05/2018] [Indexed: 06/09/2023]
Abstract
The spread of invasive insect pests is becoming an increasing problem for agriculture globally. We discuss a number of invasive insects, already of major economic significance that have recently expanded their range to become truly global threats. These include the noctuid moths Helicoverpa and Spodoptera, whose caterpillars have long been among the worst pests in their native Old and New World habitats, respectively, and the whitefly Bemisia, a major vector of plant virus diseases. Importantly, genomic resources for these species have recently become available, allowing research to move beyond the restrictions imposed by earlier approaches limited to a single or few mitochondrial and nuclear markers, to employ genome-wide genotyping and resequencing protocols. These studies have shown hybridisation within the various species complexes, identified regions under selection in agricultural environments, and enable monitoring of genes important as biosecurity risks through introgression into established populations free of the genes. In all cases studied, global trade has emerged as the probable cause of insect spread, making it ever more important that biosecurity protocols and agencies work with researchers to make the most effective use of emerging genomic resources and tools.
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Affiliation(s)
- Wee Tek Tay
- CSIRO Black Mountain Laboratories, Clunies Ross Street, ACT 2601, Australia
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Kalyebi A, Macfadyen S, Parry H, Tay WT, De Barro P, Colvin J. African cassava whitefly, Bemisia tabaci, cassava colonization preferences and control implications. PLoS One 2018; 13:e0204862. [PMID: 30300388 PMCID: PMC6177144 DOI: 10.1371/journal.pone.0204862] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/14/2018] [Indexed: 11/19/2022] Open
Abstract
Cassava is a staple food for people across sub-Saharan Africa. Over the last 20 years, there has been an increased frequency of outbreaks and crop damage in this region caused by the cassava-adapted Bemisia tabaci putative species. Little is known about when and why B. tabaci adults move and colonize new cassava crops, especially in farming systems that contain a mixture of cultivar types and plant ages. Here, we assessed experimentally whether the age and variety of cassava affected the density of B. tabaci. We also tested whether the age and variety of the source cassava field affected the variety preference of B. tabaci when they colonized new cassava plants. We placed uninfested potted "sentinel" plants of three cassava varieties (Nam 130, Nase 14, and Njule Red) in source fields containing one of two varieties (Nam 130 or Nase 14) and one of three age classes (young, medium, or old). After two weeks, the numbers of nymphs on the sentinel plants were used as a measure of colonization. Molecular identification revealed that the B. tabaci species was sub-Saharan Africa 1 (SSA1). We found a positive correlation between the density of nymphs on sentinel plants and the density of adults in the source field. The density of nymphs on the sentinels was not significantly related to the age of the source field. Bemisia tabaci adults did not preferentially colonize the sentinel plant of the same variety as the source field. There was a significant interactive effect, however, between the source and sentinel variety that may indicate variability in colonization. We conclude that managing cassava source fields to reduce B. tabaci abundance will be more effective than manipulating nearby varieties. We also suggest that planting a "whitefly sink" variety is unlikely to reduce B. tabaci SSA1 populations unless fields are managed to reduce B. tabaci densities using other integrative approaches.
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Affiliation(s)
- Andrew Kalyebi
- National Crops Resources Research Institute, Kampala, Uganda
- Mikocheni Agricultural Research Institute, Dar es Salaam, Tanzania
| | | | - Hazel Parry
- CSIRO Ecosciences Precinct, Brisbane QLD, Australia
| | - Wee Tek Tay
- CSIRO, Clunies Ross St, Acton, ACT, Australia
| | | | - John Colvin
- Natural Resources Institute, University of Greenwich, Chatham Maritime, Kent, United Kingdom
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Incidence of cassava mosaic disease and associated whitefly vectors in South West and North Central Nigeria: Data exploration. Data Brief 2018; 19:370-392. [PMID: 29892658 PMCID: PMC5993015 DOI: 10.1016/j.dib.2018.05.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/04/2018] [Indexed: 11/20/2022] Open
Abstract
Cassava mosaic disease (CMD) is one of the most economically important viral diseases of cassava, an important staple food for over 800 million people in the tropics. Although several Cassava mosaic virus species associated with CMD have been isolated and characterized over the years, several new super virulent strains of these viruses have evolved due to genetic recombination between diverse species. In this data article, field survey data collected from 184 cassava farms in 12 South Western and North Central States of Nigeria in 2015 are presented and extensively explored. In each State, one cassava farm was randomly selected as the first farm and subsequent farms were selected at 10 km intervals, except in locations were cassava farms are sporadically located. In each selected farm, 30 cassava plants were sampled along two diagonals and all selected plant was scored for the presence or absence of CMD symptoms. Cassava mosaic disease incidence and associated whitefly vectors in South West and North Central Nigeria are explored using relevant descriptive statistics, box plots, bar charts, line graphs, and pie charts. In addition, correlation analysis, Analysis of Variance (ANOVA), and multiple comparison post-hoc tests are performed to understand the relationship between the numbers of whiteflies counted, uninfected farms, infected farms, and the mean of symptom severity in and across the States under investigation. The data exploration provided in this data article is considered adequate for objective assessment of the incidence and symptom severity of cassava mosaic disease and associated whitefly vectors in farmers' fields in these parts of Nigeria where cassava is heavily cultivated.
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