1
|
Alicai T, Szyniszewska AM, Omongo CA, Abidrabo P, Okao-Okuja G, Baguma Y, Ogwok E, Kawuki R, Esuma W, Tairo F, Bua A, Legg JP, Stutt ROJH, Godding D, Sseruwagi P, Ndunguru J, Gilligan CA. Expansion of the cassava brown streak pandemic in Uganda revealed by annual field survey data for 2004 to 2017. Sci Data 2019; 6:327. [PMID: 31852893 PMCID: PMC6920376 DOI: 10.1038/s41597-019-0334-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 11/26/2019] [Indexed: 11/26/2022] Open
Abstract
Cassava brown streak disease (CBSD) is currently the most devastating cassava disease in eastern, central and southern Africa affecting a staple crop for over 700 million people on the continent. A major outbreak of CBSD in 2004 near Kampala rapidly spread across Uganda. In the following years, similar CBSD outbreaks were noted in countries across eastern and central Africa, and now the disease poses a threat to West Africa including Nigeria - the biggest cassava producer in the world. A comprehensive dataset with 7,627 locations, annually and consistently sampled between 2004 and 2017 was collated from historic paper and electronic records stored in Uganda. The survey comprises multiple variables including data for incidence and symptom severity of CBSD and abundance of the whitefly vector (Bemisia tabaci). This dataset provides a unique basis to characterize the epidemiology and dynamics of CBSD spread in order to inform disease surveillance and management. We also describe methods used to integrate and verify extensive field records for surveys typical of emerging epidemics in subsistence crops.
Collapse
Affiliation(s)
- Titus Alicai
- National Crops Resources Research Institute, Kampala, Uganda
| | - Anna M Szyniszewska
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | | | | | | | - Yona Baguma
- National Crops Resources Research Institute, Kampala, Uganda
| | - Emmanuel Ogwok
- National Crops Resources Research Institute, Kampala, Uganda
| | - Robert Kawuki
- National Crops Resources Research Institute, Kampala, Uganda
| | - Williams Esuma
- National Crops Resources Research Institute, Kampala, Uganda
| | - Fred Tairo
- Mikocheni Agricultural Research Institute, Dares Salaam, Tanzania
| | - Anton Bua
- National Crops Resources Research Institute, Kampala, Uganda
| | - James P Legg
- International Institute of Tropical Agriculture, Dares Salaam, Tanzania
| | - Richard O J H Stutt
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
| | - David Godding
- Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom
- Farming Data, Cambridge, United Kingdom
| | - Peter Sseruwagi
- Mikocheni Agricultural Research Institute, Dares Salaam, Tanzania
| | - Joseph Ndunguru
- Mikocheni Agricultural Research Institute, Dares Salaam, Tanzania
| | | |
Collapse
|
2
|
Kawuki RS, Kaweesi T, Esuma W, Pariyo A, Kayondo IS, Ozimati A, Kyaligonza V, Abaca A, Orone J, Tumuhimbise R, Nuwamanya E, Abidrabo P, Amuge T, Ogwok E, Okao G, Wagaba H, Adiga G, Alicai T, Omongo C, Bua A, Ferguson M, Kanju E, Baguma Y. Eleven years of breeding efforts to combat cassava brown streak disease. Breed Sci 2016; 66:560-571. [PMID: 27795681 PMCID: PMC5010303 DOI: 10.1270/jsbbs.16005] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/07/2016] [Indexed: 05/05/2023]
Abstract
Cassava (Manihot esculenta Crantz) production is currently under threat from cassava brown streak disease (CBSD), a disease that is among the seven most serious obstacles to world's food security. Three issues are of significance for CBSD. Firstly, the virus associated with CBSD, has co-evolved with cassava outside its center of origin for at least 90 years. Secondly, that for the last 74 years, CBSD was only limited to the low lands. Thirdly, that most research has largely focused on CBSD epidemiology and virus diversity. Accordingly, this paper focuses on CBSD genetics and/or breeding and hence, presents empirical data generated in the past 11 years of cassava breeding in Uganda. Specifically, this paper provides: 1) empirical data on CBSD resistance screening efforts to identify sources of resistance and/or tolerance; 2) an update on CBSD resistance population development comprising of full-sibs, half-sibs and S1 families and their respective field performances; and 3) insights into chromosomal regions and genes involved in CBSD resistance based on genome wide association analysis. It is expected that this information will provide a foundation for harmonizing on-going CBSD breeding efforts and consequently, inform the future breeding interventions aimed at combating CBSD.
Collapse
Affiliation(s)
- Robert Sezi Kawuki
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Tadeo Kaweesi
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Williams Esuma
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Anthony Pariyo
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Ismail Siraj Kayondo
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Alfred Ozimati
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Vincent Kyaligonza
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Alex Abaca
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Joseph Orone
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Robooni Tumuhimbise
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Ephraim Nuwamanya
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Philip Abidrabo
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Teddy Amuge
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Emmanuel Ogwok
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Geoffrey Okao
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Henry Wagaba
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Gerald Adiga
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Titus Alicai
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Christopher Omongo
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Anton Bua
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| | - Morag Ferguson
- International Institute of Tropical Agriculture (IITA), C/o International Livestock Research Institute (ILRI),
P.O. Box 30709, Nairobi 00100,
Kenya
| | - Edward Kanju
- International Institute of Tropical Agriculture (IITA),
P.O. Box 34441, Dar es Salaam,
Tanzania
| | - Yona Baguma
- National Crops Resources Research Institute,
9 km Gayaza-Zirobwe Road, P.O. Box 7084, Kampala,
Uganda
| |
Collapse
|
3
|
Ogwok E, Ilyas M, Alicai T, Rey MEC, Taylor NJ. Comparative analysis of virus-derived small RNAs within cassava (Manihot esculenta Crantz) infected with cassava brown streak viruses. Virus Res 2016; 215:1-11. [PMID: 26811902 PMCID: PMC4796025 DOI: 10.1016/j.virusres.2016.01.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 01/18/2016] [Accepted: 01/21/2016] [Indexed: 01/02/2023]
Abstract
The 21-nt virus-derived small RNAs were predominant, followed by the 22-nt class. Susceptible cassava genotypes accumulated higher CBSV- than UCBSV-derived small RNA. Tolerant cassava genotype accumulated high CBSV- and low UCBSV-derived small RNAs. AGO2, DCL2 and DCL4 were differentially regulated in CBSV/UCBSV-infected plants. CBSV and UCBSV interact differently in the same host genetic background
Infection of plant cells by viral pathogens triggers RNA silencing, an innate antiviral defense mechanism. In response to infection, small RNAs (sRNAs) are produced that associate with Argonaute (AGO)-containing silencing complexes which act to inactivate viral genomes by posttranscriptional gene silencing (PTGS). Deep sequencing was used to compare virus-derived small RNAs (vsRNAs) in cassava genotypes NASE 3, TME 204 and 60444 infected with the positive sense single-stranded RNA (+ssRNA) viruses cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), the causal agents of cassava brown streak disease (CBSD). An abundance of 21–24 nt vsRNAs was detected and mapped, covering the entire CBSV and UCBSV genomes. The 21 nt vsRNAs were most predominant, followed by the 22 nt class with a slight bias toward sense compared to antisense polarity, and a bias for adenine and uracil bases present at the 5′-terminus. Distribution and frequency of vsRNAs differed between cassava genotypes and viral genomes. In susceptible genotypes TME 204 and 60444, CBSV-derived sRNAs were seen in greater abundance than UCBSV-derived sRNAs. NASE 3, known to be resistant to UCBSV, accumulated negligible UCBSV-derived sRNAs but high populations of CBSV-derived sRNAs. Transcript levels of cassava homologues of AGO2, DCL2 and DCL4, which are central to the gene-silencing complex, were found to be differentially regulated in CBSV- and UCBSV-infected plants across genotypes, suggesting these proteins play a role in antiviral defense. Irrespective of genotype or viral pathogen, maximum populations of vsRNAs mapped to the cytoplasmic inclusion, P1 and P3 protein-encoding regions. Our results indicate disparity between CBSV and UCBSV host-virus interaction mechanisms, and provide insight into the role of virus-induced gene silencing as a mechanism of resistance to CBSD.
Collapse
Affiliation(s)
- Emmanuel Ogwok
- National Crops Resources Research Institute, Namulonge, P.O Box 7084, Kampala, Uganda; Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA; School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, P.O Wits 2050, Johannesburg, South Africa
| | - Muhammad Ilyas
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
| | - Titus Alicai
- National Crops Resources Research Institute, Namulonge, P.O Box 7084, Kampala, Uganda
| | - Marie E C Rey
- School of Molecular and Cell Biology, University of the Witwatersrand, Private Bag 3, P.O Wits 2050, Johannesburg, South Africa
| | - Nigel J Taylor
- Institute for International Crop Improvement, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
| |
Collapse
|
4
|
Odipio J, Ogwok E, Taylor NJ, Halsey M, Bua A, Fauquet CM, Alicai T. RNAi-derived field resistance to Cassava brown streak disease persists across the vegetative cropping cycle. GM Crops Food 2014; 5:16-9. [PMID: 24296511 PMCID: PMC5033198 DOI: 10.4161/gmcr.26408] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 09/03/2013] [Accepted: 09/07/2013] [Indexed: 11/19/2022]
Abstract
A confined field trial was established to determine durability of RNAi-mediated resistance to Cassava brown streak disease (CBSD). Stem cuttings were obtained from field-grown cassava plants of cv 60444 transgenic for construct p718, consisting of an 894 bp inverted repeat sequence from the Ugandan Cassava brown streak virus (UCBSV) coat protein. Plants were established from three transgenic lines previously shown to provide complete resistance to UCBSV and differing levels of protection to the non-homologous virus species Cassava brown streak virus (CBSV), and grown for 11 months. CBSD symptoms were observed on shoots and storage roots of all non-transgenic cv 60444 control plants and transgenic lines p718-002 and p718-005, but not on p718-001. RT-PCR diagnostic showed tissues of plant lines p718-002 and p718-005 to be infected with CBSV, but free of UCBSV. All leaves and roots of p718-001 plants were to carry no detectable levels of either pathogen. Plants of cv 60444 in this field trial showed severe cassava mosaic disease symptoms, indicating that presence of replicating geminiviruses did not cause significant suppression of RNAi-mediated resistance to CBSD. Resistance to CBSD across a vegetative cropping cycle confirms earlier field data, and provides an important step in proof of concept for application of RNAi technology to control of CBSD under conditions encountered in farmers' fields.
Collapse
Affiliation(s)
- John Odipio
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
| | - Emmanuel Ogwok
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Nigel J Taylor
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Mark Halsey
- Institute for International Crop Improvement; Donald Danforth Plant Science Center; St. Louis, MO USA
| | - Anton Bua
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
| | - Claude M Fauquet
- Centro Internacional de Agricultura Tropical; Cali-Palmira; Cali, Colombia
| | - Titus Alicai
- National Crops Resources Research Institute; Namulonge; Kampala, Uganda
| |
Collapse
|
5
|
Ogwok E, Odipio J, Halsey M, Gaitán-Solís E, Bua A, Taylor NJ, Fauquet CM, Alicai T. Transgenic RNA interference (RNAi)-derived field resistance to cassava brown streak disease. Mol Plant Pathol 2012; 13:1019-31. [PMID: 22845735 PMCID: PMC6638741 DOI: 10.1111/j.1364-3703.2012.00812.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Cassava brown streak disease (CBSD), caused by the Ipomoviruses Cassava brown streak virus (CBSV) and Ugandan Cassava brown streak virus (UCBSV), is considered to be an imminent threat to food security in tropical Africa. Cassava plants were transgenically modified to generate small interfering RNAs (siRNAs) from truncated full-length (894-bp) and N-terminal (402-bp) portions of the UCBSV coat protein (ΔCP) sequence. Seven siRNA-producing lines from each gene construct were tested under confined field trials at Namulonge, Uganda. All nontransgenic control plants (n = 60) developed CBSD symptoms on aerial tissues by 6 months after planting, whereas plants transgenic for the full-length ΔCP sequence showed a 3-month delay in disease development, with 98% of clonal replicates within line 718-001 remaining symptom free over the 11-month trial. Reverse transcriptase-polymerase chain reaction (RT-PCR) diagnostics indicated the presence of UCBSV within the leaves of 57% of the nontransgenic controls, but in only two of 413 plants tested (0.5%) across the 14 transgenic lines. All transgenic plants showing CBSD were PCR positive for the presence of CBSV, except for line 781-001, in which 93% of plants were confirmed to be free of both pathogens. At harvest, 90% of storage roots from nontransgenic plants were severely affected by CBSD-induced necrosis. However, transgenic lines 718-005 and 718-001 showed significant suppression of disease, with 95% of roots from the latter line remaining free from necrosis and RT-PCR negative for the presence of both viral pathogens. Cross-protection against CBSV by siRNAs generated from the full-length UCBSV ΔCP confirms a previous report in tobacco. The information presented provides proof of principle for the control of CBSD by RNA interference-mediated technology, and progress towards the potential control of this damaging disease.
Collapse
Affiliation(s)
- Emmanuel Ogwok
- National Crops Resources Research Institute, Namulonge, Kampala, Uganda
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Yadav JS, Ogwok E, Wagaba H, Patil BL, Bagewadi B, Alicai T, Gaitan-Solis E, Taylor NJ, Fauquet CM. RNAi-mediated resistance to Cassava brown streak Uganda virus in transgenic cassava. Mol Plant Pathol 2011; 12:677-87. [PMID: 21726367 PMCID: PMC6640337 DOI: 10.1111/j.1364-3703.2010.00700.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Cassava brown streak disease (CBSD), caused by Cassava brown streak Uganda virus (CBSUV) and Cassava brown streak virus (CBSV), is of new epidemic importance to cassava (Manihot esculenta Crantz) production in East Africa, and an emerging threat to the crop in Central and West Africa. This study demonstrates that at least one of these two ipomoviruses, CBSUV, can be efficiently controlled using RNA interference (RNAi) technology in cassava. An RNAi construct targeting the near full-length coat protein (FL-CP) of CBSUV was expressed constitutively as a hairpin construct in cassava. Transgenic cassava lines expressing small interfering RNAs (siRNAs) against this sequence showed 100% resistance to CBSUV across replicated graft inoculation experiments. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed the presence of CBSUV in leaves and some tuberous roots from challenged controls, but not in the same tissues from transgenic plants. This is the first demonstration of RNAi-mediated resistance to the ipomovirus CBSUV in cassava.
Collapse
Affiliation(s)
- Jitender S Yadav
- International Laboratory for Tropical Agricultural Biotechnology, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Patil BL, Ogwok E, Wagaba H, Mohammed IU, Yadav JS, Bagewadi B, Taylor NJ, Kreuze JF, Maruthi MN, Alicai T, Fauquet CM. RNAi-mediated resistance to diverse isolates belonging to two virus species involved in Cassava brown streak disease. Mol Plant Pathol 2011; 12:31-41. [PMID: 21118347 PMCID: PMC6640250 DOI: 10.1111/j.1364-3703.2010.00650.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Cassava brown streak disease (CBSD) is emerging as one of the most important viral diseases of cassava (Manihot esculenta) and is considered today as the biggest threat to cassava cultivation in East Africa. The disease is caused by isolates of at least two phylogenetically distinct species of single-stranded RNA viruses belonging to the family Potyviridae, genus Ipomovirus. The two species are present predominantly in the coastal lowland [Cassava brown streak virus (CBSV); Tanzania and Mozambique] and highland [Cassava brown streak Uganda virus (CBSUV); Lake Victoria Basin, Uganda, Kenya and Malawi] in East Africa. In this study, we demonstrate that CBSD can be efficiently controlled using RNA interference (RNAi). Three RNAi constructs targeting the highland species were generated, consisting of the full-length (FL; 894 nucleotides), 397-nucleotide N-terminal and 491-nucleotide C-terminal portions of the coat protein (CP) gene of a Ugandan isolate of CBSUV (CBSUV-[UG:Nam:04]), and expressed constitutively in Nicotiana benthamiana. After challenge with CBSUV-[UG:Nam:04], plants homozygous for FL-CP showed the highest resistance, followed by the N-terminal and C-terminal lines with similar resistance. In the case of FL, approximately 85% of the transgenic plant lines produced were completely resistant. Some transgenic lines were also challenged with six distinct isolates representing both species: CBSV and CBSUV. In addition to nearly complete resistance to the homologous virus, two FL plant lines showed 100% resistance and two C-terminal lines expressed 50-100% resistance, whereas the N-terminal lines succumbed to the nonhomologous CBSV isolates. Northern blotting revealed a positive correlation between the level of transgene-specific small interfering RNAs detected in transgenic plants and the level of virus resistance. This is the first demonstration of RNAi-mediated resistance to CBSD and protection across very distant isolates (more than 25% in nucleotide sequence) belonging to two different species: Cassava brown streak virus and Cassava brown streak Uganda virus.
Collapse
MESH Headings
- Africa, Eastern
- Host-Pathogen Interactions/genetics
- Manihot/genetics
- Manihot/virology
- Plant Diseases/genetics
- Plant Diseases/prevention & control
- Plant Diseases/virology
- Plants, Genetically Modified
- Potyviridae/classification
- Potyviridae/genetics
- Potyviridae/pathogenicity
- RNA Interference
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Small Interfering/genetics
- RNA, Small Interfering/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Species Specificity
- Nicotiana/genetics
- Nicotiana/virology
- Virulence/genetics
Collapse
Affiliation(s)
- Basavaprabhu L Patil
- International Laboratory for Tropical Agricultural Biotechnology, Donald Danforth Plant Science Center, St. Louis, MO 63132, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Ogwok E, Patil BL, Alicai T, Fauquet CM. Transmission studies with Cassava brown streak Uganda virus (Potyviridae: Ipomovirus) and its interaction with abiotic and biotic factors in Nicotiana benthamiana. J Virol Methods 2010; 169:296-304. [PMID: 20691215 DOI: 10.1016/j.jviromet.2010.07.030] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 07/20/2010] [Accepted: 07/26/2010] [Indexed: 10/19/2022]
Abstract
Cassava brown streak disease (CBSD), caused by two distinct species, Cassava brown streak Uganda virus (CBSUV) and Cassava brown streak virus (CBSV), is a major constraint to cassava (Manihot esculenta Crantz) production in Africa. Absence of infectious clones of CBSUV or CBSV and the lack of efficient means of mechanical transmission of CBSD has hampered laboratory studies of this disease. Mechanical transmission, achieved mainly by plant sap inoculation, is a widely used technique for characterizing plant viruses. Efficient sap transmission of CBSUV/CBSV to the common laboratory host Nicotiana benthamiana is essential for both basic and applied studies of the virus. We report here the development of an efficient protocol for sap transmission of CBSUV to N. benthamiana and N. debneyi. Several factors affecting transmission efficiency were identified such as the effects of buffer composition, antioxidants, inoculum concentration, plant age and temperature. Higher temperatures (30 °C) favored rapid symptom initiation compared to lower temperatures (21 °C) when sap prepared in phosphate buffer of pH 7.0 was applied on the leaves of N. benthamiana dusted with the abrasive (carborundum). We demonstrated the usefulness of the transmission method in transient evaluation of CBSUV[UG:Nam:04]-derived RNA interference constructs for CBSD resistance and also in studying the interaction of CBSUV[UG:Nam:04] with cassava mosaic geminiviruses, another important group of viruses infecting cassava.
Collapse
Affiliation(s)
- Emmanuel Ogwok
- International Laboratory for Tropical Agricultural Biotechnology, Donald Danforth Plant Science Center, 975 N. Warson Road, St. Louis, MO 63132, USA
| | | | | | | |
Collapse
|