1
|
Katati B, Kovács S, Njapau H, Kachapulula PW, Zwaan BJ, van Diepeningen AD, Schoustra SE. Maize Aspergillus section Flavi isolate diversity may be distinct from that of soil and subsequently the source of aflatoxin contamination. Mycotoxin Res 2024:10.1007/s12550-024-00532-7. [PMID: 38647834 DOI: 10.1007/s12550-024-00532-7] [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: 07/15/2023] [Revised: 03/17/2024] [Accepted: 03/20/2024] [Indexed: 04/25/2024]
Abstract
Aspergillus section Flavi (Flavi) is a diverse group of fungal species whose common members include A. flavus and A. parasiticus. These are well-known for the production of aflatoxin (AF) B and G and other toxic metabolites, like cyclopiazonic acid (CPA). They are saprophytic soil dwellers and also become crop opportunistic epiphytes. The consequence is contamination of the crop with mycotoxins, such as carcinogenic AF. We investigated the Flavi community structure of maize and that of their surrounding soil, including their mycotoxigenicity. Furthermore, we investigated the link of the maize Flavi diversity with preharvest maize AF levels. The study was carried out in four selected districts of Zambia, in a low rainfall zone. The Flavi characterisation was triphasic, involving morphological (colony colour and sclerotia formation), metabolic (AF and CPA production) and genetic (calmodulin gene polymorphism) analyses. Flavi abundance was determined by dilution plate technique on modified rose Bengal agar. Results showed that Flavi communities on maize and in soil differed. Maize had a higher Flavi species diversity than soil. A. parasiticus dominated the soil community by frequency of field appearance (85%), while maize was dominated by A. minisclerotigenes (45%). CPA-producers with or without AF production dominated the maize (65%) while producers of only AF (B/G) dominated the soil (88%). The ratio between maize A. parasiticus and A. minisclerotigenes abundance seemed to have had a bearing on the levels of AF in maize, with a ratio close to 1:1 having higher levels than a pure community of either A. parasiticus or A. minisclerotigenes.
Collapse
Affiliation(s)
- Bwalya Katati
- Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands.
- Mycotoxicology Laboratory, National Institute for Scientific and Industrial Research, Lusaka, Zambia.
| | - Stan Kovács
- Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands
| | - Henry Njapau
- Mycotoxicology Laboratory, National Institute for Scientific and Industrial Research, Lusaka, Zambia
| | | | - Bas J Zwaan
- Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands
| | - Anne D van Diepeningen
- Biointeractions and Plant Health, Wageningen University and Research, Wageningen, The Netherlands
| | - Sijmen E Schoustra
- Laboratory of Genetics, Wageningen University and Research, Wageningen, The Netherlands
- School of Agricultural Sciences, University of Zambia, Lusaka, Zambia
| |
Collapse
|
2
|
Ouadhene MA, Callicott KA, Ortega‐Beltran A, Mehl HL, Cotty PJ, Battilani P. Structure of Aspergillus flavus populations associated with maize in Greece, Spain, and Serbia: Implications for aflatoxin biocontrol on a regional scale. ENVIRONMENTAL MICROBIOLOGY REPORTS 2024; 16:e13249. [PMID: 38634243 PMCID: PMC11024511 DOI: 10.1111/1758-2229.13249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 03/12/2024] [Indexed: 04/19/2024]
Abstract
Aspergillus flavus is the most frequently identified producer of aflatoxins. Non-aflatoxigenic members of the A. flavus L strains are used in various continents as active ingredients of bioprotectants directed at preventing aflatoxin contamination by competitive displacement of aflatoxin producers. The current research examined the genetic diversity of A. flavus L strain across southern Europe to gain insights into the population structure and evolution of this species and to evaluate the prevalence of genotypes closely related to MUCL54911, the active ingredient of AF-X1. A total of 2173L strain isolates recovered from maize collected across Greece, Spain, and Serbia in 2020 and 2021 were subjected to simple sequence repeat (SSR) genotyping. The analysis revealed high diversity within and among countries and dozens of haplotypes shared. Linkage disequilibrium analysis indicated asexual reproduction and clonal evolution of A. flavus L strain resident in Europe. Moreover, haplotypes closely related to MUCL54911 were found to belong to the same vegetative compatibility group (VCG) IT006 and were relatively common in all three countries. The results indicate that IT006 is endemic to southern Europe and may be utilized as an aflatoxin mitigation tool for maize across the region without concern for potential adverse impacts associated with the introduction of an exotic microorganism.
Collapse
Affiliation(s)
- Mohamed Ali Ouadhene
- Department of Sustainable Crop ProductionUniversità Cattolica del Sacro CuorePiacenzaItaly
| | | | | | | | - Peter J. Cotty
- College of Food Science and EngineeringOcean University of ChinaQingdaoChina
| | - Paola Battilani
- Department of Sustainable Crop ProductionUniversità Cattolica del Sacro CuorePiacenzaItaly
| |
Collapse
|
3
|
Chen X, Abdallah MF, Landschoot S, Audenaert K, De Saeger S, Chen X, Rajkovic A. Aspergillus flavus and Fusarium verticillioides and Their Main Mycotoxins: Global Distribution and Scenarios of Interactions in Maize. Toxins (Basel) 2023; 15:577. [PMID: 37756003 PMCID: PMC10534665 DOI: 10.3390/toxins15090577] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 08/25/2023] [Accepted: 09/04/2023] [Indexed: 09/28/2023] Open
Abstract
Maize is frequently contaminated with multiple mycotoxins, especially those produced by Aspergillus flavus and Fusarium verticillioides. As mycotoxin contamination is a critical factor that destabilizes global food safety, the current review provides an updated overview of the (co-)occurrence of A. flavus and F. verticillioides and (co-)contamination of aflatoxin B1 (AFB1) and fumonisin B1 (FB1) in maize. Furthermore, it summarizes their interactions in maize. The gathered data predict the (co-)occurrence and virulence of A. flavus and F. verticillioides would increase worldwide, especially in European cold climate countries. Studies on the interaction of both fungi regarding their growth mainly showed antagonistic interactions in vitro or in planta conditions. However, the (co-)contamination of AFB1 and FB1 has risen worldwide in the last decade. Primarily, this co-contamination increased by 32% in Europe (2010-2020 vs. 1992-2009). This implies that fungi and mycotoxins would severely threaten European-grown maize.
Collapse
Affiliation(s)
- Xiangrong Chen
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (M.F.A.); (A.R.)
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (S.L.); (K.A.)
| | - Mohamed F. Abdallah
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (M.F.A.); (A.R.)
- Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, Assiut University, Assiut 71515, Egypt
| | - Sofie Landschoot
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (S.L.); (K.A.)
| | - Kris Audenaert
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (S.L.); (K.A.)
| | - Sarah De Saeger
- Centre of Excellence in Mycotoxicology and Public Health, Department of Bioanalysis, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium;
- Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, Doornfontein Campus, P.O. Box 17011, Gauteng 2028, South Africa
| | - Xiangfeng Chen
- Shandong Analysis and Test Centre, Qilu University of Technology (Shandong Academy of Science), Jinan 250014, China;
| | - Andreja Rajkovic
- Department of Food Technology, Safety and Health, Faculty of Bioscience Engineering, Ghent University, 9000 Ghent, Belgium; (M.F.A.); (A.R.)
| |
Collapse
|
4
|
Atehnkeng J, Ojiambo PS, Ortega-Beltran A, Augusto J, Cotty PJ, Bandyopadhyay R. Impact of frequency of application on the long-term efficacy of the biocontrol product Aflasafe in reducing aflatoxin contamination in maize. Front Microbiol 2022; 13:1049013. [PMID: 36504767 PMCID: PMC9732863 DOI: 10.3389/fmicb.2022.1049013] [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: 09/20/2022] [Accepted: 10/31/2022] [Indexed: 11/25/2022] Open
Abstract
Aflatoxins, produced by several Aspergillus section Flavi species in various crops, are a significant public health risk and a barrier to trade and development. In sub-Saharan Africa, maize and groundnut are particularly vulnerable to aflatoxin contamination. Aflasafe, a registered aflatoxin biocontrol product, utilizes atoxigenic A. flavus genotypes native to Nigeria to displace aflatoxin producers and mitigate aflatoxin contamination. Aflasafe was evaluated in farmers' fields for 3 years, under various regimens, to quantify carry-over of the biocontrol active ingredient genotypes. Nine maize fields were each treated either continuously for 3 years, the first two successive years, in year 1 and year 3, or once during the first year. For each treated field, a nearby untreated field was monitored. Aflatoxins were quantified in grain at harvest and after simulated poor storage. Biocontrol efficacy and frequencies of the active ingredient genotypes decreased in the absence of annual treatment. Maize treated consecutively for 2 or 3 years had significantly (p < 0.05) less aflatoxin (92% less) in grain at harvest than untreated maize. Maize grain from treated fields subjected to simulated poor storage had significantly less (p < 0.05) aflatoxin than grain from untreated fields, regardless of application regimen. Active ingredients occurred at higher frequencies in soil and grain from treated fields than from untreated fields. The incidence of active ingredients recovered in soil was significantly correlated (r = 0.898; p < 0.001) with the incidence of active ingredients in grain, which in turn was also significantly correlated (r = -0.621, p = 0.02) with aflatoxin concentration. Although there were carry-over effects, caution should be taken when drawing recommendations about discontinuing biocontrol use. Cost-benefit analyses of single season and carry-over influences are needed to optimize use by communities of smallholder farmers in sub-Saharan Africa.
Collapse
Affiliation(s)
- Joseph Atehnkeng
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Peter S. Ojiambo
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria,Center for Integrated Fungal Research, Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, United States
| | - Alejandro Ortega-Beltran
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Joao Augusto
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - Peter J. Cotty
- College of Food Science and Engineering, Ocean University of China, Qingdao, China,Agricultural Research Service, United States Department of Agriculture, Tucson, AZ, United States
| | - Ranajit Bandyopadhyay
- Pathology and Mycotoxin, International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria,*Correspondence: Ranajit Bandyopadhyay,
| |
Collapse
|
5
|
Mahuku G, Mauro A, Pallangyo B, Nsami E, Boni S, Koyano E, Mponda O, Ortega-Beltran A, Atehnkeng J, Aquiline F, Samuel R, Njela J, Cotty P, Bandyopadhyay R. Atoxigenic-based technology for biocontrol of aflatoxin in maize and groundnuts for Tanzania. WORLD MYCOTOXIN J 2022. [DOI: 10.3920/wmj2021.2758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Application of biocontrol products containing atoxigenic isolates of Aspergillus flavus to reduce aflatoxin content in crops is an effective strategy for managing aflatoxin in several regions throughout the world. We report the development and validation of two aflatoxin biocontrol products, Aflasafe TZ01 and Aflasafe TZ02, for use in maize and groundnut in Tanzania, a country frequently affected by aflatoxin contamination. Each product contains four atoxigenic A. flavus genotypes native and widely distributed in Tanzania. Efficacy tests on maize and groundnut were conducted over two years and in four regions of Tanzania where aflatoxin contamination is prevalent. Application of both products significantly (P<0.05) reduced aflatoxin levels in maize and groundnut in both years and in all districts. No differences were observed in total Aspergillus section Flavi population in treated and untreated fields, revealing that application of the biocontrol products do not alter overall Aspergillus populations in the environment. The results indicate that both products are effective tools for aflatoxin mitigation in groundnut and maize. The products were officially registered in 2018. Currently, there are scale-out and-up efforts of aflatoxin biocontrol products in Tanzania through a private sector company that is making the products available to farmers. Protecting maize and groundnut from aflatoxin contamination in Tanzania can result in health, income, and trade benefits.
Collapse
Affiliation(s)
- G. Mahuku
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - A. Mauro
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - B. Pallangyo
- Plant Health Services, Ministry of Agriculture, P.O. Box 2182, Dodoma, Tanzania
| | - E. Nsami
- National Biological Control Center, P.O. Box 30031, Kibaha, Tanzania
| | - S.B. Boni
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
- World Vegetable Center, Eastern and Southern Africa, P.O. Box 10, Duluti, Arusha, Tanzania
| | - E. Koyano
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - O. Mponda
- Department of Research, Ministry of Agriculture, Livestock and Fisheries, P.O. Box 9192, Dar es Salaam, Tanzania
| | - A. Ortega-Beltran
- IITA Headquarters, PMB 5320, Oyo Road, Ibadan 200001, Oyo State, Nigeria
| | - J. Atehnkeng
- IITA Headquarters, PMB 5320, Oyo Road, Ibadan 200001, Oyo State, Nigeria
| | - F. Aquiline
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - R. Samuel
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - J. Njela
- International Institute of Tropical Agriculture (IITA) Eastern Africa Hub, Plot 25, Mwenge Coca-Cola Road, Mikocheni B, P.O. Box 34441, Dar es Salaam, Tanzania
| | - P.J. Cotty
- USDA-ARS, 416 West Congress Street, Tucson, AZ 85701, USA
| | - R. Bandyopadhyay
- IITA Headquarters, PMB 5320, Oyo Road, Ibadan 200001, Oyo State, Nigeria
| |
Collapse
|
6
|
Maxwell LA, Callicott KA, Bandyopadhyay R, Mehl HL, Orbach MJ, Cotty PJ. Degradation of Aflatoxins B 1 by Atoxigenic Aspergillus flavus Biocontrol Agents. PLANT DISEASE 2021; 105:2343-2350. [PMID: 33754847 DOI: 10.1094/pdis-01-21-0066-re] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Aflatoxins are potent Aspergillus mycotoxins that contaminate food and feed, thereby impacting health and trade. Biopesticides with atoxigenic Aspergillus flavus isolates as active ingredients are used to reduce aflatoxin contamination in crops. The mechanism of aflatoxin biocontrol is primarily attributed to competitive exclusion but, sometimes, aflatoxin is reduced by greater amounts than can be explained by displacement of aflatoxin-producing fungi on the crop. Objectives of this study were to (i) evaluate the ability of atoxigenic A. flavus genotypes to degrade aflatoxin B1 (AFB1) and (ii) characterize impacts of temperature, time, and nutrient availability on AFB1 degradation by atoxigenic A. flavus. Aflatoxin-contaminated maize was inoculated with atoxigenic isolates in three separate experiments that included different atoxigenic genotypes, temperature, and time as variables. Atoxigenic genotypes varied in aflatoxin degradation but all degraded AFB1 >44% after 7 days at 30°C. The optimum temperature for AFB1 degradation was 25 to 30°C, which is similar to the optimum range for AFB1 production. In a time-course experiment, atoxigenics degraded 40% of AFB1 within 3 days, and 80% of aflatoxin was degraded by day 21. Atoxigenic isolates were able to degrade and utilize AFB1 as a sole carbon source in a chemically defined medium but quantities of AFB1 degraded declined as glucose concentrations increased. Degradation may be an additional mechanism through which atoxigenic A. flavus biocontrol products reduce aflatoxin contamination pre- or postharvest. Thus, selection of optimal atoxigenic active ingredients can include assessment of both competitive ability in agricultural fields and their ability to degrade aflatoxins.
Collapse
Affiliation(s)
- Lourena A Maxwell
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721, U.S.A
- Eduado Mondlane University, P. O. Box 257, Maputo, Mozambique
| | - Kenneth A Callicott
- United States Department of Agriculture-Agricultural Research Service, Arid-Land Agricultural Research Center, Tucson, AZ 85701, U.S.A
| | | | - Hillary L Mehl
- United States Department of Agriculture-Agricultural Research Service, Arid-Land Agricultural Research Center, Tucson, AZ 85701, U.S.A
| | - Marc J Orbach
- School of Plant Sciences, University of Arizona, Tucson, AZ 85721, U.S.A
| | - Peter J Cotty
- School of Food Science and Engineering, Ocean University of China, Qingdao, China
| |
Collapse
|
7
|
Islam M, Callicott KA, Mutegi C, Bandyopadhyay R, Cotty PJ. Distribution of active ingredients of a commercial aflatoxin biocontrol product in naturally occurring fungal communities across Kenya. Microb Biotechnol 2021; 14:1331-1342. [PMID: 33336897 PMCID: PMC8313261 DOI: 10.1111/1751-7915.13708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 11/28/2022] Open
Abstract
Human populations in Kenya are repeatedly exposed to dangerous aflatoxin levels through consumption of contaminated crops. Biocontrol with atoxigenic Aspergillus flavus is an effective method for preventing aflatoxin in crops. Although four atoxigenic A. flavus isolates (C6E, E63I, R7H and R7K) recovered from maize produced in Kenya are registered as active ingredients for a biocontrol product (Aflasafe KE01) directed at preventing contamination, natural distributions of these four genotypes prior to initiation of commercial use have not been reported. Distributions of the active ingredients of KE01 based on haplotypes at 17 SSR loci are reported. Incidences of the active ingredients and closely related haplotypes were determined in soil collected from 629 maize fields in consecutive long and short rains seasons of 2012. The four KE01 haplotypes were among the top ten most frequent. Haplotype H-1467 of active ingredient R7K was the most frequent and widespread haplotype in both seasons and was detected in the most soils (3.8%). The four KE01 haplotypes each belonged to large clonal groups containing 27-46 unique haplotypes distributed across multiple areas and in 21% of soils. Each of the KE01 haplotypes belonged to a distinct vegetative compatibility group (VCG), and all A. flavus with haplotypes matching a KE01 active ingredient belonged to the same VCG as the matching active ingredient as did all A. flavus haplotypes differing at only one SSR locus. Persistence of the KE01 active ingredients in Kenyan agroecosystems is demonstrated by detection of identical SSR haplotypes six years after initial isolation. The data provide baselines for assessing long-term influences of biocontrol applications in highly vulnerable production areas of Kenya.
Collapse
Affiliation(s)
- Md‐Sajedul Islam
- School of Plant SciencesUSDA‐ARSThe University of ArizonaTucsonAZ85721USA
| | | | - Charity Mutegi
- International Institute of Tropical AgricultureNairobiKenya
| | | | - Peter J. Cotty
- School of Plant SciencesUSDA‐ARSThe University of ArizonaTucsonAZ85721USA
- College of Food Science and EngineeringOcean University of ChinaQingdaoShandong266003China
| |
Collapse
|
8
|
Garcia-Lopez MT, Luo Y, Ortega-Beltran A, Jaime R, Moral J, Michailides TJ. Quantification of the Aflatoxin Biocontrol Strain Aspergillus flavus AF36 in Soil and in Nuts and Leaves of Pistachio by Real-Time PCR. PLANT DISEASE 2021; 105:1657-1665. [PMID: 33084543 DOI: 10.1094/pdis-05-20-1097-re] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The species Aspergillus flavus and A. parasiticus are commonly found in the soils of nut-growing areas in California. Several isolates can produce aflatoxins that occasionally contaminate nut kernels, conditioning their sale. Strain AF36 of A. flavus, which does not produce aflatoxins, is registered as a biocontrol agent for use in almond, pistachio, and fig crops in California. After application in orchards, AF36 displaces aflatoxin-producing Aspergillus spp. and thus reduces aflatoxin contamination. Vegetative compatibility assays (VCAs) have traditionally been used to track AF36 in soils and crops where it has been applied. However, VCAs are labor intensive and time consuming. Here, we developed a quantitative real-time PCR (qPCR) protocol to quantify proportions of AF36 accurately and efficiently in different substrates. Specific primers to target AF36 and toxigenic strains of A. flavus and A. parasiticus were designed based on the sequence of aflC, a gene essential for aflatoxin biosynthesis. Standard curves were generated to calculate proportions of AF36 based on threshold cycle values. Verification assays using pure DNA and conidial suspension mixtures demonstrated a significant relationship by regression analysis between known and qPCR-measured AF36 proportions in DNA (R2 = 0.974; P < 0.001) and conidia mixtures (R2 = 0.950; P < 0.001). Tests conducted by qPCR in pistachio leaves, nuts, and soil samples demonstrated the usefulness of the qPCR method to precisely quantify proportions of AF36 in diverse substrates, ensuring important time and cost savings. The outputs of this study will serve to design better aflatoxin management strategies for pistachio and other crops.
Collapse
Affiliation(s)
- M Teresa Garcia-Lopez
- Department of Agronomy (Maria de Maeztu Excellence Unit), University of Córdoba, Campus de Rabanales, 14071 Córdoba, Spain
- Department of Plant Pathology, University of California-Davis Kearney Agricultural Research and Extension Center, Parlier, CA 93648, U.S.A
| | - Yong Luo
- Department of Plant Pathology, University of California-Davis Kearney Agricultural Research and Extension Center, Parlier, CA 93648, U.S.A
| | | | - Ramon Jaime
- Department of Plant Pathology, University of California-Davis Kearney Agricultural Research and Extension Center, Parlier, CA 93648, U.S.A
| | - Juan Moral
- Department of Agronomy (Maria de Maeztu Excellence Unit), University of Córdoba, Campus de Rabanales, 14071 Córdoba, Spain
| | - Themis J Michailides
- Department of Plant Pathology, University of California-Davis Kearney Agricultural Research and Extension Center, Parlier, CA 93648, U.S.A
| |
Collapse
|
9
|
Senghor AL, Ortega-Beltran A, Atehnkeng J, Jarju P, Cotty PJ, Bandyopadhyay R. Aflasafe SN01 is the First Biocontrol Product Approved for Aflatoxin Mitigation in Two Nations, Senegal and The Gambia. PLANT DISEASE 2021; 105:1461-1473. [PMID: 33332161 DOI: 10.1094/pdis-09-20-1899-re] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Aflatoxin contamination is caused by Aspergillus flavus and closely related fungi. In The Gambia, aflatoxin contamination of groundnut and maize, two staple and economically important crops, is common. Groundnut and maize consumers are chronically exposed to aflatoxins, sometimes at alarming levels, and this has severe consequences on their health and productivity. Aflatoxin contamination also impedes commercialization in local and international premium markets. In neighboring Senegal, an aflatoxin biocontrol product containing four atoxigenic isolates of A. flavus, Aflasafe SN01, has been registered and is approved for commercial use in groundnut and maize. We detected that the four genotypes composing Aflasafe SN01 are also native to The Gambia. The biocontrol product was tested during two years in 129 maize and groundnut fields and compared with corresponding untreated fields cropped by smallholder farmers in The Gambia. Treated crops contained up to 100% less aflatoxins than untreated crops. A large portion of the crops could have been commercialized in premium markets due to the low aflatoxin content (in many cases no detectable aflatoxins), both at harvest and after storage. Substantial aflatoxin reductions were also achieved when commercially produced groundnut received treatment. Here we report for the first time the use and effectiveness of an aflatoxin biocontrol product registered for use in two nations. With the current scale-out and -up efforts of Aflasafe SN01, a large number of farmers, consumers, and traders in The Gambia and Senegal will obtain health, income, and trade benefits.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
Collapse
Affiliation(s)
- A L Senghor
- La Direction de Protection Végétaux, BP20054 Dakar, Senegal
| | - A Ortega-Beltran
- International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - J Atehnkeng
- International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| | - P Jarju
- National Food Security, Processing and Marketing Corporation, Denton Bridge, Banjul, The Gambia
| | - P J Cotty
- United States Department of Agriculture, Agricultural Research Service, Tucson, AZ 85719, U.S.A
- College of Food Science and Engineering, Ocean University of China, Qingdao, 266003, China
| | - R Bandyopadhyay
- International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
| |
Collapse
|
10
|
Predicted Aflatoxin B 1 Increase in Europe Due to Climate Change: Actions and Reactions at Global Level. Toxins (Basel) 2021; 13:toxins13040292. [PMID: 33924246 PMCID: PMC8074758 DOI: 10.3390/toxins13040292] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/16/2021] [Accepted: 04/18/2021] [Indexed: 02/07/2023] Open
Abstract
Climate change (CC) is predicted to increase the risk of aflatoxin (AF) contamination in maize, as highlighted by a project supported by EFSA in 2009. We performed a comprehensive literature search using the Scopus search engine to extract peer-reviewed studies citing this study. A total of 224 papers were identified after step I filtering (187 + 37), while step II filtering identified 25 of these papers for quantitative analysis. The unselected papers (199) were categorized as “actions” because they provided a sounding board for the expected impact of CC on AFB1 contamination, without adding new data on the topic. The remaining papers were considered as “reactions” of the scientific community because they went a step further in their data and ideas. Interesting statements taken from the “reactions” could be summarized with the following keywords: Chain and multi-actor approach, intersectoral and multidisciplinary, resilience, human and animal health, and global vision. In addition, fields meriting increased research efforts were summarized as the improvement of predictive modeling; extension to different crops and geographic areas; and the impact of CC on fungi and mycotoxin co-occurrence, both in crops and their value chains, up to consumers.
Collapse
|
11
|
Moore GG. Practical considerations will ensure the continued success of pre-harvest biocontrol using non-aflatoxigenic Aspergillus flavus strains. Crit Rev Food Sci Nutr 2021; 62:4208-4225. [PMID: 33506687 DOI: 10.1080/10408398.2021.1873731] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
There is an important reason for the accelerated use of non-aflatoxigenic Aspergillus flavus to mitigate pre-harvest aflatoxin contamination… it effectively addresses the imperative need for safer food and feed. Now that we have decades of proof of the effectiveness of A. flavus as biocontrol, it is time to improve several aspects of this strategy. If we are to continue relying heavily on this form of aflatoxin mitigation, there are considerations we must acknowledge, and actions we must take, to ensure that we are best wielding this strategy to our advantage. These include its: (1) potential to produce other mycotoxins, (2) persistence in the field in light of several ecological factors, (3) its reproductive and genetic stability, (4) the mechanism(s) employed that allow it to elicit control over aflatoxigenic strains and species of agricultural importance and (5) supplemental alternatives that increase its effectiveness. There is a need to be consistent, practical and thoughtful when it comes to implementing this method of mycotoxin mitigation since these fungi are living organisms that have been adapting, evolving and surviving on this planet for tens-of-millions of years. This document will serve as a critical review of the literature regarding pre-harvest A. flavus biocontrol and will discuss opportunities for improvements.
Collapse
Affiliation(s)
- Geromy G Moore
- United States Department of Agriculture, Agricultural Research Service, New Orleans, USA
| |
Collapse
|
12
|
Agbetiameh D, Ortega-Beltran A, Awuah RT, Atehnkeng J, Elzein A, Cotty PJ, Bandyopadhyay R. Field efficacy of two atoxigenic biocontrol products for mitigation of aflatoxin contamination in maize and groundnut in Ghana. BIOLOGICAL CONTROL : THEORY AND APPLICATIONS IN PEST MANAGEMENT 2020; 150:104351. [PMID: 33144821 PMCID: PMC7457722 DOI: 10.1016/j.biocontrol.2020.104351] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 06/13/2020] [Accepted: 06/15/2020] [Indexed: 06/11/2023]
Abstract
Biological control is one of the recommended methods for aflatoxin mitigation. Biocontrol products must be developed, and their efficacy demonstrated before widespread use. Efficacy of two aflatoxin biocontrol products, Aflasafe GH01 and Aflasafe GH02, were evaluated in 800 maize and groundnut farmers' fields during 2015 and 2016 in the Ashanti, Brong Ahafo, Northern, Upper East, and Upper West regions of Ghana. Both products were developed after an extensive examination of fungi associated with maize and groundnut in Ghana. Each product contains as active ingredient fungi four Aspergillus flavus isolates belonging to atoxigenic African Aspergillus Vegetative Compatibility Groups (AAVs) widely distributed across Ghana. An untreated field was maintained for each treated field to determine product efficacy. Proportions of atoxigenic AAVs composing each product were assessed in soils before product application, and soils and grains at harvest. Significant (P < 0.05) displacement of toxigenic fungi occurred in both crops during both years, in all five regions. Biocontrol-treated crops consistently had significantly (P < 0.05) less aflatoxins (range = 76% to 100% less; average = 99% less) than untreated crops. Results indicate that both biocontrol products are highly efficient, cost-effective, environmentally safe tools for aflatoxin mitigation. Most crops from treated fields could have been sold in both local and international food and feed premium markets. Adoption and use of biocontrol products have the potential to improve the health of Ghanaians, and both income and trade opportunities of farmers, aggregators, distributors, and traders.
Collapse
Affiliation(s)
- Daniel Agbetiameh
- International Institute of Tropical Agriculture (IITA), Ibadan 200001, Nigeria
- Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | | | - Richard T. Awuah
- Department of Crop and Soil Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | - Joseph Atehnkeng
- International Institute of Tropical Agriculture (IITA), Ibadan 200001, Nigeria
| | - Abuelgasim Elzein
- International Institute of Tropical Agriculture (IITA), Ibadan 200001, Nigeria
| | - Peter J. Cotty
- United States Department of Agriculture – Agricultural Research Service, Tucson, AZ 85721, USA
- School of Food Science and Engineering, Ocean University of China, Qingdao, China
| | | |
Collapse
|
13
|
Ortega-Beltran A, Cotty PJ. Influence of Wounding and Temperature on Resistance of Maize Landraces From Mexico to Aflatoxin Contamination. FRONTIERS IN PLANT SCIENCE 2020; 11:572264. [PMID: 33072148 PMCID: PMC7541827 DOI: 10.3389/fpls.2020.572264] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Accepted: 09/04/2020] [Indexed: 05/11/2023]
Abstract
Maize is a staple for billions across the globe. However, in tropical and sub-tropical regions, maize is frequently contaminated with aflatoxins by Aspergillus section Flavi fungi. There is an ongoing search for sources of aflatoxin resistance in maize to reduce continuous exposures of human populations to those dangerous mycotoxins. Large variability in susceptibility to aflatoxin contamination exists within maize germplasm. In Mexico, several maize landrace (MLR) accessions possess superior resistance to both Aspergillus infection and aflatoxin contamination but their mechanisms of resistance have not been reported. Influences of kernel integrity on resistance of four resistant and four susceptible MLR accessions were evaluated in laboratory assays. Wounds significantly (P < 0.05) increased susceptibility to aflatoxin contamination even when kernel viability was unaffected. Treatments supporting greater A. flavus reproduction did not (P > 0.05) proportionally support higher aflatoxin accumulation suggesting differential influences by some resistance factors between sporulation and aflatoxin biosynthesis. Physical barriers (i.e., wax and cuticle) prevented both aflatoxin accumulation and A. flavus sporulation in a highly resistant MLR accession. In addition, influence of temperature on aflatoxin contamination was evaluated in both viable and non-viable kernels of a resistant and a susceptible MLR accession, and a commercial hybrid. Both temperature and living embryo status influenced (P < 0.05) resistance to both aflatoxin accumulation and A. flavus sporulation. Lower sporulation on MLR accessions suggests their utilization would result in reduced speed of propagation and associated epidemic increases in disease both in the field and throughout storage. Results from the current study should encourage researchers across the globe to exploit the large potential that MLRs offer to breed for aflatoxin resistant maize. Furthermore, the studies provide support to the importance of resistance based on the living host and maintaining living status to reducing episodes of post-harvest contamination.
Collapse
Affiliation(s)
| | - Peter J. Cotty
- School of Plant Sciences, The University of Arizona, Tucson, AZ, United States
- Agricultural Research Service, United States Department of Agriculture, Tucson, AZ, United States
- School of Food Science and Engineering, Ocean University of China, Qingdao, China
| |
Collapse
|
14
|
Ortega‐Beltran A, Callicott KA, Cotty PJ. Founder events influence structures of Aspergillus flavus populations. Environ Microbiol 2020; 22:3522-3534. [PMID: 32515100 PMCID: PMC7496522 DOI: 10.1111/1462-2920.15122] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2019] [Revised: 04/29/2020] [Accepted: 06/04/2020] [Indexed: 12/14/2022]
Abstract
In warm regions, agricultural fields are occupied by complex Aspergillus flavus communities composed of isolates in many vegetative compatibility groups (VCGs) with varying abilities to produce highly toxic, carcinogenic aflatoxins. Aflatoxin contamination is reduced with biocontrol products that enable atoxigenic isolates from atoxigenic VCGs to dominate the population. Shifts in VCG frequencies similar to those caused by the introduction of biocontrol isolates were detected in Sonora, Mexico, where biocontrol is not currently practiced. The shifts were attributed to founder events. Although VCGs reproduce clonally, significant diversity exists within VCGs. Simple sequence repeat (SSR) fingerprinting revealed that increased frequencies of VCG YV150 involved a single haplotype. This is consistent with a founder event. Additionally, great diversity was detected among 82 YV150 isolates collected over 20 years across Mexico and the United States. Thirty-six YV150 haplotypes were separated into two populations by Structure and SplitsTree analyses. Sixty-five percent of isolates had MAT1-1 and belonged to one population. The remaining had MAT1-2 and belonged to the second population. SSR alleles varied within populations, but recombination between populations was not detected despite co-occurrence at some locations. Results suggest that YV150 isolates with opposite mating-type have either strongly restrained or lost sexual reproduction among themselves.
Collapse
Affiliation(s)
- Alejandro Ortega‐Beltran
- School of Plant SciencesUniversity of ArizonaTucsonAZ85721USA
- International Institute of Tropical AgriculturePMB 5320 Oyo Road, IbadanNigeria
| | | | - Peter J. Cotty
- USDA‐ARSTucsonAZ85721USA
- School of Food Science and EngineeringOcean University of ChinaQingdaoShandong266003China
| |
Collapse
|
15
|
Shenge KC, Adhikari BN, Akande A, Callicott KA, Atehnkeng J, Ortega-Beltran A, Kumar PL, Bandyopadhyay R, Cotty PJ. Monitoring Aspergillus flavus Genotypes in a Multi-Genotype Aflatoxin Biocontrol Product With Quantitative Pyrosequencing. Front Microbiol 2019; 10:2529. [PMID: 31803149 PMCID: PMC6872644 DOI: 10.3389/fmicb.2019.02529] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 10/21/2019] [Indexed: 11/13/2022] Open
Abstract
Aflatoxins pose significant food security and public health risks, decrease productivity and profitability of animal industries, and hamper trade. To minimize aflatoxin contamination in several crops, a biocontrol technology based on atoxigenic strains of Aspergillus flavus is commercially used in the United States and some African countries. Significant efforts are underway to popularize the use of biocontrol in Africa by various means including incentives. The purpose of this study was to develop quantitative pyrosequencing assays for rapid, simultaneous quantification of proportions of four A. flavus biocontrol genotypes within complex populations of A. flavus associated with maize crops in Nigeria to facilitate payment of farmer incentives for Aflasafe (a biocontrol product) use. Protocols were developed to confirm use of Aflasafe by small scale farmers in Nigeria. Nested PCR amplifications followed by sequence by synthesis pyrosequencing assays were required to quantify frequencies of the active ingredients and, in so doing, confirm successful use of biocontrol by participating farmers. The entire verification process could be completed in 3-4 days proving a savings over other monitoring methods in both time and costs and providing data in a time frame that could work with the commercial agriculture scheme. Quantitative pyrosequencing assays represent a reliable tool for rapid detection, quantification, and monitoring of multiple A. flavus genotypes within complex fungal communities, satisfying the requirements of the regulatory community and crop end-users that wish to determine which purchased crops were treated with the biocontrol product. Techniques developed in the current study can be modified for monitoring other crop-associated fungi.
Collapse
Affiliation(s)
- Kenneth C. Shenge
- United States Department of Agriculture, Agricultural Research Service, Tucson, AZ, United States
| | - Bishwo N. Adhikari
- United States Department of Agriculture, Agricultural Research Service, Tucson, AZ, United States
| | | | - Kenneth A. Callicott
- United States Department of Agriculture, Agricultural Research Service, Tucson, AZ, United States
| | - Joseph Atehnkeng
- International Institute of Tropical Agriculture, Ibadan, Nigeria
| | | | - P. Lava Kumar
- International Institute of Tropical Agriculture, Ibadan, Nigeria
| | | | - Peter J. Cotty
- United States Department of Agriculture, Agricultural Research Service, Tucson, AZ, United States
| |
Collapse
|
16
|
Bandyopadhyay R, Atehnkeng J, Ortega-Beltran A, Akande A, Falade TDO, Cotty PJ. "Ground-Truthing" Efficacy of Biological Control for Aflatoxin Mitigation in Farmers' Fields in Nigeria: From Field Trials to Commercial Usage, a 10-Year Study. Front Microbiol 2019; 10:2528. [PMID: 31824438 PMCID: PMC6882503 DOI: 10.3389/fmicb.2019.02528] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 10/21/2019] [Indexed: 01/09/2023] Open
Abstract
In sub-Saharan Africa (SSA), diverse fungi belonging to Aspergillus section Flavi frequently contaminate staple crops with aflatoxins. Aflatoxins negatively impact health, income, trade, food security, and development sectors. Aspergillus flavus is the most common causal agent of contamination. However, certain A. flavus genotypes do not produce aflatoxins (i.e., are atoxigenic). An aflatoxin biocontrol technology employing atoxigenic genotypes to limit crop contamination was developed in the United States. The technology was adapted and improved for use in maize and groundnut in SSA under the trademark Aflasafe. Nigeria was the first African nation for which an aflatoxin biocontrol product was developed. The current study includes tests to assess biocontrol performance across Nigeria over the past decade. The presented data on efficacy spans years in which a relatively small number of maize and groundnut fields (8-51 per year) were treated through use on circa 36,000 ha in commercially-produced maize in 2018. During the testing phase (2009-2012), fields treated during one year were not treated in the other years while during commercial usage (2013-2019), many fields were treated in multiple years. This is the first report of a large-scale, long-term efficacy study of any biocontrol product developed to date for a field crop. Most (>95%) of 213,406 tons of maize grains harvested from treated fields contained <20 ppb total aflatoxins, and a significant proportion (>90%) contained <4 ppb total aflatoxins. Grains from treated plots had preponderantly >80% less aflatoxin content than untreated crops. The frequency of the biocontrol active ingredient atoxigenic genotypes in grains from treated fields was significantly higher than in grains from control fields. A higher proportion of grains from treated fields met various aflatoxin standards compared to grains from untreated fields. Results indicate that efficacy of the biocontrol product in limiting aflatoxin contamination is stable regardless of environment and cropping system. In summary, the biocontrol technology allows farmers across Nigeria to produce safer crops for consumption and increases potential for access to premium markets that require aflatoxin-compliant crops.
Collapse
Affiliation(s)
| | - Joseph Atehnkeng
- International Institute of Tropical Agriculture, Ibadan, Nigeria
| | | | | | | | - Peter J. Cotty
- Agricultural Research Service, United States Department of Agriculture, Tucson, AZ, United States
| |
Collapse
|
17
|
Sserumaga JP, Ortega-Beltran A, Wagacha JM, Mutegi CK, Bandyopadhyay R. Aflatoxin-producing fungi associated with pre-harvest maize contamination in Uganda. Int J Food Microbiol 2019; 313:108376. [PMID: 31731141 DOI: 10.1016/j.ijfoodmicro.2019.108376] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 09/23/2019] [Accepted: 09/27/2019] [Indexed: 11/29/2022]
Abstract
Maize is an important staple crop for the majority of the population in Uganda. However, in tropical and subtropical climates, maize is frequently contaminated with aflatoxins, a group of cancer-causing and immuno-suppressive mycotoxins produced by Aspergillus section Flavi fungi. In Uganda, there is limited knowledge about the causal agents of aflatoxin contamination. The current study determined both the aflatoxin levels in pre-harvest maize across Uganda and the structures of communities of aflatoxin-producing fungi associated with the maize. A total of 256 pre-harvest maize samples were collected from 23 major maize-growing districts in eight agro-ecological zones (AEZ). Maize aflatoxin content ranged from 0 to 3760 ng/g although only around 5% for Ugandan thresholds. For EU it is about 16% of the samples contained aflatoxin concentrations above tolerance thresholds. A total of 3105 Aspergillus section Flavi isolates were recovered and these were dominated by the A. flavus L morphotype (89.4%). Densities of aflatoxin-producing fungi were negatively correlated with elevation. Farming systems and climatic conditions of the AEZ are thought to have influenced communities' structure composition. Fungi from different AEZ varied significantly in aflatoxin-producing abilities and several atoxigenic genotypes were identified. The extremely high aflatoxin concentrations detected in some of the studied regions indicate that management strategies should be urgently designed for use at the pre-harvest stage. Atoxigenic genotypes detected across Uganda could serve as aflatoxin biocontrol agents to reduce crop contamination from fields conditions and throughout the maize value chain.
Collapse
Affiliation(s)
- Julius P Sserumaga
- National Agricultural Research Organisation, National Crops Resources Research Institute, Namulonge, P. O. Box 7084, Kampala, Uganda.
| | | | - John M Wagacha
- School of Biological Sciences, University of Nairobi, P. O. Box 30197, 00100 Nairobi, Kenya
| | - Charity K Mutegi
- International Institute of Tropical Agriculture, Nairobi, Kenya.
| | | |
Collapse
|
18
|
Ortega-Beltran A, Moral J, Picot A, Puckett RD, Cotty PJ, Michailides TJ. Atoxigenic Aspergillus flavus Isolates Endemic to Almond, Fig, and Pistachio Orchards in California with Potential to Reduce Aflatoxin Contamination in these Crops. PLANT DISEASE 2019; 103:905-912. [PMID: 30807246 DOI: 10.1094/pdis-08-18-1333-re] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In California, aflatoxin contamination of almond, fig, and pistachio has become a serious problem in recent years due to long periods of drought and probably other climatic changes. The atoxigenic biocontrol product Aspergillus flavus AF36 has been registered for use to limit aflatoxin contamination of pistachio since 2012 and for use in almond and fig since 2017. New biocontrol technologies employ multiple atoxigenic genotypes because those provide greater benefits than using a single genotype. Almond, fig, and pistachio industries would benefit from a multi-strain biocontrol technology for use in these three crops. Several A. flavus vegetative compatibility groups (VCGs) associated with almond, fig, and pistachio composed exclusively of atoxigenic isolates, including the VCG to which AF36 belongs to, YV36, were previously characterized in California. Here, we report additional VCGs associated with either two or all three crops. Representative isolates of 12 atoxigenic VCGs significantly (P < 0.001) reduced (>80%) aflatoxin accumulation in almond and pistachio when challenged with highly toxigenic isolates of A. flavus and A. parasiticus under laboratory conditions. Isolates of the evaluated VCGs, including AF36, constitute valuable endemic, well-adapted, and efficient germplasm to design a multi-crop, multi-strain biocontrol strategy for use in tree crops in California. Availability of such a strategy would favor long-term atoxigenic A. flavus communities across the affected areas of California, and this would result in securing domestic and export markets for the nut crop and fig farmer industries and, most importantly, health benefits to consumers.
Collapse
Affiliation(s)
- Alejandro Ortega-Beltran
- 1 Department of Plant Pathology, University of California, Davis, and Kearney Agricultural Research and Extension Center, Parlier, CA 93648; and
| | - Juan Moral
- 1 Department of Plant Pathology, University of California, Davis, and Kearney Agricultural Research and Extension Center, Parlier, CA 93648; and
| | - Adeline Picot
- 1 Department of Plant Pathology, University of California, Davis, and Kearney Agricultural Research and Extension Center, Parlier, CA 93648; and
| | - Ryan D Puckett
- 1 Department of Plant Pathology, University of California, Davis, and Kearney Agricultural Research and Extension Center, Parlier, CA 93648; and
| | - Peter J Cotty
- 2 United States Department of Agriculture-Agricultural Research Service, School of Plant Sciences, The University of Arizona, Tucson, AZ 85721
| | - Themis J Michailides
- 1 Department of Plant Pathology, University of California, Davis, and Kearney Agricultural Research and Extension Center, Parlier, CA 93648; and
| |
Collapse
|
19
|
Islam MS, Callicott KA, Mutegi C, Bandyopadhyay R, Cotty PJ. Aspergillus flavus resident in Kenya: High genetic diversity in an ancient population primarily shaped by clonal reproduction and mutation-driven evolution. FUNGAL ECOL 2018; 35:20-33. [PMID: 30283498 PMCID: PMC6131765 DOI: 10.1016/j.funeco.2018.05.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 05/29/2018] [Accepted: 05/30/2018] [Indexed: 12/30/2022]
Abstract
Aspergillus flavus has long been considered to be an asexual species. Although a sexual stage was recently reported for this species from in vitro studies, the amount of recombination ongoing in natural populations and the genetic distance across which meiosis occurs is largely unknown. In the current study, genetic diversity, reproduction and evolution of natural A. flavus populations endemic to Kenya were examined. A total of 2744 isolates recovered from 629 maize-field soils across southern Kenya in two consecutive seasons were characterized at 17 SSR loci, revealing high genetic diversity (9-72 alleles/locus and 2140 haplotypes). Clonal reproduction and persistence of clonal lineages predominated, with many identical haplotypes occurring in multiple soil samples and both seasons. Genetic analyses predicted three distinct lineages with linkage disequilibrium and evolutionary relationships among haplotypes within each lineage suggesting mutation-driven evolution followed by clonal reproduction. Low genetic differentiation among adjacent communities reflected frequent short distance dispersal.
Collapse
Affiliation(s)
- Md-Sajedul Islam
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Kenneth A. Callicott
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| | - Charity Mutegi
- International Institute of Tropical Agriculture, Nairobi, Kenya
| | | | - Peter J. Cotty
- Agricultural Research Service, United States Department of Agriculture, School of Plant Sciences, University of Arizona, Tucson, AZ, USA
| |
Collapse
|