Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2015
Publication Date: 6/19/2015
Citation: Grubisha, L.C., Cotty, P.J. 2015. Genetic analysis of the Aspergillus flavus vegetative compatibility group to which a biological control agent that limits aflatoxin contamination in U.S. crops belongs. Applied and Environmental Microbiology. 81(17):5889-5899. doi: 10.1128/AEM.00738-15.
Interpretive Summary: Aflatoxin is a carcinogenic fungal metabolite produced by members of Aspergillus section Flavi. Aspergillus flavus is a pathogen of animals and plants and is the primary cause of aflatoxin contamination of crops. Contamination of important agricultural crops results in tremendous economic loss and human disease and even death. The most effective way of reducing aflatoxin contamination of crops is through competitive exclusion of aflatoxin-producing fungi with nonaflatoxin-producing fungi. Presently there are two genetically distinct fungi used as biopesticides for preventing contamination in the USA. Understanding the population biology of these fungi is important for developing a longterm and successful biological control program. Isolates of one of these biocontrol fungi (AF36) was collected over 16 years from five states. Population genetic analyses were conducted on this collection using several types of DNA markers. This is the first time the long-term stability of one of these biocontrol fungi has been studied. These results suggest that the biocontrol fungus AF36 is stable and highly adapted. There was no evidence of sexual recombination with aflatoxin-producing fungi. The results from this work are important for designing long-term plans for managing aflatoxin contamination of crops with biocontrol fungi and suggest biocontrol can be designed to be of long-term stable benefit.
Technical Abstract: The most effective means of reducing aflatoxin contamination of agricultural crops is through competitive exclusion of aflatoxin-producing fungi using vegetative compatibility groups (VCGs) of Aspergillus flavus that do not produce aflatoxin. Presently there are two VCGs in the USA registered with the EPA for this purpose. This study is the first population genetic study of one of these fungi. We examined VCG YV36 to which the biocontrol fungus AF36 belongs for genetic variation, reproductive mode, and presence of the SNP in the pksA gene that confers the status of nonaflatoxin-producer. Isolates in VCG YV36 used in the current study were collected from 1988 through 2005 from across the southern USA from Arizona to Georgia. Twenty-one microsatellite loci revealed one dominant haplotype over space and time. There was no evidence of recombination with aflatoxin-producing VCGs as all YV36 isolates retained the pksA SNP over the 16 years and all geographic locations, including fields treated with YV36. All YV36 isolates had the MAT1-2 mating-type locus. These results are important for understanding the biology of YV36 and for continued use of nonaflatoxin-producing VCGs in biological control.