title: Identification of genetic defects in the atoxigenic biocontrol strain Aspergillus flavus K49 reveals the presence of a competitive recombinant group in field populations.
abstract: Contamination of corn, cotton, peanuts and tree nuts by aflatoxins is a severe economic burden for growers. A current biocontrol strategy is to use non-aflatoxigenic Aspergillus flavus strains to competitively exclude field toxigenic Aspergillus species. A. flavus K49 does not produce aflatoxins and cyclopiazonic acid (CPA) and is currently being tested in corn-growing fields in Mississippi. We found that its lack of production of aflatoxins and CPA resulted from single nucleotide mutations in the polyketide synthase gene and hybrid polyketide-nonribosomal peptide synthase gene, respectively. Furthermore, based on single nucleotide polymorphisms of the aflatoxin biosynthesis omtA gene and the CPA biosynthesis dmaT gene, we conclude that K49, AF36 and previously characterized TX9-8 form a biocontrol group. These isolates appear to be derived from recombinants of typical large and small sclerotial morphotype strains. This finding provides an easy way to select future biocontrol strains from the reservoir of non-aflatoxigenic populations in agricultural fields.
authors.affiliation: Southern Regional Research Center, Agricultural Research Service, US Department of Agriculture, New Orleans, LA 70124, United States. perngkuang.chang@ars.usda.gov
authors.forename: Perng-Kuang
authors.initials: PK
authors.lastname: Chang
authors.forename: Hamed K
authors.initials: HK
authors.lastname: Abbas
authors.forename: Mark A
authors.initials: MA
authors.lastname: Weaver
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Ehrlich
authors.forename: Leslie L
authors.initials: LL
authors.lastname: Scharfenstein
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Cotty
mesh_terms: D000348:Aflatoxins / Q000096:biosynthesis* / Q000235:genetics; D001231:Aspergillus flavus / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D018556:Crops, Agricultural / Q000382:microbiology; D005516:Food Microbiology; D007211:Indoles / Q000378:metabolism*; D010453:Peptide Synthases / Q000235:genetics*; D048630:Polyketide Synthases / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide
chemical_list: D000348:Aflatoxins; D007211:Indoles; D048630:Polyketide Synthases; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase; C000543:cyclopiazonic acid