Submitted to: American Phytopathology Society
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2010
Publication Date: 6/10/2010
Citation: Olarte, R.A., Horn, B.W., Monacell, J.T., Stone, E.A., Carbone, I. 2010. Inights into sexual reproduction in Aspergillus flavus from variation in experimental crosses and natural populations. Phytopathology 100:S92. Interpretive Summary: None required.
Technical Abstract: Aspergillus flavus contaminates many important crops worldwide and is the major producer of aflatoxins, which are cancer-causing secondary metabolites. Biological control is the most effective means of reducing inoculum levels of detrimental aflatoxin-producing fungal pathogens in agricultural systems; however, the long-term efficacy of such methods may face scrutiny with the recent discovery of the sexual cycle in these fungi. We crossed strains of opposite mating type in A. flavus to produce offspring, which were genetically and phenotypically analyzed to quantify gene flow and determine the heritability of aflatoxin (AF) and cyclopiazonic acid (CPA). We found that a single generation of sexual reproduction between a nonaflatoxigenic parent containing a single mutation in the aflatoxin cluster and an aflatoxigenic parent can restore aflatoxin production. The recombinant F1 progeny regained aflatoxigenicity through a crossover event within the aflatoxin gene cluster. Other F1 progeny in crosses between either a partial aflatoxin cluster strain or a strain missing the entire cluster and an aflatoxigenic parent regained toxicity via independent assortment of chromosomes. We also found that genetic exchange and recombination are associated with increased heritability of AF and CPA in progeny. These results suggest that a single round of sexual reproduction in A. flavus can generate contemporary patterns of recombination and toxin diversity.