Aspergillus flavus and Aspergillus parasiticus are closely related, morphologically similar species belonging to the Aspergillus section Flavi. Both species can produce aflatoxins, but not all strains of either species do so. Aflatoxin contamination of crops such as peanuts and corn is a worldwide problem. A possible solution is the use of nontoxigenic strains of Aspergillus as biocontrol agents to competitively exclude their toxigenic counterparts in the field. Knowledge of genetic diversity, strain identification and the potential for genetic exchange are essential for predicting the likely success of such a strategy. RAPD and microsatellite analysis of 35 Australia strains distinguished A. flavus from A. parasiticus strains. A. flavus strains were further divided into two distinct groups; Groups 1 and 2. Group 1 and 2 A. flavus strains differed in their toxin production profiles, and mode of reproduction analysis revealed evidence for recombination in Group 1 A. flavus but not in Group 2. These differences suggested that Group 2 A. flavus are a new species. A global survey of 296 strains, including strains from Africa, Asia, Oceania, Europe, North and South America, using microsatellites, revealed 271 different genotypes and that both A. flavus and A. parasiticus strains showed no correlation between genotype and geographic origin or ability to produce aflatoxin. The majority of A. flavus strains studied clustered within Group 1 A. flavus. Group 2 A. flavus were mainly restricted to the Southern Hemisphere. Implications for a biocontrol strategy are discussed.
Full conference title:
23rd Fungal Genetics Conference
- Fungal Genetics Conference 23rd (2002)