Genetic diversity in Aspergillus flavus: association with aflatoxin production and morphology

Abstract

Isolates of Aspergillus flavus belonging to at least 12 vegetative compatibility groups were characterized by aflatoxin production in vitro, morphology, and random amplified polymorphic DNAs. Aflatoxin B1 production differed significantly among vegetative compatibility groups; closely related isolates were similar intoxigenicity regardless of geographic origin. Cladistic analysis of DNA polymorphisms was consistent with vegetative compatibility data. A previously described dichotomy between S and L isolates of A. flavus based on morphology and physiology was strongly associated with both vegetative compatibility groups and DNA polymorphisms. All S isolates formed a single clade, apparently derived from the L group. Southern hybridizations of eight DNA amplification products showed that comigrating bands amplified by the same primer were always homologous within A. flavus but were not always homologous between A. flavus and closely related species. Results suggest that A. flavus is a species aggregate, that genotypes are dispersed over wide areas, and that aflatoxin production is more stable in nature than in culture. Key words: vegetative compatibility groups, random amplified polymorphic DNA, sclerotia, aflatoxin.