ASSOCIATION OF MORPHOLOGY AND MYCOTOXIN PRODUCTION WITH VEGETATIVE COMPATIBILITY GROUPS IN ASPERGILLUS-FLAVUS, ASPERGILLUS-PARASITICUS, ANDASPERGILLUS-TAMARII

Vegetative compatibility groups within populations of Aspergillus flav us, A. parasiticus, and A. tamarii from soil and peanut seeds in a pea nut field were examined for differences in morphology (colony color an d sclerotium characters) and mycotoxin production (aflatoxins, cyclopi azonic acid, and kojic acid). Aspergillus tamarii was divided into typ es A and B based on morphological differences and the lack of vegetati ve compatibility between the two types. Using digital color image proc essing, the four taxa were easily distinguished by colony color throug h analyses of peak color intensities for red, green, and blue. Color c omparisons of A. flavus vegetative compatibility groups were not possi ble because of poor sporulation by many of the isolates. Vegetative co mpatibility group 1 of A. parasiticus differed significantly from grou ps 2-9 in colony color, and groups 1-3 of A. tamarii type A and groups 1-3 of A. tamarii type B were also significantly different within eac h type. Color image processing of filtered conidia indicated that the color difference of A. parasiticus group 1 was due primarily to the fl occulose texture of the colony whereas group differences in A. tamarii types A and B were the result of conidium pigmentation. Aspergillus f lavus and A. pnrasiticzcs showed significant differences among groups in number of sclerotia, sclerotium volume, and sclerotium shape (lengt h/width ratio). Isolates of A. tamarii type B often produced irregular ly shaped sclerotia; type A isolates were nonsclerotial. Among the 11 groups of A. flavus, significant differences were detected in total af latoxin (aflatoxins B-1 + B-2), cyclopiazonic acid, and kojic acid. As pergillus parasiticus groups also showed significant differences in to tal aflatoxin (aflatoxins B-1 + B-2 + G(1) + G(2)), ratio of G(1) + G( 2)/B-1 + B-2, and kojic acid; cyclopiazonic acid was not produced by A . parasiticus. Nonaflatoxigenic isolates of A. flavus and A. parasitic us were restricted to certain groups and in A. parasiticus, all nonafl atoxigenic isolates accumulated O-methylsterigmatocystin, an immediate precursor of aflatoxin B-1. Isolates of A. tamarii type A produced cy clopiazonic acid and kojic acid whereas those of type B produced only kojic acid at concentrations six-fold higher than type A; fe tv differ ences in mycotoxin production were detected among groups in the two ty pes of A. tamarii. The high proportion of variation among isolates acc ounted for by vegetative compatibility groups suggests that isolates w ithin groups are closely related.