Field aflatoxin production by Aspergillus flavus and A. parasiticus on maize kernels

Abstract

Aspergillus flavus Link ex Fries spores are commonly used as inoculum for screening maize (Zea mays L.) genotypes for resistance to aflatoxin accumulation on grain. Occasionally, A. parasiticus Speare is also used for this purpose. However, only limited data are available on whether one species is as effective as the other for identifying aflatoxin-resistant genotypes. Our objective was to determine relative aflatoxin accumulation on kernels of maize containing the leafy (Lfy) gene in response to A. flavus and A. parasiticus. Aflatoxin production by A. flavus and A. parasiticus on grain of seven maize synthetics containing the Lfy gene, viz., A619, A632, Mo17, B73, HY, Wf9, and 914, was examined in three environments in Louisiana. Ears were doubly inoculated at 14 and 21 days after mid-silk by atomizing over external silks a 2 ml suspension containing 2.0×107 spores ml-1 of either A. flavus or A. parasiticus. All genotypes responded similarly in the three environments to both the fungal species. Aflatoxin B1 and B2 production did not differ in the three environments. The seven genotypes did not differ in levels of aflatoxin accumulation in response to either A. flavus or A. parasiticus. Aflatoxin production by A. flavus was detected in maize samples from all three environments, but aflatoxin production by A. parasiticus was found only in samples from Winnsboro, where moisture stress occurred. Mean B1 and B2 production by A. flavus from the three environments was, respectively, four and one-half times and two times more than that by A. parasiticus.