Segregation for Resistance to Aflatoxin Contamination among Seeds on an Ear of Hybrid Maize1

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Abstract
Consistent differences among maize (Zea mays L.) genotypes for resistance to Aspergillus flavus Link ex Ft. infection and aflatoxin contamination have been difficult to demonstrate. Populations derived from visibly classified segregating kernels, obtained from a single fungus‐infected hybrid ear, were tested for aflatoxin contamination amounts. The objectives were to look for hypothesized differences in contamination between the two selected populations derived from kernels related no less closely than half sibs, and to determine if the differences between these two populations were consistent when samples were inoculated with A. flavus in the field and laboratory. The population (MAS:gk), expected to be resistant based on the fungus‐free appearance of kernels selected from the original ear, had significantly less aflatoxin contamination than its counterpart (MAS:pw,nf) in three of four field experiments and two of three laboratory experiments. The seven replicated experiments were conducted during a 5‐yr period, and contamination of MAS:pw,nf exceeded that of MAS:gk in all seven trials. The probability of this occurring as hypothesized, when two populations are in fact equal in resistance, is <0.01. The variation in kernel phenotype on which the initial selections were made has since disappeared, and the populations resulting from sib‐poilination do not differ in their resistance to insects nor in several other traits measured thus far. The populations MAS:gk and MAS:pw,nf offer a unique opportunity for genetic improvement for resistance to aflatoxin through selection and for investigating the mechanisms of resistance.