KERNEL INFECTION AND AFLATOXIN PRODUCTION IN MAIZE BY ASPERGILLUS-FLAVUS RELATIVE TO INOCULATION AND HARVEST DATES

Preharvest kernel infection by Aspergillus flavus and subsequent aflat oxin contamination of maize (Zea mays) grain is a chronic economic pro blem in the southern part of the United States. Studies were conducted to determine the time of inoculation and harvest date most effective for identifying maize genotypes resistant to kernel infection and afla toxin contamination by A. flavus. Inoculation of ears with A. flavus 6 days after midsilk resulted in as many or more infected kernels than inoculation of ears 12 and 18 days after midsilk. Multiple inoculation s did not increase incidence of kernel infection or aflatoxin contamin ation. The percentage of infected kernels in inoculated resistant and susceptible hybrids was similar at 46 and 50 days after midsilk, but t he percentage of infected kernels was greater in susceptible hybrids a t later harvest dates. Thus, resistant hybrid, differed significantly from susceptible hybrids for infection levels for harvest dates of 54- 62 days after midsilk. One susceptible hybrid had markedly higher afla toxin contamination than the other three hybrids. Selection for resist ance to A. flavus should be more effective at harvest dates around 60 days after midsilk than when grain reaches physiological maturity.