Aspergillus flavus infection and aflatoxin accumulation in resistant and susceptible maize hybrids

Field studies were conducted for 2 years in Mississippi to monitor maize kernel infection and aflatoxin accumulation caused by Aspergillus flavus at various times during the growing season. Hybrids resistant and susceptible to A. flavus were compared to determine temporal differences in infection and aflatoxin levels. The resistant hybrids tested were Mo18W x Mp313E, Mp420 x Tx601, and SC54 x SC76; and the susceptible hybrids tested were GA209 x Mp339, Mp307 x Mp428, and Mp68:616 x SC212M. The top ear of each plant was inoculated with a suspension containing A. flavus conidia at 7 days after midsilk (50% of the plants in a plot had silks emerged) using the side needle technique. Inoculated ears were harvested 35, 42, 49, 56, and 63 days after midsilk to determine kernel infection by A. flavus and aflatoxin contamination. Differences in aflatoxin levels between resistant and susceptible hybrids occurred in all harvest dates. However, significant differences between resistant and susceptible hybrids for kernel infection were not observed until 42 days after midsilk. Differences between resistant and susceptible hybrids occurred for kernel infection and aflatoxin concentrations 49, 56, and 63 days after midsilk. Incidence of kernel infection (8.1% for GA209 x Mp339) was the highest 49 days after midsilk, and aflatoxin concentrations (510 ng/g for Mp307 x Mp428) were the highest 63 days after midsilk. Maximum differences between resistant and susceptible hybrids for aflatoxin levels were observed 63 days after midsilk. Two of the resistant hybrids, Mo18W x Mp313E and Mp420 x Tx601, had significantly less aflatoxin than the three susceptible hybrids 63 days after midsilk.