Inoculation techniques used to quantify aflatoxin resistance in corn

The development of Aspergillus flavus inoculation techniques has played an important part in developing corn (Zea mays L.) germplasm resistant to aflatoxin contamination. Corn genotypes evaluated for aflatoxin resistance in field studies must be artificially inoculated due to the sporadic nature of aflatoxin contamination from year to year. A number of different inoculation techniques are used by researchers in the South and Midwest. Field inoculation techniques either wound developing kernels or leave the kernels intact. Non-wounding techniques apply A. flavus conidia to exposed silks or silks inside the husks without damaging kernels. Wounding techniques deliver A. flavus conidia onto kernels that have been mechanically damaged. Inoculation techniques utilizing ear feeding insects to vector conidia have also been used in field studies. Environmental conditions such as ambient temperature and drought stress appear to have a significant impact on artificial inoculations. Laboratory evaluation techniques have been developed to confirm aflatoxin resistance identified in corn genotypes in the field. Color mutants and transformants of Aspergillus spp. have been used in field and laboratory studies to identify resistant genotypes. More efficient, less labor intensive, and less costly inoculation techniques need to be developed to aid in the production of aflatoxin resistant corn hybrids.