WAX AND CUTIN LAYERS IN MAIZE KERNELS ASSOCIATED WITH RESISTANCE TO AFLATOXIN PRODUCTION BY ASPERGILLUS-FLAVUS

Thirteen maize hybrids and one maize population, MAS:gk, were screened for susceptibility to aflatoxin production by Aspergillus flavus. Mar ked differences in aflatoxin B1 production were detected among the mai ze genotypes tested. Most commercial hybrids consistently supported hi gh levels of aflatoxin accumulation. Aflatoxin levels did not differ b etween intact and wounded kernels of these genotypes. However, differe nt results were obtained from 4 of the 13 hybrids and the maize popula tion MAS:gk. Levels of aflatoxin accumulation in intact kernels of the se genotypes were lower than in the previous susceptible group of geno types. In addition, aflatoxin levels were higher in wounded than in in tact kernels. MAS:gk not only supported the lowest levels of aflatoxin production in intact kernels, but aflatoxin levels in endosperm-wound ed kernels also were significantly lower in MAS:gk than in wounded ker nels of all tested hybrids. Treatment with KOH to remove cutin from in tact kernels prior to inoculation with A. flavus effected substantial increases in aflatoxin accumulation in MAS:gk, but only marginal incre ases in the susceptible hybrid Pioneer 3154. Removing wax from the sur face of MAS:gk kernels greatly increased the susceptibility of this ge notype to aflatoxin accumulation. When wax removal was combined with t reatment with potassium hydroxide (KOH) or purified cutinase, aflatoxi n levels in kernels were equal to those in wounded control kernels in both genotypes. These results indicated that wax and cutin layers of m aize kernel pericarps may play a role in resistance to aflatoxin accum ulation in MAS:gk and some other genotypes. However, results suggest f urther that resistance in MAS:gk also may be due to other preformed co mpounds as well.