Wax and Cutin Layers in Maize Kernels Associated with Resistance to Aflatoxin Production by Aspergillus flavus

Abstract

Thirteen maize hybrids and one maize population, MAS:gk, were screened for susceptibility to aflatoxin production by Aspergillus flavus . Marked differences in aflatoxin B₁ production were detected among the maize genotypes tested. Most commercial hybrids consistently supported high levels of aflatoxin accumulation. Aflatoxin levels did not differ between intact and wounded kernels of these genotypes. However, different results were obtained from 4 of the 13 hybrids and the maize population MAS:gk. Levels of aflatoxin accumulation in intact kernels of these genotypes were lower than in the previous susceptible group of genotypes. In addition, aflatoxin levels were higher in wounded than in intact kernels. MAS:gk not only supported the lowest levels of aflatoxin production in intact kernels, but aflatoxin levels in endosperm-wounded kernels also were significantly lower in MAS:gk than in wounded kernels of all tested hybrids. Treatment with KOH to remove cutin from intact kernels prior to inoculation with A. flavus effected substantial increases in aflatoxin accumulation in MAS:gk, but only marginal increases in the susceptible hybrid Pioneer 3154. Removing wax from the surface of MAS:gk kernels greatly increased the susceptibility of this genotype to aflatoxin accumulation. When wax removal was combined with treatment with potassium hydroxide (KOH) or purified cutinase, aflatoxin levels in kernels were equal to those in wounded control kernels in both genotypes. These results indicated that wax and cutin layers of maize kernel pericarps may play a role in resistance to aflatoxin accumulation in MAS:gk and some other genotypes. However, results suggest further that resistance in MAS:gk also may be due to other preformed compounds as well.

Keywords: food safety; mycotoxin; pericarp.