Identification of Chemical Components of Corn Kernel Pericarp Wax Associated with Resistance to Aspergillus flavus Infection and Aflatoxin Production

Kernel pericarp wax of the corn breeding population GT-MAS:gk has been associated with resistance to Aspergillus flavus infection and aflatoxin production. GT-MAS:gk wax, previously compared to waxes of three susceptible genotypes, was presently compared to wax of a different, and more numerous, group of susceptible lines. Wax separation by TLC confirmed previous findings, demonstrating a unique GT-MAS:gk band and a unique “susceptible” band. Only GT-MAS:gk wax inhibited the growth of A. flavus; however, no association was established, as before, between kernel wax abundance and resistance. Gas chromatography−mass spectroscopy (GC−MS) analysis of kernel whole wax showed a higher percentage of phenol-like compounds in wax from GT-MAS:gk than in waxes from the susceptible lines. The GT-MAS:gk unique band contained phenol-like compounds and ethyl-hexadecanoate; butyl-hexadecanoate was preeminent in most of the “susceptible bands”. Alkylresorcinol (phenolic compounds) content was dramatically higher in GT-MAS:gk wax than in the wax of susceptible lines. An alkylresorcinol, 5-methylresorcinol, also inhibited in vitro growth of A. flavus. These and other phenolic compounds may contribute to kernel wax inhibition of A. flavus infection/aflatoxin production. Further investigation is needed to confirm a role for them in GT-MAS:gk resistance. Keywords: mycotoxin; host resistance; Zea mays; wax