AN INOCULATION DEVICE TO EVALUATE MAIZE FOR RESISTANCE TO EAR ROT AND AFLATOXIN PRODUCTION BY ASPERGILLUS-FLAVUS

Fifteen commercially available maize hybrids were evaluated for variation in susceptibility to Aspergillus flavus and aflatoxin production using an inoculation technique that wounds kernels and injects a suspension of A. flavus conidia under the husk. The inoculator consists of seven rows of 23 pins mounted in an aluminum bar, with 0.8 cm of the point ends exposed. Located in the center of the pins is a larger needle through which a spore suspension is injected under the husk. The inoculator is mounted at the end of a spray gun which is attached to a backpack sprayer. The inoculator is aligned with the ear axis, the pins are forced through the husk into kernels, and inoculum is injected under the husk. Hybrid rank for ear rot was significantly correlated between inoculations done in 1990 and 1991. Aflatoxin values, however, were not significantly correlated between years. All 15 hybrids were considered moderately to highly susceptible to A. flavus ear rot and aflatoxin accumulation. The inoculating device allows for more rapid evaluation of resistance to A. flavus ear rot than do some previous techniques. A time-of-inoculation study conducted in 1991 indicated that inoculations at 17, 20, and 23 days after midsilk result in the severest ear rot.