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Comparison of Kernel Wax from Corn Genotypes Resistant or Susceptible to Aspergillus flavus

First, second, and third authors: Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803; fourth and fifth authors: U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA 70179; and sixth author: U.S. Department of Agriculture, Agricultural Research Service, Insect Biology and Population Management Research Laboratory, Tifton, GA 31793

Russin, J. S., Guo, B. Z., Tubajika, K. M., Brown, R. L., Cleveland, T. E., and Widstrom, N. W. 1997. Comparison of kernel wax from corn genotypes resistant or susceptible to Aspergillus flavus. Phytopathology 87: 529-533.Kernels of corn genotype GT-MAS: gk are resistant to Aspergillus flavus. Earlier studies showed that this resistance is due in part to kernel pericarp wax. Experiments were conducted to compare wax from GTMAS: gk kernels with that from kernels of several susceptible commercial hybrids. GT-MAS: gk had more pericarp wax than did the susceptible hybrids. Scanning electron microscopy revealed that GT-MAS: gk kernels appeared rough and showed abundant wax deposits on kernel surfaces. Susceptible kernels appeared much more smooth and lacked the abundant surface deposits observed in GT-MAS: gk. In vitro bioassays showed that kernel wax from GT-MAS: gk reduced A. flavus colony diameter by 35%. Colony diameters on a medium amended with wax from susceptible kernels did not differ from those of controls. Thin-layer chromatography and analyses of chromatograms using NIH Image software showed a distinctive composition for GT-MAS: gk kernel wax. Chromatograms of wax from GT-MAS: gk contained a peak unique to this genotype, but also lacked a peak common to all susceptible hybrids. This is the first report of specific kernel factors involved in resistance to A. flavus in corn.

Additional keywords: food safety, mycotoxin, pericarp, Zea mays.