Comparison of Two Inoculation Methods for Evaluating Maize for Resistance toAspergillus flavusInfection and Aflatoxin Accumulation

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Aflatoxin, the most potent carcinogen found in nature, is produced by the fungusAspergillus flavusand occurs naturally in maize,Zea maysL. Growing maize hybrids with genetic resistance to aflatoxin contamination are generally considered a highly desirable way to reduce losses to aflatoxin. Developing resistant hybrids requires reliable inoculation methods for screening maize germplasm for resistance toA. flavusinfection and aflatoxin accumulation. The side-needle technique is a widely used inoculation technique: anA. flavusconidial suspension is injected underneath the husks into the side of the ear. This wounds the ear and limits expression of resistance associated with husk coverage, pericarp thickness, and seed coat integrity. In this investigation, the side-needle technique was compared with a second inoculation method that involved dispensing wheat kernels infected withA. flavusinto plant whorls at 35 and 49 days after planting. Results showed that although the side-needle technique produced higher levels of aflatoxin accumulation, differences inA. flavusbiomass produced by the two inoculation techniques were not significant. Both inoculation techniques were effective in differentiating resistant and susceptible single cross hybrids irrespective of the use ofA. flavusinfection or aflatoxin accumulation as a basis to define resistance.