Genetics of Resistance to Field Kernel Infection by Aspergillus flavus in Maize

Abstract

To solve the chronic problem of maize (Zea mays L.) kernel infection by Aspergillus flavus in the southeastern USA, genetic resistance to A. flavus is needed. A 2-yr study of a diallel cross of five parents containing the leafy gene (Lfy) was conducted to evaluate the inhertance of resistance to A. flavus during 2003 and 2004. The maize percent kernel infection (PKI) rates were determined via the media-free and kernel-isolated incubation method. Highly significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were found. Parents 914 and A619 had desirable (negative) GCA effects to enhance the average performance of A. flavus resistance in hybrid progeny. The crosses 914 X A632, 914 X Wf9, and Hy X Wf9 had consistently negative SCA effects across years. The reciprocal effects were detected, indicating the presence of maternal effects in the maize kernel and the importance of direction of a cross. For example, A632 X Hy had the largest positive significant reciprocal effect; the reversal of this cross, i.e., Hy X A632, should impart resistance to progeny. A North Carolina Design-II analysis of four female lines (914, A632, HY, and Wf9) crossed with three male lines (A619, B73, and Mol7), was used to estimate additive and dominance genetic variances. Narrow-sense heritability for PKI was 37.6% and broad-sense heritability estimate was 89.1%. Breeding procedures to handle both additive and dominance variances would need to be used to improve resistance to PKI.