Diallel Cross Analysis of Resistance to Gray Leaf Spot in Maize. H. O. GEVERS, Department of Genetics, University of Natal, P.O. Box 375, Pietermaritzburg 3200, Republic of South Africa. J. K. LAKE, Grain Crops Institute, Agricultural Research Council, and T. HOHLS, Department of Genetics, University of Natal, P.O. Box 375, Pietermaritzburg 3200, Republic of South Africa. Plant Dis. 78:379-383. Accepted for publication 23 July 1993. Copyright. 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0379.

Diallel cross analysis of resistance to gray leaf spot (caused by Cercospora zeae-maydis) in an inbred set of diverse heterotic types revealed marked differences in general and specific combining abilities. The former component was of greater relative importance in maize breeding material largely unselected for resistance to this disease, although nonadditive effects were recognized as playing a significant part in the resistance mechanism. Inbreds KO54W and SO507W, representing the F and M heterotic groups, respectively, exhibited the highest resistance and inbred SO713W (P heterotic group) the lowest resistance. Major dominant effects for resistance were associated with KO54W, which makes it particularly suitable for use in backcross recovery programs for gray leaf spot resistance.