Linkage of Molecular Markers to Cercospora zeae‐maydisResistance in Maize

Gray leaf spot (GLS) of maize (Zea maysL.) caused by Cercospora zeae‐maydisTehon & E.Y. Daniels, can greatly reduce grain yield in conducive environments worldwide. This study was undertaken to evaluate a novel source of resistance to C. zeae‐maydisacross macroenvironments and link molecular markers to resistance loci by selective genotyping. A population of 144 F2:3progeny lines derived from a cross between resistant maize inbred VO613Y and susceptible inbred Pa405 were evaluated at Wooster, OH, USA, and Cedara Agricultural Research Institute, Department of Agriculture, KZN, Republic of South Africa (RSA), for resistance to C. zeae‐maydisThe lines were assigned to phenotypic classes (resistant, intermediate, and susceptible) on the basis of percent leaf area affected (PLAA) values across environments. F2:4progeny lines were produced by controlled self‐pollination of an individual plant within each F2:3line. F2:4lines derived from resistant and susceptible classes were evaluated at two Ohio locations. The same lines, plus a random sample of 54 F2:4lines representing the intermediate class, were evaluated at Cedara. Molecular marker data were analyzed on the basis of PLAA means of F2:4progenies by Kruskal–Wallis analysis and several markers on chromosomes 2 and 4 were deemed to be significantly associated with resistance. Additional molecular markers were added and composite interval mapping was conducted on genetic maps of those chromosomes. Quantitative trait loci (QTL) located on chromosome arms 2L and 4L together explained 40 to 47% of the phenotypic variation. A resistance gene analog probe flanked the significant interval on chromosome 4L. These intervals on chromosomes 2L and 4L were detected in all tests and we consider them to be suitable candidate QTL for marker‐assisted selection (MAS). These results indicate that VO613Y is a source of resistance with potential to be deployed effectively in both southern Africa and the U.S. Corn Belt.