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Identification of Quantitative Trait Loci for Resistance to Southern Leaf Blight and Days to Anthesis in Two Maize Recombinant Inbred Line Populations

First and second authors: U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) Plant Science Research Unit and Department of Plant Pathology, North Carolina State University, Raleigh 27695-7616; third and fourth authors: Department of Biomolecular Sciences and Biotechnology, Università degli Studi di Milano, Milano, Italy; fifth author: R. F. Baker Center for Plant Breeding, Department of Agronomy, Iowa State University, Ames 50011; and sixth author: North Carolina State University, Department of Crop Science, Raleigh 27695-7620.

The genetic architecture underlying resistance in maize to southern leaf blight (SLB) caused by Cochliobolus heterostrophus race O is not well understood. The objective of this study was to identify loci contributing to SLB resistance in two recombinant inbred line populations and to compare these to SLB resistance loci in other populations. The two populations used were derived from crosses between maize inbred lines H99 and B73 (HB population--142 lines) and between B73 and B52 (BB population--186 lines). They were evaluated for SLB resistance and for days from planting to anthesis (DTA) in 2005 and 2006. Two replications arranged as randomized complete blocks were assessed in each year for each population. Entry mean heritabilities for disease resistance were high for both populations (0.876 and 0.761, respectively). Quantitative trait loci (QTL) for SLB resistance were identified in bins 3.04 (two QTL), 6.01, and 8.05 in the HB population and in bin 2.07 in the BB population. No overlap of DTA and SLB resistance QTL was observed, nor was there any phenotypic correlation between the traits. A comparison of the results of all published SLB resistance QTL studies suggested that bins 3.04 and 6.01 are ‘hotspots’ for SLB resistance QTL.