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

First author: 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; second author: USDA-ARS, Crop Genetics and Breeding Research Unit, University of Georgia Coastal Plain Experiment Station, 2747 Davis Rd., Tifton 31794; third, fourth, and sixth authors: North Carolina State University, Department of Crop Science, Raleigh 27695; fifth author: Pioneer Génétique, Pacé, France; and seventh author: USDA-ARS, Plant Science Research Unit and Department of Crop Science, North Carolina State University, Raleigh 27695

A recombinant inbred line population derived from a cross between the maize lines NC300 (resistant) and B104 (susceptible) was evaluated for resistance to southern leaf blight (SLB) disease caused by Cochliobolus heterostrophus race O and for days to anthesis in four environments (Clayton, NC, and Tifton, GA, in both 2004 and 2005). Entry mean and average genetic correlations between disease ratings in different environments were high (0.78 to 0.89 and 0.9, respectively) and the overall entry mean heritability for SLB resistance was 0.89. When weighted mean disease ratings were fitted to a model using multiple interval mapping, seven potential quantitative trait loci (QTL) were identified, the two strongest being on chromosomes 3 (bin 3.04) and 9 (bin 9.03--9.04). These QTL explained a combined 80% of the phenotypic variation for SLB resistance. Some time-point-specific SLB resistance QTL were also identified. There was no significant correlation between disease resistance and days to anthesis. Six putative QTL for time to anthesis were identified, none of which coincided with any SLB resistance QTL.

Additional keywords: flowering, Helminthosporium .