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Mapping Resistance Quantitative Trait Loci for Three Foliar Diseases in a Maize Recombinant Inbred Line Population—Evidence for Multiple Disease Resistance?

First author: Department of Plant Pathology, and second author: Department of Crop Science, North Carolina State University, Raleigh 27695; third author: United States Department of Agriculture–Agricultural Research Service (USDA-ARS) and Department of Crop Science, North Carolina State University; fourth author: Department of Statistics, North Carolina State University; fifth author: United States Department of Agriculture–Agricultural Research Service (USDA-ARS) and Department of Crop Science, North Carolina State University; sixth author, University of Missouri, 204 Curtis Hall, Columbia 65211; seventh author: Department of Horticulture and Crop Science, The Ohio State University–Ohio Agricultural Research and Development Center, 1680 Madison Avenue, Wooster 44691; and eighth author: USDA-ARS Plant Science Research Unit and Department of Plant Pathology, North Carolina State University.

Southern leaf blight (SLB), gray leaf spot (GLS), and northern leaf blight (NLB) are all important foliar diseases impacting maize production. The objectives of this study were to identify quantitative trait loci (QTL) for resistance to these diseases in a maize recombinant inbred line (RIL) population derived from a cross between maize lines Ki14 and B73, and to evaluate the evidence for the presence genes or loci conferring multiple disease resistance (MDR). Each disease was scored in multiple separate trials. Highly significant correlations between the resistances and the three diseases were found. The highest correlation was identified between SLB and GLS resistance (r = 0.62). Correlations between resistance to each of the diseases and time to flowering were also highly significant. Nine, eight, and six QTL were identified for SLB, GLS, and NLB resistance, respectively. QTL for all three diseases colocalized in bin 1.06, while QTL colocalizing for two of the three diseases were identified in bins 1.08 to 1.09, 2.02/2.03, 3.04/3.05, 8.05, and 10.05. QTL for time to flowering were also identified at four of these six loci (bins 1.06, 3.04/3.05, 8.05, and 10.05). No disease resistance QTL was identified at the largest-effect QTL for flowering time in bin 10.03.