QTL mapping for resistance to southern leaf blight in sweet corn

Abstract

To identify quantitative trait loci (QTL) associated with southern leaf blight (SLB) in sweet corn, a population consisting of 330 F2:3 families was developed from a T14 (resistant) × T4 (susceptible) cross. The genetic linkage map was constructed based on the F2 population, with 192 SSR markers covering a total map distance of 1260 cm, and an average interval length of 6.56 cm. These 330 F2:3 families were evaluated in 2009 and 2010 for SLB resistance following inoculation at the seedling stage and milk stage. Using composite interval mapping (CIM) in QTL Cartographer v.2.5, 7 QTL out of 18 total QTL were identified at the seedling stage on chromosomes 3, 4, 6 and 9, and the phenotypic variance explained by each QTL ranged from 4.02 to 35.4%. The 11 other QTL were identified at the milk stage on chromosomes 3, 4, 6, 8, 9 and 10 and accounted for 3.50 to 13.65% of the phenotypic variance. Two QTL were detected in both years; these were located on chromosome 3 and 4 in the marker intervals umc2275 to umc2008 and umc2287 to bnlg2162, respectively. One QTL, located on chromosome 3 between umc2275 and umc2008, was detected at both developmental stages. The findings in this study may provide useful information for marker-assisted selection (MAS) and with further genetic and breeding studies for maize SLB. Key words: Sweet corn, southern leaf blight (SLB), composite interval mapping (CIM), quantitative trait loci(QTL).