Quantitative trait loci in sweet corn associated with partial resistance to Stewart's wilt, northern corn leaf blight, and common rust

Partial resistance to Stewart's wilt (Erwina stewartii, syn. Pantoea stewar tii), northern corn leaf blight (NCLB) (Exserohilum turcicum), and common r ust (Puccinia sorghi) was observed in an F-2;3 population developed from a cross between the inbred sweet corn lines IL731a and W6786. The objective o f this study was to identify quantitative trait loci (QTL) associated with partial resistance using restriction fragment length polymorphic markers. P henotypic data were collected for 2 years for Stewart's wilt, NCLB, and com mon rust but, due to significant family-environment interaction, analysis w as conducted individually on data from each year. In 2 years of evaluation for the three diseases, a total of 33 regions in the maize genome were asso ciated with partial resistance describing from 5.9 to 18% of the total phen otypic variability Of six regions common in both years, three were associat ed with partial resistance to Stewart's wilt (chromosomes 4;07, 5:03, and 6 :04), one was associated with NCLB (chromosome 9:05), and two were associat ed with common rust (chromosomes 2:04 and 3:04). The rust QTL on 3S mapped to within 20 cM of the rp3 locus and explained 17.7% of the phenotypic vari ability. Some of the QTL associated with partial resistance to the three di seases have been reported previously, and some are described here for the f irst time. Results suggest it may be possible to consolidate QTL from vario us elite backgrounds in a manner analogous to the pyramiding of major resis tance genes. We also report here on two QTL associated with anthocyanin pro duction on chromosomes 10:6 and 5:03 in the general location of the a2 gene .