Plant & Animal Genome V Conference
Town & Country Hotel, San Diego, CA, January 12-16, 1997.
PAG-V: P226 - MAPPING QTL ASSOCIATED WITH SCLEROTINIA STEM ROT IN SOYBEANS USING RAPD MARKERS
P226
MAPPING QTL ASSOCIATED WITH SCLEROTINIA STEM ROT IN SOYBEANS USING RAPD MARKERS
DELANEY, DONNA ELLEN(1), George L. Graef(1), Susan Rutledge(2), Chris Powers(2), James R. Steadman(2), Brian Diers(3)
1. Dept. of Agronomy, 279 Plant Science, University of Nebraska, Lincoln, NE 68583-0915
2. Dept. of Plant Pathology, University of Nebraska, Lincoln, NE 68583
3. Dept. of crop and Soil Sciences, Michigan State University, East Lansing, MI 48824
Sclerotinia sclerotiorum is the causal organism of sclerotinia stem rot (white mold) in soybean. The wide host range of 400 dicotyledenous species and long-term survival of this pathogen in the soil assures outbreaks of disease under favorable environments. Since disease management options are limited, resistance, thus far unidentified in soybeans, is the most cost-effective and long-term management strategy. The objective of this study was to differentiate susceptible and resistant soybean genotypes, and identify putative QTL for resistance using polymorphic RAPD markers. A leaf test, refined at the University of Nebraska for soybeans, is consistently effective in differentiating the most susceptible and the most resistant soybean lines. The laboratory leaf assay is highly correlated with the ranking of disease severity index (DSI) in replicated field trials, is non-destructive and can be used to screen segregating populations. Soybean genotypes that differ in their reaction to the pathogen were identified based on the leaf assay and field results. Williams 82, a susceptible cultivar, and five other cultivars with varying degrees of resistance, were selected as parents used to construct several breeding populations. The six cultivars were screened with 1,000 RAPD primers to identify polymorphisms between Williams 82 and the five more resistant genotypes. The polymorphism ranges from 22% for DSR-173 to 28% for Corsoy 79. A mapping population of 66 F2 plants from the Williams 82 X Corsoy 79 cross was analyzed for both disease severity and RAPD markers to identify putative QTL for resistance to sclerotinia stem rot. Of the 278 possible polymorphic primers, 220 proved to be good markers. Of those, 185 markers were placed on 29 linkage groups covering 776.5cM. One putative QTL was identified on linkage group 6 which explains 18% of the variation in lesion size.