Surya Sapkota

Date of Graduation

Summer 2013


Master of Science in Plant Science (Agriculture)


College of Agriculture

Committee Chair

Chin-Feng Hwang


Norton (Vitis aestivalis), the official grape of the State of Missouri, is grown in many U.S. regions where V. vinifera (the European grape used for most wine-making worldwide) production requires extensive pesticide use for fungal disease management. Grape growers throughout the Midwest have found that Norton is resistant to powdery mildew caused by the fungus, Erysiphe necator. The major goal of my research is to use a limited mapping strategy to identify quantitative trait locus (QTL) for powdery mildew resistance inherited from the Norton grape. In view of this, a mapping population was constructed in 2005 including 94 individuals from a cross between V. aestivalis ‘Norton' and V. vinifera ‘Cabernet Sauvignon'. This population was expanded to 244 genotypes by repeating the same cross in 2011. To date, the major loci for powdery mildew resistance from a broad range of Vitis species have been genetically mapped to chromosomes 9, 12, 13, 14, 15 and 18. I tested a total of 241 previously published simple sequence repeat (SSR) markers (V. vinifera) from these 6 chromosomes on two parents (Norton and Cabernet Sauvignon) and four of their progenies. Ninety-five of them showed polymorphism. These polymorphic markers were then further screened throughout a mapping population of 138 genotypes. A linkage map of Norton based on these 6 chromosomes was constructed. The segregation of powdery mildew resistant phenotype was also evaluated under in vitro and green house conditions. A minor (QTL) was discovered on linkage group 12 linked to the marker FAM71 with a LOD value of 2.7 that explains about 9 % of the total phenotypic variation. Further genotyping and phenotyping screening are necessary to identify additional resistance loci that are responsible for powdery mildew resistance.


Norton, genotyping, phenotyping, JoinMap, QTL

Subject Categories

Plant Sciences


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