Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2010
Publication Date: 4/16/2011
Citation: Riaz, S., Tenscher, A., Ramming, D.W., Walker, A. 2011. Using a limited mapping strategy to identify major QTL’s for resistance to grapevine powdery mildew (Erysiphe necator) and their use in marker-assisted breeding.. Theoretical and Applied Genetics. 122(6):1059-1073. Interpretive Summary: Powdery mildew is the most important fungal disease of grapes worldwide. In 2008, 10.2 million pounds of sulfur were applied to table and raisin grapes in California. Powdery mildew has developed resistance to a number of other chemicals used for control. The development of table and raisin grapes resistant to powdery mildew would be a great advantage to growers. The use of mildew resistant cultivars would reduce production costs and the amount of pesticides released in the atmosphere. Resistance to powdery mildew infection is found in a number of grapes species. Molecular markers were developed to identify powdery mildew resistance genes on chromosome 18 from three different sources of resistance. These markers allow breeders to select resistant table and raisin grapes that have all three sources of resistance in one plant. Multiple resistance genes will be more durable and superior to grapes with only one source of resistance. The findings have potential to eliminate chemical control of powdery mildew in the vineyard.
Technical Abstract: A limited genetic mapping strategy was used to develop genetic markers in populations segregating for powdery mildew (Erysiphe necator) resistance. A genetic map was constructed and QTL analysis completed on a population derived from Muscadinia rotundifolia cv. Magnolia. In two additional populations only markers from chromosome 13 and 18 were mapped. Significant QTLs for powdery mildew resistance were identified on chromosome 18, which distinguishes this resistance from M. rotundifolia-based Run1 resistance on chromosome 12. A population, derived from M. rotundifolia cv. Trayshed, was mapped. A locus accounting for 50% of the phenotypic variation mapped to chromosome 18 and was named Run2. The Run2 locus overlapped the region found in Magnolia-based populations, but allele sizes of flanking markers were different. Trayshed and Magnolia shared at least one allele for 68% of tested markers, but alleles of the other 32% of markers were not shared indicating the two M. rotundifolia selections were different. A major powdery mildew resistance locus termed Ren2 on chromosome 18 was discovered in a population from Vitis romanetii. Genetic mapping explained 70% of phenotypic variation in the same region of chromosome 18 found in the M. rotundifolia populations. Powdery mildew resistance genes from different backgrounds reside on chromosome 18, and genetic markers can be used to pyramid these powdery mildew resistance loci into a single line.