Location: Grape Genetics Research Unit (GGRU)Title: Construction of a high-density linkage map and QTL detection of downy mildew resistance in Vitis aestivalis-derived ‘Norton’
|SAPTOKA, SURYA - Missouri State University|
|CHEN, LI-LING - Missouri State University|
|YANG, SHANSHAN - Arizona State University|
|HYMA, KATIE - Cornell University - New York|
|HWANG, CHIN-FENG - Missouri State University|
Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2018
Publication Date: 10/19/2018
Citation: Saptoka, S., Chen, L., Yang, S., Hyma, K.E., Cadle Davidson, L.E., Hwang, C. 2018. Construction of a high-density linkage map and QTL detection of downy mildew resistance in Vitis aestivalis-derived ‘Norton’. Theoretical and Applied Genetics. 132:137-147.
Interpretive Summary: Grapevine downy mildew is a widespread and destructive disease, particularly in humid grape growing regions. Traditional grape varieties are susceptible to downy mildew, but several North American and Asian varieties have some resistance to downy mildew. To describe the genetics of downy mildew resistance in the North American grape variety ‘Norton,’ a family of grapevines was made by pollinating ‘Norton’ with the susceptible variety ‘Cabernet Sauvignon.’ Then, downy mildew disease progression was studied in this family for two years under both laboratory and field conditions. The results were similar in both years, regardless of being studied in laboratory or field. To identify the genetic region responsible for resistance, a high-resolution genetic map was made by combining two DNA marker technologies: 407 simple sequence repeat (SSR) markers and 1,665 single nucleotide polymorphism (SNP) markers. On chromosome 18, genetic analysis identified a region explaining 33.8% of the variation observed in downy mildew severity. We named this new resistance region Rpv22. DNA markers closely linked with Rpv22 resistance can be used for development of new varieties with resistance to downy mildew.
Technical Abstract: Grapevine downy mildew caused by the oomycete Plasmopara viticola is one of the most widespread and destructive diseases, particularly in humid viticultural areas where it damages green tissues and defoliates vines. Traditional Vitis vinifera wine grape cultivars are susceptible to downy mildew whereas several North American and Asian cultivars possess various levels of resistance to this disease. To identify genetic determinants of downy mildew resistance in V. aestivalis-derived ‘Norton’, a mapping population with 182 genotypes was developed from a cross between ‘Norton’ and V. vinifera ‘Cabernet Sauvignon’ from which a consensus map was constructed via 411 simple sequence repeat (SSR) markers. Using genotyping-by-sequencing, 3,825 single nucleotide polymorphism (SNP) markers were also generated. Of these, 1,665 SNP and 407 SSR markers were clustered into 19 linkage groups in 159 genotypes, spanning a genetic distance of 2,203.5 cM. Disease progression in response to P. viticola was studied in this population for two years under both laboratory and field conditions, and strong correlations were observed among data sets (Spearman correlation coefficient = 0.57 to 0.79). A quantitative trait loci (QTL) analysis indicated a resistance locus on chromosome 18, here named Rpv22, explaining 33.8% of the total phenotypic variation. Flanking markers closely linked with the trait can be further used for marker-assisted selection in the development of new cultivars with resistance to downy mildew.