Using Marker-Assisted Selection to Introgress Powdery Mildew Resistance Genes From Different Vitis Resistance Sources into Wine Grapes

This report presents results on the Walker lab efforts in utilizing molecular breeding tools to pyramid powdery mildew resistance from different genetic backgrounds into V. vinifera-based cultivars. In a short time period of four funding years of this project, we have made quick progress that completely relies on our experience of PD resistant winegrape breeding, in hand diverse genetic resistant material, and our ability of utilizing molecular tools developed in the lab as well as in public domain. So far we have: 1) Examined several sources of powdery mildew resistance from Muscadinia rotundifolia and evaluated parents and progeny via markers that are tightly linked to the resistance, and determined the allelic profiles of markers and alleles that are linked to the resistance for MAS; 2) Developed mapping populations with two different rotundifolia cultivars and mapped two forms of a major locus denoted as Run2.1 and Run2.2 on chromosome 18; 3) Mapped locus Ren4 from Chinese origin species V. romanetii on chromosome 18; 4) Verified the single dominant gene (locus) nature of resistance from the V. vinifera table grape, Kishmish vatkana, and tested its reliability under California environmental conditions; 5) Investigated the origin of powdery mildew resistance in vinifera-based table grape selections using the Kishmish vatkana Ren1 allelic profile, and identified five additional resistant selections that possess this unusual and very valuable vinifera-based source of powdery mildew resistance; 6) Nursery screened all vinifera-based plants that had one or both alleles of Ren1 linked markers as well as other resistant germplasm; 7) Utilized the above mentioned resistance sources to make crosses that combine resistance from rotundifolia and vinifera selections; 8) Developed a breeding population to initiate the study of V. cinerea B9 and Villard blanc base powdery mildew resistance; 9) Expanded a breeding population with powdery mildew resistance from the Chinese V. romanetii and conducted field evaluations; 10) Developed resistant lines that already range up to the 94 -97%vinifera level; 11) Initiated crosses with objective of pyramiding resistant loci into single line; 12) Made crosses to develop homozygous resistant lines for at least 3 resistant loci that could be used to develop 100%resistant progeny with 50%of elite cultivar genome; 13) established in lab leaf disk assay to understand the plant pathogen interaction as well as to screen populations; 14) And finally, we are evaluating these breeding populations for fruit quality traits and disease resistance constantly each year. The knowledge and results gained from this work will lead to the development of wine and table grape selections with multiple powdery mildew resistance genes pyramided into a single line, and environmentally ?green? grapevines that do not require the application of fungicides to control powdery mildew.