Using marker-assisted selection to introgress powdery mildew resistance genes from different Vitis resistance sources into wine grapes

This report presents results on Walker lab efforts to use molecular breeding tools to pyramid powdery mildew resistance from different genetic backgrounds into V. viniferabased cultivars. Progress has been made on a number of fronts. We have: 1) Examined several sources of powdery mildew resistance from Muscadinia rotundifolia and used these genetic markers to evaluate parents and progeny from our crosses. 2) Worked to verify the single dominant gene (locus) nature of resistance from the apparently resistant V. vinifera table grape, Kishmish vatkana, and test its reliability under California environmental conditions; 3) Utilized the above mentioned sources to make crosses that combine resistance from rotundifolia and vinifera selections; 4) Initiated the study of V. cinerea B9 based powdery mildew resistance; 5) Initiated the utilization of powdery mildew resistance from wild Chinese species in collaboration with the USDA; and 6) Investigated the origin powdery mildew resistance in vinifera-based table grape selections and using the Kishmish vatkana allelic profile have searched for other resistant selections that possess this unusual and very valuable source of powdery mildew resistance. 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. This would insure that their resistance is more durable and that it functions under a broad range of environmental conditions to provide low input, environmentally ?green? grapevines that would not require fungicides for powdery mildew.