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

The overall goal of this project is to identify genetic markers for multiple sources of powdery mildew resistance and use them to combine these resistances into a single background. Combining these resistances cannot be done without genetic markers, since the phenotype (resistance to powdery mildew) is the same from each resistance source. We have made good progress at identifying and using markers to mildew resistance, but we need to understand how the marked genes work and if they are different to gain the greatest advantage in combining the resistances. To enable this improved understanding this project is being melded into a new collaborative project between my lab and that or Prof. Dario Cantu, our recently hired “omics” specialist who has had extensive experience working with disease resistance genes in wheat. Dario’s experience will greatly aid our molecular genetics effort to breed new varieties with durable mildew resistance. We have made good progress in developing and using genetic markers from two rotundifoliabased resistance sources; from the pure vinifera cultivar Karadzhandal; and from two accessions of the Chinese species V. romanetii. We are also beginning to map a new form of resistance from another Chinese species, which is taxonomically distant from V. romanetii and V. davidii and has very strong resistance. We have been mapping and using these resistance sources and have assumed that they work in different ways because the location of their resistance genes differs. Some of the genes may be copies that do the same thing but are located on different chromosomes. Dr. Cantu’s involvement in the project will allow us to better understand how the resistance works and which resistance sources are the most genetically and functionally different so that we have the greatest chance of creating lines with durable resistance from multiple genes. We have advanced resistance through backcrossing and crossing lines with different resistance markers and are now poised to begin combining as many lines with different resistance genes as possible. We have also crossed our advanced Pierce’s disease resistant selections with advanced powdery mildew resistant selections and have many selections with >90%vinifera parentage, good fruit quality and resistance to both powdery mildew and PD.