Molecular genetic support to optimize the breeding of fanleaf resistant rootstocks
This report presents results on Walker lab efforts to optimize the breeding of fanleaf degeneration (fanleaf) resistant rootstocks through molecular genetic methods. These efforts are two-fold: 1) to understand and utilize O39-16’s (a Muscadinia rotundifolia based rootstock) ability to induce tolerance to fanleaf virus infection in scions; and 2) to understand and utilize resistance from Vitis arizonica to the dagger nematode, Xiphinema index, which vectors grapevine fanleaf virus (GFLV) from vine to vine. We are in the process of repeating and clarifying past mapping and xylem sap analysis. We hope to have the previous work verified and corrected by Summer. The field trials we established to study xylem borne compounds with an influence on fanleaf infection will fruit well for the first time this Summer and we have renewed our efforts to determine the basis of induced tolerance. We also successfully completed a reworking of our fine-scale mapping efforts and that publication is submitted. This work will generate gene candidates for XiR1, the locus we have identified as responsible for X. index, resistance as derived from V. arizonica. This discovery will be followed with transformation experiments to confirm the resistance function of these candidate genes and allow us to use traditional breeding methods more carefully to avoid the breakdown of resistance and might lead to grape rootstocks genetically engineered with grape resistance genes.