Development of New Rootstocks for Use in Napa Valley Fanleaf Sites
Funding for this project is primarily directed at supporting a rootstock trial with BV Winery and Walsh Vineyard Management. Development of fanleaf resistant rootstocks is part of a larger project funded by the California Grape Rootstock Improvement Commission. The plot at BV is now well established and being trained up the stake and onto the cordon wires. This year will produce the first crop and the first yield and pruning weight data. We have sampled 100 of the susceptible control St. George vines for the presence of X. index to make sure the nematode is evenly distributed across the plot. All samples had clear feeding damage and had from 20 to 500 X. index per liter of soil. None of the foliar samples were GFLV positive yet, but it generally takes at least 2 years to detect GFLV once the vines are inoculated. This result gives us confidence that the site is uniformly and evenly infested with nematodes. We have found additional sources of X. index resistance in V. cinerea, V. rufotomentosa and M rotundifolia. These will be used in future crosses. A second generation of rupestris X rotundifolia (Rup X Rot) seedlings has been produced from crosses of resistant X susceptible seedlings. These should have excellent viticultural characteristics (less rotundifolia like) and maintain very high X. index resistance. We have also mapped the resistance trait in this population with AFLP DNA analysis and working towards establishing where resistance resides.