- Develop screen for X index resistance.
- Screen rupestris x rotundifolia, champinii x rotundifolia, other rotundifolia hybrids in a lab or greenhouse assay to choose candidates for field testing.
- Continue searching for other forms of resistance to X. index and GFLV for use in fanleaf resistant rootstock breeding.
- Map X. index resistance with DNA markers (RAPD and AFLP) to locate genes responsible for resistance. Study new seedling populations (produced during the 96 season) to determine the genetic and mechanistic controls of fanleaf resistance.
- Field test X. index resistant rupestris x rotundifolia selections for their resistance to fanleaf.
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. We sampled 60 of the susceptible control St. George vines at this site in June to see how evenly X. index was spread through the field. All 60 samples had clear feeding damage and had from 20 to 400 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 ~K rotundifolia (Rup X Rot) seedlings have 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 are establishing where resistance resides.