Development of Next Generation Rootstocks for California Vineyards
The 2012 crosses focused on drought and salt resistance from newly screened highly resistant accessions of southwestern Vitis species; mapping of 101-14 x 110R; introgression of M. rotundifolia into 161-49C, and 5BB; GRN rootstock crosses with better rooting rootstocks and lower vigor; Ramsey x 1616C for mapping root architecture and salt tolerance; Freedom x St. George to allow study of virus tolerance; 101-14 x SG for virus and salt tolerance; and combining nematode and salt with GRNs and southwestern Vitis spp;
Fanleaf – We have made some progress on confirming the role of cytokinins and their precursors in O39-16’s ability to induce tolerance to fanleaf infection. We have tested a subset of the 101-14 x rotundifolia ‘Trayshed’ population for their cytokinins and there is variation. We will begin applying these potential biomarkers for fanleaf tolerance to this population and field trials. Our Xiphinema index resistance gene (XiR1) gene candidates have been transformed into the susceptible St. George and we should have results on the effect of these XiR1 candidates on preventing feeding by Summer. We have also launched a project to examine O39-16’s effect as a bionematicide. We have identified a field site at Niebaum Coppola; developing potted collections of common cover crops and weeds for X. index feeding studies; and healthy and infected O39-16 root systems to determine whether X. index can reacquire GFLV from them.
Salt and Drought Resistance – we made good progress on a root architecture x drought resistance assay, and have almost finished examining 30 rootstocks with a rhizotron to examine rooting angles and architecture, and confirmed that rooting angles from herbaceous cuttings are an effective trait and that these angles segregate in several potential mapping populations. A second generation cross involving V. berlandieri c9031 and vinifera now established to test this apparently single gene source of chloride exclusion from c9031. A subset will soon be tested and if salt exclusion varies it will be used as a mapping population. Extensive tests documentedthat relative growth rate has a large impact on salt uptake and extra controls are now included on all tests to assess relative growth rate.
Southwest Vitis and Salt Tolerance – Three collection trips were made in 2012 – the Red River of northern Texas and southern Oklahoma; the east flank of the Rockies in Colorado and New Mexico; a transect from Las Vegas to St. George Utah – with the goals of acquiring more highly chloride resistant germplasm and to complete a wide