M.A. Walker, K. Lund, C. Agüero, S. Riaz, K. Fort, C. Heinitz, N. Romero
Grape rootstocks were first developed to address the phylloxera crisis during the late 1800s, and many of these rootstocks continue to be used. However, changes in the climate, water availability, pest pressure, and pest control practices require the development of new and better-adapted rootstocks. Many of the traits we need to address these issues are from Vitis species that have not been widely used in the past, either because they rooted poorly or had marginal phylloxera resistance.
The UC Davis grape rootstock breeding program has been studying phylloxera resistance for many years. Recent studies have examined the development of phylloxera strains capable of aggressive nodosity-based feeding on resistant rootstocks and the occurrence of foliar feeding strains, once rare in California. In order to better understand the origin of these strains, more than 500 leaf gall phylloxera samples were collected from 19 States along a meandering 5,000 km transect across phylloxera’s native range. Analysis of SSR data from 22 markers found that phylloxera populations primarily grouped by host.
Efforts to utilize Muscadinia rotundifolia’s exceptional pest resistance continue with an emphasis on resistance to nematodes, phylloxera and fanleaf degeneration. Large hybrid populations between various rootstocks and Vitis species × Muscadinia rotundifolia have been created. Many of these have strong resistance and some root moderately well, however no fertile progeny have been found. We are testing the breadth and durability of phylloxera resistance of a few fertile V. vinifera × M. rotundifolia hybrids in hopes of using these to introgress M. rotundifolia’s pest and disease resistance into commercial rootstocks. We are also using V. arizonica and a number of related species from the southwestern United States that possess strong resistance to Xiphinema index, Pierce’s disease, drought and salinity. These breeding efforts include developing strongly linked markers from SSR-based genetic maps to expedite traditional breeding and the physical mapping of resistance genes. Five rootstocks have been released from the program with resistance to aggressive root-knot nematode strains; X. index; these nematodes in a combined inoculum and at high soil temperature; and resistance to lesion, citrus and, in one case, ring nematode.
Walker, M.A., Lund, K., Agüero, C., Riaz, S., Fort, K., Heinitz, C. and Romero, N. 2014. BREEDING GRAPE ROOTSTOCKS FOR RESISTANCE TO PHYLLOXERA AND NEMATODES - IT'S NOT ALWAYS EASY. Acta Hort. (ISHS) 1045:89-97
fanleaf virus, phylloxera diversity, Vitis, Muscadinia, ring nematode

Acta Horticulturae