The Role of Single and Mixed Infections of Grapevine Leafroll Associated Virus-2

The first year of this project has been successful in establishing field trials that will enable us to determine susceptibility of rootstock and scion varieties to virus-induced rootstock decline (VTRD); and to correlate virus status with biological effects seen in vineyards. Approximately 2 acres have been planted with 3000 plants that were chip bud inoculated by hand with virus for 11 randomized experiments. In the first set of trials, 7 rootstocks and two scion varieties were inoculated by chipbudding with 6 virus treatments. Freedom was inoculated as a positive control for the VTRD effect. Nine grape varieties – AXR, St. George, Harmony, 101-14 Mgt, S04, Kober 5BB and 11 OR, Cabernet Franc and Chardonnay were inoculated with six virus treatments each. They were planted in a randomized complete block design (RCBD) with 5 blocks and 8 plants/treatment/block for an overall total of 2160 plants. Bud take and baseline data was taken. In the second set of trials, Freedom and Kober 5BB rootstocks (both susceptible to VTRD) were inoculated with single virus infections and artificial mixes of the single infections to assess the effects of single versus multiple virus infections on growth. They were planted in the field in an RCBD with 5 blocks and 8 plants/treatment/block for a total of 880 plants. Bud take and baseline data was taken. Extensive PCR testing for 15 grapevine viruses has been done on a selection of virus sources to further identify and characterize naturally-occurring sources of multiple and single virus infections.