This project continues rootstock evaluation for winegrape performance in a wide range of coastal and foothill production areas, and in sites which are infested with phylloxera, nematodes or both, or which have important site/soil conditions or limitations. This project includes sites in Amador, Napa, San Luis Obispo, Sonoma, Mendocino and Monterey Counties. At all sites we see significant differences in the performance of the rootstocks that will lead us toward more informed better rootstocks decisions.
Two sites in Amador County both have Zinfandel as the scion variety. These sites not only represent our on Zinfandel sites but the only ones in the granitic soils common to the Sierra Foothills. The first site is unique in that it is a non-irrigated site. We have reported data from this site since 1995. In terms of relative yield performance, we have seen that over time 1103P has distanced itself from the other rootstocks and 3309C has fallen behind. The second trial contains 14 rootstocks. The 2000 yield data followed the 7-year trend and 5BB had the greatest yield and O39-16 the least. The yield difference was driven by differences in both berries per cluster and cluster number.
At our Cabernet Sauvignon rootstock trial in Mendocino County we are able to look at the effect of the nematodes and their populations often increases over time. The highest yielding rootstock found in 2000 as well as in the multi year data was 110R with 8.6 and 13.4 kg vine-1 respectively and the lowest in 2000 and in the multi-year data was 101-14 with 1.8 and 5.8 kg vine-1 respectively. The 2000 data we present in our report will be coupled with nematode population data that will be collected this spring and another year of performance data in 2001.
In our report we present data from 5 sites where 2000 was the first or second year of data collection. These vineyards are all young and during the initial years of data collection we need to look at year-to-year data to establish developmental stability. Yield and pruning weight data in subsequent years will be used to establish developmental stability. Three sites are located in the Napa Valley. The first site is Merlot located mid-valley near the Silverado Trail, with well-drained, quite cobbly soil. This is only the second year in which we have collected data in this trial. For the two remaining Napa Valley sites, Chardonnay in the Carneros region and Cabernet Sauvignon near Calistoga, and 2000 was the first year of data collection. Data from two additional first year sites is also reported. One is a non-irrigated Pinot noir site in San Luis Obispo County that showed quite a bit of yield variability and lastly we have a Chardonnay site in Sonoma County. All of these sites represent opportunities to collect rootstock data from new varieties and/or conditions and will add significantly to our rootstock knowledge base.