Field Evaluation of Wine Grape Rootstocks
Napa 4 was lost when the plot was night machine-harvested in error. Napa 5 was determined to be too immature to yield acceptable data in 1999. A revised Final Report will be submitted when the additional data is available. Amador 1. Fox Creek. The 1999 data slightly favored putative drought resistant rootstock 1103P over the rootstock 3309C more so than the long term average (1995-1999, Table 3b). However, none of the yield components individually were significantly different enough to account for the observed yields. Thus the site variability which has manifested itself in this trial before continues to show. Amador 2. Sutter Home. Yields in 1999 were about at the long term average, 1994-1999. The 1999 data followed the 6-year trend with 5BB having the greatest yield and 039-16 and 101-14 having the least. There were differences in cluster number, berries per cluster and berry wt contributing to the yield differences. Napa 3. Duckhorn Vineyards. This is a new trial near the Silverado Trail, mid-valley with well-drained, quite cobbly soil. The 1999 data (Table 4) show that 3309C is out-yielding other rootstocks by 0.5 to 1.3 kg per vine. Napa 4. Oakville Experimental Vineyard. Teleki 5C, 225 Ruggeri and 1103P lead the yield column while S04 and Kober 125AA are among the lowest yielding. Berries per cluster and berry wt are the yield components playing the most important role, although the component clusters per shoot also is involved. Shoot wt (relating to shoot length) is dramatically different varying from a low of 35 g (S04) to 110 g (1103P), resulting in dramatic differences in pruning wt, from a low of 1.4 kg/vine (101-14Mgt) to a high of almost 4.0 (1103P).