Issue link: http://read.dmtmag.com/i/71703
Now's The Time To Sample! "There just weren't a lot of differences in the wines." —Jim Harbertson were mislabeled and not what they were supposed to be. The drought-tolerant rootstock was one of the mislabeled casualties. He noted that the experiment confirmed what many growers and winemakers already know—variety, vineyard location, and vintage are the dominating factors of grape and wine quality. Overall, he found that the scion effects and differences caused by yearly climate variation far outweighed any dif- ferences on account of rootstock. "The rootstocks had only minor effects on fruit ripening and did not consis- tently alter soluble solids, titratable acidity, potassium, or anthocyanin pigments, but the pH was higher in fruit from own-rooted vines compared with grafted Merlot and Chardonnay," he stated in his research abstract. Harbertson reported that rootstock caused few signif- icant differences in fruit and wine composition. Rather, the dominant factors were scion and, to a lesser extent, vintage. Rootstock had no effect on grape anthocyanins and tannins. However, significant but small and variable effects were observed for wine anthocyanins and tannins. He found that wines from own-rooted vines tended to have somewhat higher pH, potassium, and total tannin than did wines from grafted vines, an observation counter to other research that has found higher potas- sium in wines from grafted vines. Both Keller's and Harbertson's research findings were published in the March issue of the American Journal of Enology and Viticulture. Own roots Washington grape growers are some of the few in the world who can grow wine grapes on their own roots and not be forced to use phylloxera-resistant rootstocks. The tiny pest, which feeds on the roots of vines, reducing yields and weakening the plants, has been found in a few vineyards in the state, but the isolated infestations have been monitored for years and have not spread, perhaps due to soil or climate conditions. However, western Wash- ington vineyardists are beginning to experiment with early fruit-maturing rootstocks, and several growers in Walla Walla are interested in planting small rootstock trials. "For the most part, we've stayed away from root- stocks," said Keller, "and there's no big reason for us to switch." When cold temperatures occasionally cause winter injury to eastern Washington vineyards—like the 2010 Thanksgiving freeze—own-rooted vines that are dam- aged can be retrained from the ground and back in pro- duction the following year. The same cold damage to a grafted vineyard requires replanting the vine or regrafting in the field, a somewhat dicey option in Washington because it has yielded inconsistent results. Another bonus of own-rooted vines is cost—they are cheaper in cost than grafted vines that are more expensive for nurseries to produce. But use of rootstocks in Washington could change in the future. Keller thinks nematodes, not phylloxera, will probably force Washington growers to adopt rootstocks in the future. "Nematodes will likely be more of an issue as vine- yards go through second and third generations," he said, adding that the wine grape industry is still very young in many locations in the state, with some areas just being planted for the first time. But as vineyards get planted a second and third time, he fears nematodes will be a growing problem, and nematode-resistant rootstocks may be necessary. • www.goodfruit.com GOOD FRUIT GROWER JULY 2012 33 •Tree structure responding to optimal or stressed conditions Leaf Analysis shows •Nutrient uptake relative to healthy/ damaged cambium •Fruit mineral accumulation levels •Potential for storage disorders •Data for optimum storage segregation •Relationship to carbohydrate supply Fruit Analysis shows 509-662-1888 509-452-7707 Wenatchee, WA 98801 Union Gap, WA 9890 800-545-4206 www.cascadeanalytical.com