Effects of Several Nematode-Resistant Rootstocks on Vine Vigor, Crop Level, and Nutrition with the Grape Variety, Grenache

Abstract

A regulated level of pruning, in which the number of fruiting units retained is balanced with the past vegetative growth of the vine, did not entirely overcome the low-yielding tendencies of very vigorous grafted vines. Fruiting efficiency of the individual spur, based on the ratio of prunings to fruit produced, was markedly lower from vines on the very vigorous stock, Dogridge, and highest on the own-rooted Grenache vines. Over the six-year period that harvest records were obtained, the heaviest-yielding vines and those showing the best balance between growth and fruit production were on the <i>V. Champini</i> selection, Salt Creek. Total carbohydrate content was markedly increased and total nitrogen level decreased in the shoots by girdling during bloom. Only the yields of the vigorous vines on Dogridge were increased by this treatment. Topping the vine at bloom did not change carbohydrate levels in the shoots at the time of berry shatter, but gave some reduction in vine vigor. A growth retardant, maleic hydrazide, used at 500 ppm as a foliar spray during bloom, was not effective in changing nutrient levels in the shoots. However, evident leaf symptoms and reduction in shoot elongation was noted late in the growing season.