Response of Soluble Solids Accumulation, Fruitfulness, Cold Resistance, and Onset of Bud Growth to Differential Defoliation Stress at Véraison in Concord Grapevines

Abstract

Complete defoliation of Concord grapevines at véraison reduced the rate of fruit maturation, fruitfulness, primary bud hardiness, and delayed bud break in the spring. Partial defoliation reduced fruit maturation rate, but hardiness, fruitfulness and delayed spring bud break in a manner dependent on the distance between the foliated and defoliated portions of the vine. The data suggest that the ripening fruit cluster is a strong sink for leaf produced factors (photosynthate, hormones) which influence ripening. The grape bud is inferior to the fruit cluster in this regard and maximum cold resistance can be achieved only when conditions favoring soluble solids accumulation late in the growing season are maximized.