Effects of Shoot, Root, and Shank Chilling during Rest in Apple and Peach on Growth Resumption and Carbohydrates

Abstract

One-year-old nursery trees of ‘Redchief’ apple ( Malus × domestica Borkh.) on MM106, M9, and seedling rootstocks and ‘Redhaven’ peach [ Prunus persica (L.) Batsch.] on Lovell rootstock were subjected to root and shoot chilling treatments for 1500 and 1200 hr, respectively, followed by forcing in the greenhouse. Budbreak and new shoot and root growth were increased by chilling the apple root and shoot. In contrast, only shoot chilling increased these parameters in peach. When shanks of clonal apple rootstocks were treated as part of the shoot, statistical interaction between shoot and root chilling was eliminated when the shank was treated as part of the root. The root chilling effect was significant for both clonal and seedling apple rootstocks. Rootstock temperature (4° or 16°C) did not affect starch, soluble sugars, or sorbitol levels in scion, shank, or roots of apple and peach. Starch and soluble sugars generally decreased throughout the chilling and forcing phases, while sorbitol increased.