Effects of Rootstock and Scion Chilling during Rest on Resumption of Growth in Apple and Peach

Abstract

Abstract One-year-old nursery trees of ‘Starkspur Supreme Delicious’ apple (Malus domestica Borkh.) on MM 106, M 7a, and M 9 rootstocks and ‘Redhaven’ peach [Prunus persica (L.) Batsch] on Lovell and Nemaguard seedling rootstocks were subjected to all combinations of nonchilled, partly chilled, and fully chilled rootstocks and scions, followed by forcing in a greenhouse. Budbreak and new shoot growth were increased significantly in apple by increased scion and rootstock chilling with a significant interaction between treatment effects. New root growth was increased significantly by increased rootstock chilling, and decreased by scion chilling. Budbreak and new shoot growth in peach were increased significantly by increased scion chilling and decreased by rootstock chilling, also with a significant treatment interaction. Scions on M 9 apple rootstock had significantly less budbreak and new shoot growth, and M 7a had significantly more root growth over all the chilling treatments. There was no rootstock effect in the peach trees. Possible explanations are discussed for the rootstock chilling effect in apple and the differences in apple and peach responses to chilling treatments.