ROOTSTOCK AND TRAINING SYSTEM AFFECT DRY-MATTER AND CARBOHYDRATE DISTRIBUTION IN GOLDEN DELICIOUS APPLE-TREES

A study was conducted to quantify the effects of rootstock and trainin g system on C allocation in apple. Dry-matter distribution was determi ned at harvest in 5-year-old 'Golden Delicious' apple (Malus domestica Borkh.) trees on four rootstocks (MM.111 EMLA,M.7a, M.26 EMLA, and M. 9 EMLA) and in three training systems (three-wire palmette, free-stand ing central leader, and nonpruned). Mobilizable carbohydrate content w as determined at harvest and leaf fall in trees from the same planting on MM.111 EMLA and M.9 EMLA in all three training systems. Training s ystem effects interacted with rootstock effects in dry weights of bran ches and of fruit. Nonpruned system shoot and fruit dry weights reflec ted known rootstock vigor; whereas, pruned system (three-wire and cent ral leader) shoot dry weights were greatest and fruit dry weights were lowest in trees on M.7a. Rootstock affected the partitioning of dry m atter between above- and below-ground tree components, with MM.111 EML A accumulating significantly more dry matter in the root system than t rees on the other rootstocks. Trees in the central leader and the thre e-wire palmette systems partitioned more dry weight into nonbearing 1- year shoots than trees in the nonpruned system. Root starch content at harvest was greater in trees on MM.111 EMLA than on M.9 EMLA, and roo t sucrose and sorbitol were less in trees on MM.111 EMLA compared to M .9 EMLA. At leaf fall, starch in young roots was equal in trees on bot h rootstocks, and sorbitol again was lower in trees on MM.111 EMLA. Ha rvest starch content of roots, shoots, and branches was lower in nonpr uned than in pruned trees. At leaf fall, root, shoot, and branch starc h content increased in nonpruned and central leader-trained trees but did not increase in three-wire palmette-trained trees.