Performance of 'Fuji' and 'McIntosh' apple trees after 5 years as affected by several semidwarf rootstocks in the 1999 NC-140 apple rootstock trial

'Fuji' and 'McIntosh' apple trees (Malus x domestica Borkh.) on CG.4814, CG.7707, G.30N (liners from stool beds), M.7 EMLA, M.26 EMLA, and Supporter 4 rootstocks were planted at six sites with 'Fuji' and seven sites with 'McIntosh' as the scion cultivars throughout North America as a uniform trial coordinated by the NC-140 Technical Committee. Partial plantings were established at three sites per cultivar, and CG.6210 and G.30T (liners from tissue cultured plants) were included in four plantings with each scion cultivar. After five growing seasons, the only significant loss was of 'McIntosh' trees on CG.7707 (73% survived). Trunk cross-sectional area, tree height, and canopy spread were affected by rootstock and allowed partitioning of a portion of the rootstocks in this trial into preliminary size categories. CG.6210, G.30N, and G.30T resulted in semidwarf trees, similar in size to those on M.7 EMLA, but less prone to root suckering, greater yielding, and more yield efficient. CG.4814 resulted in large dwarf trees, similar in size to those on M.26 EMLA, but more prone to root suckering, greater yielding, and more yield efficient. Effects of CG.7707 and Supporter 4 varied with scion cultivar. CG.7707 resulted in semidwarf 'Fuji' trees, similar in size those on M.7 EMLA, with less root suckering, greater yield per tree, and similar yield efficiency. CG.7707 produced large dwarf 'McIntosh' trees, similar in size to those on M.26 EMLA, with slightly more root suckering and similar yield per tree, and similar yield efficiency. Supporter 4 produced large dwarf 'Fuji' trees, similar in size and performance to those on M.26 EMLA, and it resulted in semidwarf 'McIntosh' trees. similar in size to those on M.7 EMLA, with less root suckering, similar yield per tree, and greater yield efficiency.