Performance of several semi-dwarfing rootstocks with 'Fuji' and 'McIntosh' as Scion cultivars in the 1999 NC-140 semi-dwarf apple rootstock trials

In spring, 1999, two trials of semi-dwarf apple (Malus × domestica) rootstocks were established under the coordination of the NC-140 Technical Committee. One trial included 'Fuji' as the scion cultivar, and the other included 'McIntosh'. Rootstocks were CG.4814, CG.7707, Geneva® (G) 30N (liners from stool beds), M.7 EMLA, M.26 EMLA, and Supporter 4. The 'Fuji' trial was planted in Kentucky, Missouri, and North Carolina, with a partial planting in South Carolina. The 'McIntosh' trial was planted in Massachusetts, Michigan, Minnesota, Nova Scotia, New York (Williamson), and Ontario, with partial plantings in New York (Peru), Pennsylvania (Rock Springs), and Vermont. Trees were spaced 4×6 m and trained as free-standing central leaders. 'Fuji' trees on M.7 EMLA had larger trunk cross-sectional area in 2007 than those on Supporter 4. 'McIntosh' trees on M.7 EMLA and Supporter 4 were larger than those on M.26 EMLA, CG.4814, or CG.7707. Root suckering (cumulative, 1999-2007) was much more prominent with 'Fuji' as the scion cultivar than with 'McIntosh'. M.7 EMLA resulted in the most root suckering with both scion cultivars, and M.26 EMLA resulted in the least. Cumulatively (2001-07), 'Fuji' trees on G.30N yielded more than those on M.26 EMLA, CG.4814, M.7 EMLA, or Supporter 4. 'McIntosh' trees on G.30N, Supporter 4, M.7 EMLA, and CG.4814 yielded more than those on M.26 EMLA. Cumulatively (2001-07), 'Fuji' trees on G.30N and Supporter 4 were more yield efficient than those on M.7 EMLA. For 'McIntosh', however, trees on CG.4814 were more yield efficient than all others, and trees on G.30N and CG.7707 were more efficient than those on M.7 EMLA. On average over the fruiting life of the trial (2001- 07), fruit size was not affected by rootstock for either cultivar.