Performance of 'Fuji' and 'McIntosh' Apple Trees after 10 Years as Affected by Several Dwarf Rootstocks in the 1999 NC-140 Apple Rootstock Trial

'Fuji' and 'McIntosh' apple trees (Malus x domestica Borkh.) on Geneva (R) 41 (G.41), CG.4013, CG.5179, Geneva (R) 202 (G.202). Geneva (R) 16 (G.16) (N, liners from normal stool beds; T, liners from stool beds established with tissue cultured plants), M.9 NAKBT337, M.26 EMLA, Supporter 1, Supporter 2, and Supporter 3 rootstocks were planted at several sites per cultivar throughout North America as a uniform trial coordinated by the NC-140 Multi-State Research Committee. Partial plantings were established at two sites per cultivar. Geneva (R) 935 (G.935) was included in two 'Fuji' and four 'McIntosh' plantings. After ten growing seasons, 'Fuji' mortality was greater than 'McIntosh,' and trees on M.9 NAKBT337 showed the greatest loss, with more than 35% mortality. Tree size measurements of trunk cross-sectional area, tree height, and canopy spread were all affected by rootstock and were used to allocate each rootstock into one of four size categories. Trees on CG.4013 were semidwarfs, larger than those on M.26 EM LA. Trees on G.202 and G.935 were large dwarfs, similar in size to M.26 EMLA. Trees on CG.5179, G.41, G.16N, and G.16T were moderate dwarfs, between trees on M.26 EM LA and M.9 NAKBT337 and likely similar to the larger M.9 clones. Trees on Supporter 1, Supporter 2, and Supporter 3 were small dwarfs, similar in size to trees on M.9 NAKBT337. Burr knot development was reasonably low but affected the greatest portion of the rootstock shank's circumference of both 'Fuji' and 'McIntosh' trees on CG.5179, G.16N, and G.16T. Root suckering was greatest from 'Fuji' trees on CG.4013, CG.5179, G.202, and M.9 NAKBT337. Very little root suckering was seen with 'McIntosh,' but the greatest numbers were from trees on CG.4013, CG.5179, and M.9 NAKBT337. Cumulative yield per tree was positively related to tree size. The most yield efficient 'Fuji' trees were on CG.5179, G.41, and Supporter 1, and the least efficient were on M.26 EM LA and CG.4013. The most yield efficient 'McIntosh' trees were on Supporter 1, Supporter 2, Supporter 3, G.41, and CG.5179, and the least efficient were on G.202, M.26 EM LA, and CG.4013. Average fruit weight was only modestly affected by rootstock. Generally, trees on G.41, M.9 NAKBT337, and M.26 EMLA had the largest fruit size, while trees on Supporter 2 and Supporter 3 had the smallest fruit size.