Performance of 'Gala' apple trees on 18 dwarfing rootstocks: Ten-year summary of the 1994 NC-140 rootstock trial

Eighteen dwarfing rootstocks, including six M.9 clones and two Vineland selections, were compared at 25 North American locations for 10 years. For most response variables, there was a highly significant location x rootstock interaction, so rootstock performance differed greatly from one location to another. The M.9 clones tested in this study had similar tree survival and yield efficiency (YE), but there were large differences in tree vigor. M.9 Pajam 2 and M.9 RN29 were nearly as vigorous as M.26, whereas M.9 Flueren 56 was least vigorous. Rootstocks could be grouped into five size categories. The most dwarfing rootstocks included P.22, M.27, P.16 and B.491, and these likely lack adequate vigor for commercial production. The second most dwarfing group of rootstocks were B.469 and Mark which produce trees of similar size. A group of slightly more vigorous rootstocks included V.3, B.9 and M.9 Flueren 56. Rootstocks similar in vigor to M.9 NAKBT337 included P.2, M.9 EMLA, M.9 Pajam 1, and O.3. The most vigorous group of rootstocks in the M.26 size class included M.9 RN29, M.9 Pajam 2, and V. 1. Cumulative yield tended to be positively related to tree size, but had relatively low yields for its size. YE was significantly affected by rootstock at 14 locations. Trees on Mark had high YEs at most locations, whereas trees on B.491 had low YEs at many locations.