Early Performance of 'Honeycrisp' Apple Trees on Several Size-Controlling Rootstocks in the 2014 NC-140 Rootstock Trial

In 2014, a multi-year orchard experiment of apple Malus domestica (Borkh) was established at 14 locations in Canada, Mexico, and the United States using 'Honeycrisp' as the scion. Seventeen dwarf and semi-dwarf rootstock genotypes were tested, specifically: Budagovsky.10 (B.10), the Cornell-Geneva rootstocks G.11, G.202, G.214, G.30, G.41, G.890, G.935, G.969, the Malling rootstocks M.7, MM.106, and the Vineland rootstocks V.1, V.5, V.6, and V.7. The industry standard Malling rootstocks M.26 EMLA and M.9-T337 were included for comparison purposes. Tree mortality, trunk cross-sectional area, tree canopy size, amount of rootstock suckering, yield, and fruit number were measured annually. All measured parameters were influenced by location and rootstock, and the interaction of these two factors was significant. Overall, after five years and averaged over all locations, G.11 and G.41 were 6% smaller and 5% larger, respectively, than M.9-T337. G.935 and B.10 were 9% and 5% smaller, respectively, than M.26 EMLA, whereas G.214 and G.969 were 3% and 10% larger, respectively. V.1 and G.30 were 52% and 60% larger, respectively, than M.26 EMLA, whereas V.7, G.890, V.6, and V.5 were the largest genotypes in the trial, ranging from 77-95% larger than M.26 EMLA. G.202 performance was unusual and therefore was omitted from data analysis. Generally, cumulative yields per tree were greater on trees with the highest vigor. On average, 10 of the 16 rootstocks produced higher yields than M.9-T337 and M.26 EMLA; the newer rootstocks B.10, V.5, V.6, V.7 and all of the Geneva series rootstocks, with the exception of G.41, had cumulative yields that exceeded M.9-T337 and M.26 EMLA. Averaged over all locations, cumulative yield efficiency was greatest for G.935, G.214, M.9-T337, G.11, G.890, and G.969. Overall, the strong rootstock by location interaction on cumulative yield observed in this trial illustrates the importance of testing rootstocks at a regional level. These results are only reflective of the orchard establishment years; additional research must be completed before apple producers can make more informed decisions concerning rootstock selection for their orchard training systems and planting locations.