Experiment 2 : Performance of Honeycrisp and Royal Gala on the Commercial and New (Vineland Series) Size Controlling Apple Rootstocks

Ten trees each of Royal Gala and Honeycrisp on eight rootstocks (PI.80, M.26 EMLA, V.1, V.3, M.9 Nic. 29, Pajam 2, CG.16, M.9 T337, M.9 EMLA, Bud.9) were planted in a sandy silt-loam soil in 2002 at the Horticultural Experiment Station, Simcoe, Ontario. Trees were spaced 2.5 m within and 5.0 m between rows (800 trees/hectare; 323 trees/acre). Trees were trained to a vertical axe central leader system and were trickle irrigated. Results after seven years of production indicate the following:
Honeycrisp (Figure 2)

• Eight rootstocks (Bud.9, M.9 EMLA, M.9 T337, CG.16, V.3, Pajam 2, and M.9 Nic29) were significantly smaller than M.26 EMLA. PI.80, also known as Supporter 4, and V.1 were statistically similar in size to M.26 EMLA.
• Tree size (trunk cross-sectional area) ranged from 62 to 110% relative to M.26E with Bud.9 being the smallest
• Cumulative yields after 7 years were not statistically different among rootstocks. However, Bud.9, M.9 EMLA, and CG.16 were among the most yield efficient while PI.80 significantly less yield efficient.
• Cumulative yield efficiency has been significantly lower on PI.80 and M.26 EMLA in comparison with the other rootstocks
• In other Honeycrisp research conducted at the Horticultural Experiment Station, Simcoe, trees on M.26 or equivalent vigour have been preferred over M.9 because Honeycrisp is a very weak grown cultivar. However, when grafted on M.26, Honeycrisp grafted unions have had a tendency to break.