Tree size, cumulative yield, yield efficiency and anchorage of 6 micropropagated (MP) apple (Malus domestica Borkh.) cultivars were determined in 1991 after 5 years of production, as compared with trees on seedling (sdlg) or M 7a roots. Trees were planted in 1984, with crops harvested from 1987 through 1991. Trees were generally smallest (trunk cross-sectional area) on M 7a and were largest with 4 cultivars (`Delicious', `Jonathan', `Rome', `Spartan') when micropropagated. `Golden Delicious' (GD) was largest on sdlg. Cumulative yield was affected by a scion × rootstock interaction, with few trends in scion or rootstock effects. Mean cumulative yield was 84 kg tree-1, 71 and 58 for M 7a, MP and sdlg, respectively. Yield efficiency was also affected by a scion × rootstock interaction. In 1991, mean yield efficiency was 0.5 kg cm-2 for sdlg and MP trees, but was 1.05 for M 7a. Efficiency on M 7a was superior to other rootstocks with all scions except `GD', while sdlg and MP trees were statistically similar with all scions. All trees leaned in response to prevailing westerly winds, with trees on sdlg tending to be more upright than MP or M 7a trees.
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