GROWTH AND FRUIT PRODUCTION OF YOUNG MICROPROPAGATED APPLE (MALUS-DOMESTICA BORKH) TREES

Tree size, cumulative yield, yield efficiency and anchorage of six micropropagated (MP) apple (Malus domestica Borkh.) cultivars were determined in 1991 after 5 years of fruit production, as compared with trees budded on domestic seedling (sdlg) or Malling (M) 7a roots. Trees were planted in 1984, with crops harvested from 1987 through 1991. Trees of all scions except cultivar 'Rome' were smaller (as determined by trunk cross-sectional area) on M 7a than for MP trees. MP trees of cultivar 'Delicious', cultivar 'Jonathan', cultivar 'Rome' and cultivar 'Spartan' were larger than trees on sdlg, while the opposite occurred with 'Golden Delicious' (GD). Cumulative yield was affected by a scion X rootstock interaction, with few consistent trends in scion or rootstock effects. Yield efficiency was also affected by a scion X rootstock interaction. In 1991, cumulative yield efficiency on M 7a was superior to other rootstocks with all scions except GD, while the efficiency of sdlg and MP trees was statistically similar with all scions. In general, cumulative yield efficiency for M 7a was twice that for sdlg and MP trees. Nearly all trees leaned in response to prevailing westerly winds, with trees on sdlg generally more upright than MP or M 7a trees.