Early Field Performance of Several Self-Rooted, Micropropagated Apple Cultivars vs. Trees on Seedling or M. 7a Rootstocks

Abstract

Tree size and yield of several self-rooted (from micropropagation) apple cultivars planted in 1984 were compared in 1987 and 1988 with trees on seedling and M. 7a stocks. In both years, trees were generally smallest on M. 7a. ‘Jonathan,’ ‘Rome,’ and ‘Spartan’ were usually largest when self-rooted; ‘Golden Delicious’ and ‘McIntosh’ tended to be largest on seedling roots. In 1987, yield of all cultivars was generally highest on M. 7a, with few differences between self-rooted trees and trees on seedling. By 1988, rootstock had no significant effect on yield. Except for ‘Spartan’ and ‘Delicious,’ yield efficiency in 1987 was significantly higher on M. 7a than on the other roots. By 1988, yield efficiencies were 0.21, 0.31, and 0.36 kg cm ⁻²for self-rooted, seedlings, and M. 7a, respectively, but the differences were not significant. Nearly all trees leaned in response to a prevailing westerly wind, with trees on seedling tending to be more upright (16° from vertical) than micropropagated trees (21°) or those on M. 7a (23°). There was, however, a cultivar/rootstock interaction for anchorage. The most poorly anchored combination was ‘Spartan’/M. 7a (39°) while ‘Spartan’/sdlg and ‘McIntosh’/M. 7a were among the best anchored combinations (13.5° and 15.0°, respectively).