Performance of trees in the 1990 NC-140 apple cultivar/rootstock planting: Additional cultivars and rootstocks

In 1990, up to 10 apple (Malus X domestica Borkh.) cultivars were planted on four to seven rootstocks at six sites in the midwestern and eastern United States. The growth and field performance of these trees was measured over 10 years. Although some cultivar x rootstock interactions were evident, tree growth and performance was primarily due to the main effects of cultivar and rootstock. Cultivar had no effect on tree size at three sites, while at other sites 'Rome Beauty', 'Jonagold' and 'McIntosh' trees were the largest. 'Stayman' and 'Empire' trees were among the smallest trees across sites. Trees growing on M.26 EMLA were among the largest trees at all sites, although trees on M.9 EMLA were similar in size at two sites. The smallest trees were produced by B.9, Mark, P.22 and M.27 EMLA rootstocks. No single cultivar produced the highest yield at all sites. 'Golden Delicious' was among the most productive cultivars at three sites, but performed only moderately or poorly at other sites. 'Empire' and 'McIntosh' trees had the lowest yields per tree at most sites. Yields per tree tended to be closely related to tree size, therefore rootstocks producing the largest trees (M.26 EMLA, M.9 EMLA) also produced the largest yields. 'York Imperial' and 'Stayman' trees were highly efficient, and although 'Rome' trees were efficient in some sites, they were inefficient in others. Consistently the most efficient rootstocks were B.9, P.22, and Mark. M.26 EMLA was among the least efficient trees at each site. A significant negative relationship between tree size and yield efficiency was evident at each site, but the relationship differed among sites.