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 o n four to seven rootstocks at six sites in the midwestern and eastern Unite d States. The growth and field performance of these trees was measured over 10 years. Although some cultivar x rootstock interactions were evident, tr ee 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 a t other sites 'Rome Beauty', 'Jonagold' and 'McIntosh' trees were the large st. '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, alt hough trees on M.9 EMLA were similar in size at two sites. The smallest tre es were produced by B.9, Mark, P.22 and M.27 EMLA rootstocks. No single cul tivar 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 'McInt osh' trees had the lowest yields per tree at most sites. Yields per tree te nded to be closely related to tree size, therefore rootstocks producing the largest trees (M.26 EMLA, M.9 EMLA) also produced the largest yields. 'Yor k Imperial' and 'Stayman' trees were highly efficient, and although 'Rome' trees were efficient in some sites, they were inefficient in others. Consis tently the most efficient rootstocks were B.9, P.22, and Mark. M.26 EMLA wa s among the least efficient trees at each site. A significant negative rela tionship between tree size and yield efficiency was evident at each site, b ut the relationship differed among sites.