Early performance of 'Cortland,' 'Macoun,' 'McIntosh,' and 'Pioneer Mac' apple trees on various rootstocks in Maine, Massachusetts, and Nova Scotia

Trials were established in 1995 at three sites in the northeast region of North America, which included four apple (Malus X domestica Borkh.) cultivars ('Cortland,' 'Macoun,' 'Rogers Red McIntosh,' and 'Pioneer Mac') in all combinations on 10 rootstocks (B.146, B.469, B.491, M.9, M.9 NAKBT337, Mark, P.2, P.16, V.1, and V.3). Tree survival was high after five growing seasons except for trees on B.146 and B.491 in Maine and Massachusetts. Poor tree quality at planting probably explains most of the tree loss on these stocks. Tree size was not affected by cultivar or location, but was dramatically affected by rootstock. The largest trees were on Mark followed by V.1. The smallest trees were on B.469, B.491, and B.146. The M.9 clones, P.2, and V.3 were intermediate in size and similar in trunk cross-sectional area. The difference between the largest and the smallest trees was nearly seven-fold in Massachusetts and only three-fold in Maine and Nova Scotia. Cumulative yield and yield efficiency were greater in Massachusetts than at the other two sites. Trees on Mark had the greatest yield followed by V.1, M.9, V.3, M.9 NAKBT337, and P.2. Trees on B.469, B.491, B.146, and P.16 were the least productive. Trees on P.16 had the highest yield efficiency followed by trees on V.3, P.2, B.491, M.9, and M.9 NAKBT337. The least efficient trees were on B.469, Mark, V.1, and B.146. Fruit size was larger in Massachusetts than in Maine or Nova Scotia. Rootstock effects on fruit size of 'Cortland,' 'McIntosh,' and 'Pioneer Mac' were similar, with the largest fruit from trees on V.1, M.9, and V.3 and the smallest from trees on B.146. Rootstock did not affect fruit size of 'Macoun.' Several interactions between cultivar, rootstock, and location for the measured parameters were significant, but the level of variation explained by these interactions was small, compared to that explained by the main factors, and the practical importance of these interactions was minimal.