Performance of 'McIntosh' apple trees on seven rootstocks and a comparison of methods of productivity assessment

Abstract

'Summerland Red McIntosh' apple trees (Malus domestica Borkh.) on M.9/A.2, O.3. M.7 EMLA, M.26 EMLA, M.7A, OAR1, and Mark were evaluated over 10 years. Trees on M.7 EMLA and OAR1 were the largest, and trees on Mark were the smallest. Trees on M.7 EMLA produced the highest yields per tree, and those on OAR1 and Mark produced the lowest. The must yield-efficient trees were on O.3 and Mark. The least efficient trees were on OAR1. Fruit from trees on O.3, M.26 EMLA, or M.9/A.2 generally were the largest, and fruit from trees on OAR1 generally were the smallest. Red pigment development was inversely proportional to canopy size, with Mark resulting generally in the most red pigmentation and M.7 EMLA and M.7A generally resulting in the least. Methods of presenting productivity were compared. Presentation of yield per land area occupied or projected yield per planted area were biased in experiments where only some trees naturally would exceed the allotted space and, therefore, were containment pruned and where tree-to-tree competition was directly proportional to tree size. Yield efficiency was a less biased estimate. Further, in single-row planting systems with trees spaced at optimal densities, small trees most he more efficient than large trees to obtain similar yields.