Evaluation of a Spur and a Standard Strain of ‘McIntosh’ on Three Rootstocks and One Dwarfing Interstem Over Ten Years

Abstract

Performance of ‘Rogers Red McIntosh’ and ‘Macspur’ was evaluated on M.7A, M.26, M.9, and M.9/MM.111 rootstocks. Trees on M.9 were either staked or trained to a 2.1-m vertical trellis. After 10 years, trees on M.7A were the largest. Those on M.26 and M.9/MM.111 were similar in size, and trees on M.9 were the smallest. ‘Rogers’ trees were larger than ‘Macspur’ trees. Trees on M.9 were the most precocious, with the greatest bloom and fruit set in the third and fourth growing seasons. Trees on M.7A yielded the most fruit through the tenth season, followed by those on M.26. Staked trees on M.9 yielded the least. ‘Rogers’ yielded more than ‘Macspur,’ but yield efficiency was greater for ‘Macspur’ than ‘Rogers.’ The most yield efficient trees were trellised and on M.9, significantly more efficient than staked trees on M.9. Trees on M.26 and M.9/MM.111 were less efficient than those on M.9, but were significantly more efficient than trees on M.7A. Tree spread was used to calculate potential tree density and potential yield per hectare. The greatest potential yields per hectare would be from trellised trees on M.9, the lowest yields would be from trees on M.9/MM.111. Trees on M.7A, M.26, and M.9 (staked) would produce intermediate and similar yields per hectare over the first 10 growing seasons. ‘Macspur’ would outyield ‘Rogers.’ The most surface red color was obtained on fruit from trees on M.9/MM.111. Fruit from trees on M.9 and M.26 were similarly colored, and the least red color occurred on fruit from trees on M.7A. ‘Macspur’ fruit were more highly colored than ‘Rogers’ fruit. Fruit weight was greatest for trees on M.9.