Growth and productivity of four summer ripening disease-resistant apple cultivars on M.27 EMLA, M.26 EMLA and Mark rootstocks

The growth, productivity, and fruit characteristics of four summer ripening disease-resistant apple (Malus domestica, Borkh.) cultivars, (DRCs), 'NY 66305-139,' 'Williams' Pride,' 'Redfree,' and 'Dayton' on M.26 EMLA, M.27 EMLA, or Mark rootstocks were compared. 'NY 66305-139' was the earliest ripening cultivar, with the smallest tree size, lowest yield, and the smallest, softest fruit. 'Williams' Pride' trees were vigorous, productive, and produced large fruit with the highest percentage of red skin color compared to the other cultivars in this trial. The presence of moldy core and bitter pit in 1996, raise concerns about its commercial potential. 'Redfree' trees were intermediate among the four cultivars in vigor and precocity, and produced high yields of medium sized fruit. 'Dayton' trees were vigorous, high yielding, and produced the largest, firmest, sweetest fruit, however the September 10 ripening date was late for a summer cultivar. Mark and M.26 EMLA produced similar sized trees, while M.27 EMLA produced very small trees. A significant cultivar x rootstock interaction resulted from 'Dayton' trees being larger than 'Williams' Pride' when both were on M.26, while both cultivars produced similar sized trees on M.27 or Mark. Of the four cultivars in this trial, we consider 'Redfree' to be the best summer DRC for commercial orchards, based upon ripening date, yield, and fruit quality. Mark rootstock was preferable to M.26 or M.27 for the cultivars in this trial, with the best tree growth and precocity.