GROWTH AND PRODUCTIVITY OF 4 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 rip ening disease-resistant apple (Malus domestica, Borkh.) cultivars, (DR Cs), 'NY 66305-139,' 'Williams' Pride,' 'Redfree,' and 'Dayton' on M.2 6 EMLA, M.27 EMLA, or Mark rootstocks were compared. 'NY 66305-139' wa s the earliest ripening cultivar, with the smallest tree size, lowest yield, and the smallest, softest fruit. 'Williams' Pride' trees were v igorous, productive, and produced large fruit with the highest percent age of red skin color compared to the other cultivars in this trial. T he 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 me dium sized fruit. 'Dayton' trees were vigorous, high yielding, and pro duced the largest, firmest, sweetest fruit, however the September 10 r ipening date was late for a summer cultivar. Mark and M.26 EMLA produc ed similar sized trees, while M.27 EMLA produced very small trees. A s ignificant cultivar x rootstock interaction resulted from 'Dayton' tre es being larger than 'Williams' Pride' when both were on M.26, while b oth cultivars produced similar sized trees on M.27 or Mark. Of the fou r cultivars in this trial, we consider 'Redfree' to be the best summer DRC for commercial orchards, based upon ripening date, yield, and fru it quality. Mark rootstock was preferable to M.26 or M.27 for the cult ivars in this trial, with the best tree growth and precocity.