GROWTH AND PRODUCTIVITY OF DISEASE-RESISTANT APPLE CULTIVARS ON M-27 EMLA, M-26 EMLA, AND MARK ROOTSTOCKS

The growth, precocity, yield, and fruit size of 'Liberty,' 'NY 75414-1 ,' 'NY 74828-12,' and 'NY 65707-19' on M. 27 EMLA, M. 26 EMLA and Mark rootstocks, with 'McShay' on M. 26 EMLA and Mark, were compared. 'Lib erty,' 'McShay,' and 'NY 74828-12' trees were larger than 'NY 75414-1, while 'NY 65707-19' trees were the smallest. Among rootstocks, toes o n Mark were larger than trees on M. 26, while trees on M. 27 were the smallest. There were no interactions between cultivar and root-stock o n tree growth in this study. 'NY 74528-12' produced the most flower cl usters in the third and fourth veers of the study, and NY 65707-19' th e least. In 1993, trees on Mark had more flowers than those on M. 26, while trees on M. 27 had the fewest flower clusters. 'Liberty,' 'NY 75 414-1' and 'NY 74828-12' produced higher cumulative yield than 'McShay ' and 'NY 65707-19.' Trees on Mark had higher cumulative yield than M. 26, while trees on M. 27 produced the smallest yields. Fruit size was greatest for 'NY 65707-19' and smallest for 'NY 74828-12.' Trees on M . 27 produced smaller sized fruit than trees on M. 26 or Mark.'NY 7541 4-1' had moderate vigor, high precocity, yield, and yield efficiency, with acceptable fruit size. 'NY 74825-12' also performed very well in this trial, but possesses Vm resistance to apple scab, not Vf, and is unlikely to be named. Among the disease-resistant apple cultivars (DRC ) in this trial, 'Liberty' and 'NY 75414-1,' based upon precocity, vig or, yield, and fruit size, have the best potential for commercial prod uction. Mark rootstock produced the largest trees with the highest yie lds, and was superior to M. 26 as a rootstock for the DRCs in this stu dy.