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. 'Liberty,' 'McShay,' and 'NY 74828-12' trees were larger than 'NY 75414-1,' while 'NY 65707-19' trees were the smallest. Among rootstocks, trees on Mark were larger than trees on M. 26, while trees on M. 27 were the smallest. There were no interactions between cultivar and rootstock on tree growth in this study. 'NY 74828-12' produced the most flower clusters in the third and fourth years of the study, and 'NY 65707-19' the 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 75414-1' 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 75414-1' had moderate vigor, high precocity, yield, and yield efficiency, with acceptable fruit size. 'NY 74828-12' 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, vigor, yield, and fruit size, have the best potential for commercial production. Mark rootstock produced the largest trees with the highest yields, and was superior to M. 26 as a rootstock for the DRCs in this study.