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J.R. Schupp and S.I. Koller

The growth, productivity, and fruit characteristics of four summer-ripening disease-resistant apple 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 large, productive, and produced large fruit with the highest red skin color in this trial. The loss of marketable yield of this cultivar, due to 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 large, high-yielding, and produced the largest, firmest, sweetest fruit; however, the ripening date for `Dayton' was 10 Sept., late for a summer cultivar. Mark and M.26 EMLA produced similarsized trees, while M.27 EMLA produced very small trees. A significant cultivar × 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.

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J.R. Schupp and S.I. Koller

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, and `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 3rd and 4th 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 well in this trial, but possesses Vm resistance to apple scab, not Vf, and is unlikely to be named. Based on tree vigor, percocity, yield, and fruit size, `Liberty' and `NY 75414-1' have the best potential for commercial production among DRCs in this trial. 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.

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J.R. Schupp, S.I. Koller and W.D. Hosmer

This study was undertaken to test the efficacy of a power duster for supplemental pollination of `McIntosh' apple trees, where lack of nearby pollinizing cultivars was thought to be a limiting factor to productivity. The pollen duster was ineffective in increasing fruit set, fruit size, or seed number in fruits on limbs that were covered with spun-bonded rowcover material prior to bloom. Applying supplemental pollen to open-pollinated `McIntosh' trees had no effect on fruit set, yield, fruit size, or seed number, regardless of pollen dose, timing, or number of applications. Dispersal of supplemental pollen with a power duster appears to be an inefficient method of pollinating apple trees.

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J.R. Schupp, S.I. Koller and W.D. Hosmer