|Authors: ||W. Autio, T.L. Robinson, W. Cowgill, C. Hampson, M. Kushad, G. Lang, J. Masabni, D.D. Miller, R.A. Parra-Quezada, R. Perry, C. Rom|
|Keywords: ||Malus × domestica, yield efficiency, tree size, fruit size|
In spring 2002, a North American-wide trial of apple rootstocks was established under the coordination of NC-140. ‘Buckeye Gala’ (Malus × domestica) was used as the scion cultivar, and rootstocks included B.9 North America (the strain commonly used in North America), B.9 Europe (the strain commonly used in Europe), M.26 EMLA, M.26 NAKB, M.9 Burgmer 756, M.9 Nic 29, M.9 NAKBT337, and Supporter 4. The trial was planted in Arkansas, British Columbia (Canada), Chihuahua (Mexico), Illinois, Kentucky, Massachusetts, Michigan, New Jersey, New York, and Ohio.
Trees were spaced 2.5×4.5 m and trained as vertical axes.
After six growing seasons, smallest trees were on the two B.9 strains and trees on B.9 Europe were significantly smaller than those on B.9 North America.
Supporter 4, M.26 EMLA, M.26 NAKB, and M.9 Burgmer 756 were similar and resulted in the largest trees, followed by M.9 Nic 29 and M.9 NAKBT337, in descending trunk cross-sectional area.
Trees on M.26 NAKB, M.26 EMLA, and Supporter 4 cumulatively (2004-07) yielded more than those on B.9 Europe.
The most cumulatively yield efficient trees were on the two B.9 strains, significantly more than trees on any of the other rootstocks (all of which were similar). Over the 2004-07 fruiting life of the trial, rootstock did not affect fruit size.
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