Performance of ‘Gala’ Apple Trees on Supporter 4, P. 14, and Different Strains of B.9, M.9 and M.26 Rootstocks: A Five-Year Report on the 2002 NC-140 Apple Rootstock Trial

Abstract

In 2002, an orchard trial of apple rootstocks was established at nine locations in Canada, Mexico, and the United States using ‘Buckeye Gala’ as the scion cultivar. Rootstocks included B.9 (North American or Treco strain), B.9 (European strain), M.26 NAKB, M.26 EMLA, M.9 Burgmer 756, M.9 Nic 29, M.9 NAKBT337, P.14, and Supporter 4. After 5 years, the greatest mortality was for trees on M.9 NAKBT337 (33%), and the lowest was for trees on M.26 NAKB (13%), B.9 Treco (13%), and B.9 Europe (10%). P.14 resulted in the largest trees based on trunk cross-sectional area. Smallest trees were on the two B.9 strains, with the European strain significantly smaller than the North American strain. Largest trees in the intermediate group were on Supporter 4, followed by those on M.26 NAKB, M.26 EMLA, M.9 Burgmer 756, M.9 Nic 29, and M.9 NAKBT337. Burr knot severity was highest on B.9 Europe and the two strains of M.26 compared to all other rootstocks. The severity of burr knots on the European strain of B.9 (20% of the circumference affected) was significantly greater than on the North American strain (7% of the circumference affected). Trees on M.26 NAKB, M.9 NAKBT337, and M.9 Nic 29 yielded more (cumulatively, 2004-06) than those on P.14 or B.9 Europe. The most yield efficient trees (cumulatively, 2004-06) were on the two B.9 strains, and the least efficient were on P.14. On average over the first 3 years of fruiting, M.9 Burgmer 756 resulted in larger fruit than did B.9 Europe or M.26 NAKB.