Performance of 'Gala' apple on 18 dwarf rootstocks: Five-year summary of the 1994 NC-140 dwarf rootstock trial

In 1994, trees of 'Gala' apple (Malus x domestica Borkh.) on 18 dwarf rootstocks were planted at 26 sites in North America according to the guidelines established for cooperative testing by the North Central Regional Cooperative Project (NC-140). Rootstocks for this trial included six selections of M.9, two from the Budagovski (B) series, three stocks from the Polish (P) series and two from the Vineland (V) series. M.27 EMLA, B.491, P.16 and P.22 produced the smallest trees, whereas V.1, M.26 EMLA, M.9 RN29 and M.9 Pajam2 produced the largest trees. M.9 EMLA, M.9 Pajam1, B.9, O.3, P.2, Mark, B.469, V.3, M.9 Fleuren 56, and M.9 NAKBT337 produced intermediate-size trees. Among the most dwarfing rootstocks, cumulative yields were greatest for P.16 and P.22, whereas M.27 EMLA had the lowest yields. All rootstocks in the intermediate size class produced similar yields. Among the most vigorous rootstocks, Pajam2 had the lowest yields and V.1 had the highest yields. Yield efficiency (YE) was low at CO, IN, NB, NC NJ, OH, SC, and ME and high at AR, OR, WA, and WI. Rootstocks significantly influenced YE at 19 of the 26 locations. Among the most dwarfing rootstocks, P.16 had the highest YE. Among the rootstocks in the intermediate size class, O.3, Mark, and M.9 NAKBT337 had the highest YE M.26 EMLA had the lowest YE for the most vigorous stocks.