Performance of cornell-geneva rootstocks across north america in multi-location nc-140 rootstock trials

From 1992 to 1999, five multi-site replicated rootstock trials were established by the US national rootstock testing group, "NC-140". The trials compared elite Geneva apple rootstocks which were bred for tolerance to fire blight and Phytophthora root rot, high yield efficiency and good tree survival to commercial standards. The named Geneva rootstocks are designated as Geneva(TM) or "G" stocks while unnamed numbered selections from Geneva are designated as 'CG' stocks. In the 1992 plots which used 'Liberty' as the scion, Geneva(TM) 11 and CG.3029 had the highest cumulative yield efficiency, good tree survival and also had good average fruit size. They had similar tree size as M.9, but exceeded the yield performance of M.9. In contrast, Geneva(TM) 65 was more dwarfing than M.9 and had significantly lower cumulative yield efficiency and smaller fruit size than M.9. Among semi-dwarf stocks, Geneva(TM) 30, CG.6210, CG.4222 and CG.5179 all exceeded the performance of M.7 and MM.106. In the 1993 plots which also used 'Liberty' as the scion, CG.4247, CG.3041, CG.3902 and CG.3007 had the highest yield efficiencies and had good tree survival. All were similar in size to M.9, but performed significantly better than M.9 or M.26. Among the semi-dwarf stocks top performers were G.30, CG.6210, CG.222 and Geneva(TM) 202. All performed significantly better than M.7. In the 1994 plots which used Gala as the scion, Geneva(TM) 30 produced a tree similar in size to M.26 and more efficient than M.26 at 12 sites and less efficient at 6 sites. Fruit size was similar to M.26. G.30 generally had good survival; however, in 5 of 23 sites 50-60% of the trees broke off at the graft union during wind storms. In the 1998 and 1999 trials, Geneva(TM) 16 has been slightly larger than M.9 with Gala, Fuji and McIntosh, but similar to M.9 with Jonagold. Productivity of Geneva(TM) 16 has been similar to M.9 in all trials. CG.3041 has been similar in size and productivity to M.9 with Jonagold, Fuji and McIntosh.