|Authors: ||T.L. Robinson, L. Anderson, A. Azarenko, B.H. Barritt, G. Brown, J. Cline, R. Crassweller, P. Domoto, C. Embree, A. Fennell, D. Ferree, E. Garcia, A. Gaus, G. Greene, C. Hampson, P. Hirst, E. Hoover, S. Johnson, M. Kushad, R.E. Marini|
|Keywords: ||apple, Malus, rootstock, fire blight, yield efficiency, dwarfing, winter hardiness, graft union, anchorage|
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 GenevaTM or "G" stocks while unnamed numbered selections from Geneva are designated as 'CG' stocks.
In the 1992 plots which used 'Liberty' as the scion, GenevaTM 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, GenevaTM 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, GenevaTM 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 GenevaTM 202. All performed significantly better than M.7. In the 1994 plots which used Gala as the scion, GenevaTM 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, GenevaTM 16 has been slightly larger than M.9 with Gala, Fuji and McIntosh, but similar to M.9 with Jonagold.
Productivity of GenevaTM 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.
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