|Authors: ||T. Robinson, L. Anderson, A. Azarenko, B. Barritt, T. Baugher, G. Brown, G. Couvillon, W. Cowgill, R. Crassweller, P. Domoto, C. Embree, A. Fennell, E. Garcia, A. Gaus, R. Granger, G. Greene, P. Hirst, E. Hoover, S. Johnson, M. Kushad|
|Keywords: ||apple, Malus x domestica, rootstock, fire blight, yield efficiency, dwarfing, winter hardiness, graft union, anchorage|
In 1992 and 1993 a series of multi-site replicated rootstock trials were established by the US national rootstock testing group, “NC-140,” using ‘Liberty’ as the scion.
The trials compared elite Geneva apple rootstocks which were bred for tolerance to fire blight and Phytophthora root rot 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 among dwarfing rootstocks, ‘GenevaTM11’ (‘G.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’. ‘GenevaTM202’ (‘G.202’) had slightly lower yield efficiency than ‘G.11’ and was similar to ‘M.9’. Tree size of ‘G.202’ was slightly larger than ‘M.9’. In contrast, ‘GenevaTM65’ was more dwarfing than ‘M.9’ and had significantly lower cumulative yield efficiency and smaller fruit size than ‘M.9’. Among semi-dwarf stocks, ‘GenevaTM30’, CG.6210, CG.4222, CG.5179 and CG.5517 all exceeded the performance of ‘M.7’ and ‘MM.106’. Among vigorous stocks, CG.6002, CG.6239 and CG.8189 all exceeded the performance of ‘MM.111’. ‘Novole’ was significantly more vigorous than ‘MM.111’ and less productive.
In the 1993 plots, 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’. CG.4247 had smaller fruit size than ‘M.9’. ‘G.65’ again produced a smaller tree and smaller fruit size than ‘M.9’, but yield efficiency was similar to ‘M.9’. ‘G.11’ performed poorer than ‘M.9’ or ‘M.26’ in this plot.
Among the semi-dwarf stocks, top performers were ‘G.30’, CG.6210, CG.4222 and ‘G.202’. All performed significantly better than ‘M.7’. Among vigorous stocks, top performers were CG.7760, CG.6239, CG.6253, CG.8189 and CG.7707. All performed significantly better than ‘MM.111’.
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