|Authors: ||B.H. Barritt, B.S. Konishi, M.A. Dilley|
|Keywords: ||apple rootstocks, M.9 clones, cold injury, southwest trunk injury, sunscald|
Rootstock trials with Fuji (T.A.C. 114) were established in 1993 at two sites in central Washington.
The most dwarfing rootstocks, based on trunk cross-sectional area (TCA), at each site were M.27, P.22 and P.16. Twelve M.9 clones and V.3, P.2, B.9 and Mark were intermediate in tree size.
The most vigorous rootstocks in the trial were M.26, MAC.39, C6 and V.1. The ranking of rootstocks for tree size was similar at the two sites (r=.82; n=24). Cumulative fruit number per tree was generally related to tree size.
The ranking of rootstocks for cumulative fruit number per tree was generally similar at the two sites (r=.74; n=24). Rootstock influenced the extent of southwest trunk injury (sunscald) of Fuji trunks and tree mortality caused by unusually cold ( 22 to 25˚C) midwinter temperatures.
The extent of trunk injury (cm2 of sunken/dead tissue on the southwest side of the trunk) was correlated with tree mortality (r=.73; n=23). Trees on M.9 clones had the most severe injury (87 to 219 cm2 injured tissue) and tree death (33 to 68%). Rootstocks with minor or no injury (0 to 46 cm2 injured tissue) and low mortality (0 to 12%) were C6, M.27, V.1, M.26, P.22, Mark and B.9.
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