PERFORMANCE OF 10 VIGOROUS AND SEMI-VIGOROUS APPLE ROOTSTOCKS OVER 10YEARS IN BRITISH-COLUMBIA

A trial of 'Macspur Mclntosh' on four seedling rootstocks (open-pollin ated Antonovka, open-pollinated Haralson, Antonovka x Beautiful Arcade , Haralson x Beautiful Arcade) and six clonal rootstocks (B.118, I.48- 41, M.2, M.4, M.7 and MO.56-4) was planted in 1986 to identify cold-ha rdy, yield-efficient apple rootstocks adapted to southern British Colu mbia. Spread and trunk cross-sectional area (TCA) were greatest for tr ees on MO.56-4 and smallest for trees on M.7. The height, spread and T CA of trees on the open-pollinated seedling rootstocks did not differ significantly, but TCA for trees on Haralson x Beautiful Arcade and An tonovka x Beautiful Arcade were smaller than on the open-pollinated se edling rootstocks. Trees on the M.7 were the most precocious. Cumulati ve yield was high on MO.56-4, but its cumulative yield efficiency (cum ulative yield/final hunk cross-sectional area) was among the lowest. C umulative yield efficiency and canopy efficiency (cumulative yield/can opy volume over the last five years) were highest on M.7, M.4, and I.4 8-41. B.118 was similar to M.4 in height, B.118 spread, and TCA, but s lightly lower in cumulative yield efficiency. All the seedling rootsto cks were less precocious than M.7, and lower in cumulative yield effic iency than M.7 or M.4, but not M.2. Fruits from trees on Haralson x Be autiful Arcade and Antonovka x Beautiful Arcade were among the smalles t. Rootstock did not affect the incidence of windfalls or the degree o f bienniality of the scion. I.48-41, M.7 and open pollinated Haralson produced the most root suckers. Although yield performance was good on M.7 one of the trees died and another was seriously injured by a wint er freeze during the study. Overall, M.4, B.118 and I.48-41 appear to have the greatest potential for cold sites.