PERFORMANCE OF DWARFING APPLE ROOTSTOCKS IN 5 TRIALS IN BRITISH-COLUMBIA, CANADA

Five trials of dwarf and semi-dwarf apple rootstocks were conducted, w ith the objective of identifying hardy, yield-efficient rootstocks ada pted to the regional climate, and suitable for the newer tree training methods used in high-density plantings. The rootstocks tested were: J erk 9 (J.9), Mark, Ottawa 3 (O.3), Budagovsky 9 (B.9), the Polish root stocks P.2, P.16 and P.22, and the Malling rootstocks M.4, M.9 EMLA, M .26 EMLA and M.27 EMLA. The scion varied among trials and included 'Ma cspur McIntosh,' 'Summerland McIntosh,' 'Jonagold' and 'Shamrock.' Mar k, J.9 and P.16 produced trees similar to M.9 EMLA in size and product ivity. P.16 was slightly more yield-efficient than M.9 EMLA, and avera ge fruit weight on Mark was slightly lower than on M.9 EMLA or J.9. Ma rk and J.9 were more precocious than M.9 EMLA, as judged by early blos som production. Trees of this size would be most suitable for high den sity plantings on most sites in British Columbia. O.3, B.9 and P.2 pro duced trees larger than M.9 EMLA and similar to M.26 EMLA in size. P.2 was lower in yield and yield efficiency than trees of similar size on 0.3 and B.9. O3 and B.9 were similar in all respects, except that 0.3 was more yield-efficient in one trial. M.26 EMLA was slightly more pr ecocious than O.3. 0.3; B.9 and M.26 EMLA would be useful on cold site s or where site or scion vigor is too low for M.9. P.22 and M.27 EMLA produced trees that are probably too small for conventional slender sp indle and vertical axe training. Vertical axe trees were more precocio us than supported central-leader trained trees, but not slender spindl es.