Performance of Three Apple Cultivars with 23 Dwarfing Rootstocks During 8 Seasons in Washington

Abstract

The performance of 23 apple rootstocks was evaluated with cultivars Golden Delicious, Granny Smith and Delicious during eight seasons. Rootstocks in the trial, listed in order of increasing tree vigor when measured as trunk cross-sectional area (TCA), were M.27 EMLA, P.16, Mark, V.3, MAC.9, P.22, B.146, M.9, CG.10, P.2, M.9 EMLA, V.1, B.9, O.3, MAC.39, M.26 EMLA, V.7, C6, V.2, M.7A, OAR.1, V.4 and P.1. There was little change in ranking of rootstocks for TCA after year 3 and the ranking of rootstocks was essentially similar with each cultivar. Root suckers were most numerous with MAC.9, V.4, B.146, Mark, P.1 and M.7A. The most precocious rootstocks, based on second year bloom and third year production, were M.9 EMLA, O.3, V.7, B.9, V.1, MAC.9 and M.9, and the least precocious rootstocks were OAR.1, M.7A, P.1, V.4, CG.10, B.146 and M.26 EMLA. With each cultivar, cumulative yield/tree to year 8 increased as rootstock vigor increased. Cumulative yield efficiency (kg yield/cm ²TCA) at year 8 was generally highest for the most dwarfing rootstocks (V.3, P.16, B.9, P.22, M.9, MAC.9, B.146, M.9 EMLA, P.2, Mark, O.3 and V.1) and lowest for the most vigorous rootstocks (OAR.1, P.1, V.4, M.7A and C6). There was little change in the ranking of rootstocks for cumulative yield efficiency from year 6 onward and the ranking of rootstocks was generally similar with each cultivar. With ten rootstocks (B.9, O.3, M.26 EMLA, V.7, P.22, V.1, P.2, V.3, MAC.39 and M.9) mean fruit weight adjusted for crop load was not different from M.9 EMLA during six seasons with three cultivars. Rootstocks with the lowest fruit weight were Mark, M.27 EMLA, MAC.9, P.1 and OAR.1. Biennial bearing of Golden Delicious and Granny Smith was more pronounced with vigorous than with dwarfing rootstocks. With Delicious biennial bearing was generally greatest with the more dwarfing rootstocks.