Performance of Three Apple Cultivars with 22 Dwarfing Rootstocks During 8 Seasons in Ohio

Abstract

Rootstocks in this trial produced a continuum in tree size that could logically be grouped with the Malling standards as follows: M.27 size group = B.146, P.16, P.22, Mark and MAC.9; M.9 size group = B.9, V.1, V.3, P.2, M.9EMLA, CG.10, MAC.39 and C6; M.26 size group = V.2; M.7 size group P.1, V.4, V.7, OAR1. The virus-free selections M.9EMLA and Mark did not differ significantly in size or cropping from the original selection of M.9 and MAC.9, respectively. In general, as tree size increased, trunk crosssectional area (TCA) growth increment was greater as the trees aged. The following rootstocks had relatively high biennality indexes on both 'Macspur Mclntosh' and 'Redchief Delicious' the most biennial cultivars in this trial: CG.10, M.9, MAC.39, V.2, V.4, V.7, M.7EMLA. 'Macspur Mclntosh' on OAR1 was characterized by having long shoots and large numbers of non-flowering spurs, while 'Macspur Mclntosh' on Mark, M.27EMLA and MAC.9 tended to have short shoots and the fewest non-flowering spurs and vegetative shoots. The following rootstocks tended to increase the density of flowering spurs on 'Macspur Mclntosh': M.9, M.26EMLA, V.4, M.7EMLA and V.1. 'Lawspur Rome Beauty' was the most productive and efficient with tne lowest bienniality index and was intermediate in tree size and TCA change compared to 'Macspur Mclntosh' and 'Redchief Delicious.'