Rootstock Affect Ripening and Other Qualities of 'Delicious' Apples

load Abstract. The effects of rootstock on 'Delicious' (Malus domestics Borkh.) apple ripening, quality, size, mineral composition, and storability were studied over 4 years. Removal of the effects of crop load by analysis of covariance suggested that M.27 EMLA advanced fruit ripening and that M.7 EMLA delayed fruit ripening. Ott.3, M.9, MAC 9, OAR 1, M.9 EMLA, and M.26 EMLA either were inconsistent in their effects on ripening or consistently- resulted in an intermediate time of ripening. Fruit size consistently was largest from trees on M.9 EMLA and smallest from trees on OAR 1. Fruit from trees on MAC 9 generally had relatively high Ca contents, and fruit from trees on OAR 1 had relatively low Ca concentration s. The effects of rootstock on storability appeared to be related to their effects on maturity arid Ca levels. The effects of rootstock on apple fruit characteristics have been assessed by many researchers. Studies have shown that rootstock or interstock clone can affect apple ripening and qual- ity (Drake et al., 1988; Fallahi et al., 1985a, 1985b; Larsen et al., 1986; Lord et al., 1985; Perry and Dilley, 1984; Wallace, 1930), mineral composition (Drake et al., 1988; Jackson and Blasco, 1975), and storability (Fallahi et al., 1985b; Lord et al., 1985; Wallace, 1930). No consistent pattern of these effects emerged; however, many of these studies have included only a few rootstock, are the results of only 1 or 2 years of study, or have ignored confounding factors, such as crop load, light in- terception, and fruit size. ' The objectives of this project were to: 1) assess, over 4 years, the effects of several rootstock of varying tree size-control ca- pacities on apple ripening, quality, and size, taking into account potential confounding influences; 2) determine the effects of the same rootstock on mineral composition of apple fruit after re- moving the effects of fruit size; and 3) assess rootstock effects on apple storability.