Quality and Storage of `Granny Smith' and `Greenspur' Apples on Seedling, M.26, and MM.111 Rootstock

Influences of rootstock on the quality of 'Granny Smith' and 'Greenspur' apples (Malus domestica Borkh.) were evaluated over an extended harvest period and after cold storage. Apples from trees on M.26 rootstock had the higher firmness, soluble solids concentration (SSC), and Ca content, but poorer external color (red blush) and a higher percentage of solar injury than fruit from trees on seedling or MM.111 rootstock. External greenness was best on apples from MM.111 rootstock. 'Granny Smith' apples had higher firmness, soluble solids, acids, and car- bohydrate contents, and less scald but poorer external greenness than 'Green spur' apples. 'Granny Smith' or 'Green- spur' apples from M.26 rootstock appeared to mature earlier than those on MM.111. Information on the influence of rootstock on the precocity, growth habit, size, and performance of apple trees is widely available (Abdalla et al., 1982; Brown et al., 1985; Denby, 1982; Larsen and Fritts, 1982). The influence of rootstock on fruit quality and storage, particularly for 'Delicious' and 'Golden Delicious', has been reported (Autio, 1987; Drake et al., 1988; Fallahi et al., 1985a, 1985b; Larsen et al., 1982). These studies on fruit quality have indicated that rootstock can influence size, firmness, color, soluble solids content (SSC), carbohydrate con- centration, ripening and maturity, storage quality, and respira- tion rate of the scion. fruit before and during storage. Nothing has been reported on the influence of rootstock on fruit quality of 'Granny Smith' and 'Greenspur' apples. 'Greenspur' is a spur type 'Granny Smith' with a reported superior skin greenness (Ballard, 1981). Although 'Granny Smith' apples are widely grown (3300 ha, Wash. State Dept. Agr., 1986) in Washington State, the length of the growing season is only marginal and development of proper greenness for good marketing can be a problem. If, as reported, rootstock can influence fruit maturity and quality characteristics, such as color, proper scion/rootstock selection can be used to advance maturity and aid in proper color devel- opment. This study was initiated to determine the influence of rootstock on the maturity and fruit quality of 'Granny Smith' and 'Greenspur' apples.