Influence of rootstocks on apple fruit quality

Rootstocks affect apple fruit quality not only directly but also indirectly by influencing tree vigour and crop load. Little data is available so far on the impact of various new apple root stock cultivars on fruit quality. Fruit quality is being studied in two trials at the Swiss Federal Research Station Wadenswil that include the cultivars Arlet and Jonagored on root stocks M9 EMLA, Pajam 1, Pajam 2, M9 T338 and Mac 9 (planted in 1991, 4 x 1.5 m), as well as cultivars Arlet and Fiesta on M9 EMLA, M9 T337, Budagovski 9 and P 22 (planted in 1992, 4 x 1.3 m). Two blocks of 3 trees per cultivar x rootstock combination are used on slender spindels. The trial site at 500 m above sea level is characterized by 1300 mm of annual rainfall, supporting good tree vigour, and a sandy loam with 2.5% organic matter and a pH of 6.5. External fruit quality (as calibrated by the automated calibration equipment AWETA) and internal fruit quality (sugar, acid, firmness) are estimated. In terms of fruit yield, few differences have been found until now (trial 1: season 5 and 6, trial 2: season 4 and 5). Furthermore, so far rootstock cultivars. produced fruit of similar quality.