Influence of Rootstocks on Scion Growth and Leaf Mineral Content of Apple (Malus pumila 'Golden Delicious' and 'Red Gala') Trees

The vegetative and reproductive performances of 'Golden Delicious' and 'Red Gala' apples (Malus pumila L.) grown on four rootstocks (seedling, M. 9, MM. 106, and MM. 111) were studied during a 4 year period (2006 to 2009). Effects of rootstock on fruit number, fruit weight, yield, yield efficiency (kg/m(3)) and fruit quality (TSS, firmness) of apple scions showed significant differences (P=0.05). The most vigorous trees were on seedling rootstocks, followed by MM. 111, MM. 106 and M. 9 rootstocks. There were negative correlations between their trunk cross section areas (TCSA), and yield efficiencies (kg tree(-1) TCSA(-1)). The highest cumulative yields per tree were harvested from 'Golden Delicious' trees grafted on seedling rootstock (28, 34, 49, and 113 kg/yr). The lowest cumulative yield was recorded for 'Red Gala' trees grafted on M. 9 rootstock. The effect of rootstock on the major minerals (N, K, Mg, Ca, Fe, and Mn) concentrations (sampled over three years) of plant tissue was significant (P=0.05). Leaf tissue analysis showed that different rootstocks had different mineral uptake efficiencies throughout the season. Both cultivars 'Red Gala' and 'Golden Delicious' grafted on seedling rootstock were among the highest in leaf Ca and K, whereas those on M. 9 rootstock were the most efficient in N, Mn, and Fe uptake. M. 9 supported the lowest uptake of K and Ca and MM. 106, the highest uptake of P throughout the season.