Relationships of Apple Rootstock Mediated Nutrient Concentrations in Leaves and Fruit of Gala Apples

Diverse apple rootstocks possess different capacities to absorb mineral nutrients from soil and transfer them to the grafted scion variety.  A replicated field experiment of Gala scion grafted onto a population of 186 rootstocks (progeny of Ottawa 3 x Robusta 5) segregating for many apple important apple rootstock traits was used to monitor the dry matter concentration of nitrogen (N), potassium (K), phosphorous (P), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu) manganese (Mn) and aluminum (Al) in mature leaf and immature fruit tissue.  Correlation analysis revealed many significant relationships among mineral nutrients in fruit and leaves.  Leaf and fruit P and K and leaf Mg were positively correlated and trunk cross sectional area was negatively correlated with fruit concentration of S, N, Cu, Mg in order of decreasing effect and significance.  Trunk cross sectional area was positively correlated with leaf concentration of K, P and Ca in order of decreasing effect and significance. Rootstocks with different abilities to increase uptake of NPK and micro-nutrients in leaves and fruit might have a significant effect on the productivity of the orchard as well as fruit size and quality during storage.  Given the importance of fruit calcium concentrations to post-harvest fruit quality, increasing the availability of calcium and other important nutrients to growing fruit is a major target for this research.  We describe how these relationships may be used in breeding new rootstocks tailored to nutrient needs of commercial apple varieties.