INFLUENCE OF ROOTSTOCK ON NUTRIENT ACQUISITION BY PISTACHIO

The influence of rootstock selection on leaf nutrient concentrations in commercial pistachio (Pistacia vera cv. 'Kerman') was studied. Five commercially important pistachio rootstocks were used. The pistachio rootstock Pistacia atlantica was clearly superior in enhancing leaf concentrations of the elements, boron (B), copper (Cu), zinc (Zn), and phosphorus (P) from a range of soil types. The influence of rootstock on leaf nutrient concentration was apparent both in grafted and non-grafted trees and was most pronounced when leaf nutrient levels were low. Leaf B, Cu, and Zn concentrations were from 1.2 to 2.4 times higher in pistachio grafted to P. atlantica than in those grafted on other rootstocks. For Cu and Zn, elements that are often deficient in Californian pistachio orchards, the choice of rootstock was sufficient to overcome visual deficiencies of these elements. In soils low in a particular element selection of rootstock may significantly influence management decisions and the need for fertilizer supplementation. Two hybrid rootstocks, in which the efficient rootstock P. atlantica was crossed with the inefficient P. integerrima, had lower leaf nutrient concentrations than the P. atlantica parent. The mechanism of nutrient efficiency was not identified though correlation analysis suggests separate characteristics are responsible for the enhancement of Zn uptake as compared to B or Cu uptake. Improvement in nutrient efficiency may be possible in future breeding programs.