Effect of rootstock on trunk growth and foliar mineral content in cv. Bianca pistachio (Pistacia vera L.) trees

Trunk cross-sectional area (TCSA) and mineral content were recorded for 4 years in the major Sicilian pistachio cultivar, Bianca, budded in 1991 onto eight in v/fro-propagated clonal rootstocks (Pistacia atlantica and P. integerrima) and one seedling rootstock (P. terebinthus). The trees were grown using standard cultural practices for Sicilian dry-land farming in a fine sandy soil, located inland in Sicily (20 km SW of Palermo, 350 m a.s.l.). From nine trees per rootstock, samples of 10 leaflets from the mid-section of current year shoots were taken yearly in August and analyzed for the main plant mineral elements (N, P, K, Ca, Mg, Fe, Mn, Zn, Cu and B). The TCSA was measured at the end of each growing season. Clones of P. integerrima, especially clone 2, proved to be the most vigorous among the tested rootstocks, with a TCSA more than three times that of P. terebinthus. Clones of P. atlantica were of intermediate vigor, but differences in TCSA among the rootstocks tended to disappear in the last year of observation. There were no particular significant differences in the foliar concentrations of N, P, Fe, Mn and Zn, whereas there were significant differences among the rootstocks for Mg and K. Clone 3 of P. atlantica was the most efficient in using Mg and P. terebinthus in using K. Finally, an antagonistic effect was detected between these last two elements, with a highly significant negative correlation between K and Mg.