Growth and Productive Behavior of 'Doyenné Du Comice' Pear Trees Grown on Two Rootstocks and Two Water Regimes

The effects of rootstocks and water supply on growth and productive behavior of pear trees were evaluated during the growing season of 2003. The experiment was carried out in the experimental area of the Dipartimento di Coltivazione and Difese Delle Specie Legnose, Universita degli Studi di Pisa, Italy. Nine-year old trees of the cv. Doyenne Du Comice were used, grafted either on pear (Pyrus communis) or quince (Cydonia oblonga Mill.) rootstocks and grown under two different water regimes, irrigated or non-irrigated. The fruit growth curves, water xylematic potential, trunk diameter fluctuation, leaf temperature, gaseous exchanges, soil moisture content and estimated yield were analysed during the fruit growing period. The fruit development presented a standard simple sigmoidal curve. Irrigated trees produced larger fruits, where the most significant period was the final fruit growth stage. Irrigation also induced greater fluctuation of the trunk diameter and low leaf temperature, even after 35 days of water removal. Trees grafted on irrigated quince rootstocks exhibited higher gaseous exchanges, as well as estimated yields. The results indicated that water stress can influence the growth and productive characteristics of pear trees. The quince rootstocks showed more sensitivity to water stress than Pyrus ssp. rootstocks.