Influence of rootstock on pistachio (Pistacia vera L. cv Kerman) water relations

Selecting the rootstock in pistachio orchards is one of the most critical decisions, mainly in conditions of water scarcity. However, there are a few works that report the response of pistachio to water stress according to rootstock. Nowadays, UCB-I is one of the most important rootstock around the world. However, its commercial availability and high prices favour the selection of Pistacia terebinthus L. or Pistacia atlantica Desf. in some regions. The aim of this work is to study the water relations of these three rootstocks using cv Kerman as scion. Thirty pots, in the second year after budding, were subjected to a 28-days water stress period in outdoor conditions. Irrigation was stopped in the water stress treatments during all the 28 days period. The vegetative response was characterised at the end of the experiment. The diameter of the rootstock and scion, number of leaves and the percentage of leaves, trunk and root were measured. Along the experiment water relations parameters such as midday water potential and midday leaf conductance was measured. In order to compare the effect of rootstock and water stress pressure-volume curves were measured before and after the water stress period. Data of vegetative growth suggest that UCB-I was the rootstock less affected for water stress, because these data were not clearly affected. However, water relations parameters suggest that P. atlantica was the most resistant to water stress conditions, according to the results derivate from the pressure-volume curves. Possible mechanisms of response to water stress are discussed.