EVALUATION OF WATER-USE EFFICIENCY IN PEACH GRAFTED ON DIFFERENT INTERSPECIFIC HYBRID ROOTSTOCKS

Carbon isotope discrimination (DELTA) has been indicated as a method o f selection for improved intrinsic water-use efficiency (WUE) or produ ctivity in many C3 crop species. Improvement of WUE has not been succe ssful because evolution for this component of drought resistance is di fficult and unreliable in field-grown plants by weighing. This study w as conducted to assess and evaluate variability in DELTA and WUE among different interspecific hybrid rootstock (IHR) obtained from Prunus d avidiana x Prunus persica hybridization and in the combinations of the se IHRs with cv. Springcrest scion grown in non irrigated conditions. Comparison between WUE, plant productivity and plant vigour were analy zed; gas exchange properties and leaf characteristics were also examin ed and discussed. A great variability in DELTA was obtained in both IH Rs and in the scions analyzed. Positive correlations between WUE and y ield and WUE and vigour were also revealed in die combinations evaluat ed. No significative differences were found in leaf photosynthetic rat e and in leaf properties (average leaf area, specific leaf weight, nit rogen content and chlorophyll concentration), whereas the most vigorou s combinations transpired less and presented less sodium concentration in the leaf. These results indicate that the combinations more favour able, with higher values of WUE and yield, used the soil water more ef ficiently by delaying drought with a reduced transpiration without mod ifying the photosynthetic rate. The validity of P. davidiana x P. pers ica hybridization in order to create variability exploiting in peach b reeding was confirmed. The root signals theory on stomatal reopering r egulation seems therefore supported in evidence.