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

Carbon isotope discrimination (DELTA) has been indicated as a method of selection for improved intrinsic water-use efficiency (WUE) or productivity in many C3 crop species. Improvement of WUE has not been successful because evolution for this component of drought resistance is difficult and unreliable in field-grown plants by weighing. This study was conducted to assess and evaluate variability in DELTA and WUE among different interspecific hybrid rootstock (IHR) obtained from Prunus davidiana x Prunus persica hybridization and in the combinations of these IHRs with cv. Springcrest scion grown in non irrigated conditions. Comparison between WUE, plant productivity and plant vigour were analyzed; gas exchange properties and leaf characteristics were also examined and discussed. A great variability in DELTA was obtained in both IHRs and in the scions analyzed. Positive correlations between WUE and yield and WUE and vigour were also revealed in die combinations evaluated. No significative differences were found in leaf photosynthetic rate and in leaf properties (average leaf area, specific leaf weight, nitrogen content and chlorophyll concentration), whereas the most vigorous combinations transpired less and presented less sodium concentration in the leaf. These results indicate that the combinations more favourable, with higher values of WUE and yield, used the soil water more efficiently by delaying drought with a reduced transpiration without modifying the photosynthetic rate. The validity of P. davidiana x P. persica hybridization in order to create variability exploiting in peach breeding was confirmed. The root signals theory on stomatal reopering regulation seems therefore supported in evidence.