Rootstock effect on water consumption in pear 'Abbé Fetel'

The aim of this study was to investigate the effect of Malling H and Sydo quince rootstocks on water consumption and leaf performance of 'Abbé Fetel' pear subjected to different degrees of water restriction (restitution of 100, 50, 25, 0% of the recommended Etc). Leaves of fully irrigated trees grafted on the 2 rootstocks showed the same net photosynthesis with similar stem water potential. When irrigated with 50% of recommended Etc the bulk soil water potential, represented by the pre-dawn stem water potential, was similar between the two rootstocks. Sydo then showed drastically reduced stem water potential, stomatal conductance and net photosynthesis, while a slight decrease was observed for leaves of trees grafted on MH, resulting in better performance than on Sydo. This different behaviour in managing water may suggest the higher "optimistic" attitude imposed by MH that allow leaves to maintain a high stomatal conductance and photo-assimilation even at moderate water stress. At the severe water stress condition (25 and 0% of recommended water restitution) stem water potential, stomatal conductance and leaf net photosynthesis decreased similarly in both the rootstock treatments. Tree productivity was also affected by rootstock used and the water volume supplied. The highest commercial productivity (fruit diameter >65 mm) was reached by MH followed by SY, both fully irrigated. Supplied with 50% of the recommended water volume, commercial productivity was reduced by 17 and 38% of fully irrigated treatments in MH and Sydo respectively. At 25% of the recommended water volume, commercial productivity decreased by about 70 and 90% of fully watered treatments in MH and Sydo, respectively. These preliminary results suggest the importance of the correct choice of rootstocks for the better management of water in the orchards. Further research on the effect of progressive water stress is needed