Rootstock and water restriction effects on leaf performance and fruit growth in pear, cv. 'Abbé fetel', grafted on different quince rootstocks

The availability of high quality water resources is becoming increasingly limited, and has been identified as a global problem. Agriculture must learn to operate under water scarcity, where insufficient supply will be the norm rather than the exception, developing more efficient water management practices that enable production under a limited supply. Under water restriction stomatal limitation reduces leaf photosynthesis. To compensate for energy imbalance, alternative electron pathways become increasingly active. These pathways reduce the photodamage risk while consuming energy and CO2 (e.g., photorespiration). For tree crops one agronomic strategy to cope with drought is to use water stress tolerant rootstocks. The aim of this study was to evaluate three pear rootstocks subjected to water restriction. Leaf performance and tree productivity were evaluated on ‘Abbé Fetel’ pears grafted on three different quince rootstocks (Adams, MH and Sydo), fully watered or irrigated with 50% of the recommended dosage. During the end of fruit cell division stage, leaf photosynthesis, stomatal conductance, and the alternative electron transports were unaffected by water restriction. However, differences were recorded between the three rootstocks. MH showed the highest values of leaf photosynthesis but was less stomatal limited. During the following stage of fruit cell expansion the interaction between rootstocks and water treatment was significant. Water restriction was more effective in the Sydo rootstock, which reduced photosynthesis and stomatal conductance, increasing the activity of the alternative electron transports. This behaviour was reflected in fruit productivity, which was reduced in Sydo under water stress. These results suggest the possibility to improve irrigation management in pear via a better understanding of plant behaviour at leaf and fruit level during its vegetative season, in combination with the choice of the most appropriate rootstock.