Grafting of fresh cuttings using drought-susceptible and low-yielding clones as scions on drought-tolerant clones as rootstocks offers the possibility of raising composite plants with improved productivity and drought tolerance. Hence, the study was aimed to widen the choice of compatible composites and to delineate the underlying factors responsible for productivity and drought tolerance in grafted plants. One year-old composite plants of TRF-1, TRF-2 and UPASI-28 cleft-grafted on the rootstocks of UPASI-2, UPASI-9, ATK-1 and TRI-2025 were field planted along with their respective controls and evaluated. The results indicated that productivity and drought tolerance of scion clones varied significantly with the rootstocks used. Significant increases in yield and yield components were noted in the following graft combinations compared with their corresponding self-rooted scion clones: TRF-1 grafted on UPASI-9 and ATK-1, TRF-2 grafted on all four rootstocks, and UPASI-28 grafted on UPASI-9, TRI-2025 and UPASI-2. The findings clearly emphasize the scion–rootstock interaction as the critical determinant of productivity in grafted plants compared with vigour, drought tolerance and yield potential of scion and rootstock clones. Further, high-yielding capacity of grafts over the ungrafted scions and rootstocks was largely dependent on the yield potential of the scion clone and the degree of scion–rootstock compatibility. Higher field survival and enhanced yield observed during the drought period in the compatible grafts demonstrated their better drought tolerance compared with their respective self-rooted scions.

Introduction. ‘Orange Red’ is an apricot cultivar released in the United States and characterised by large fruit of very good quality for both the fresh market and processing. For this reason, this cultivar is greatly appreciated in Europe, especially in France. However, its production is erratic under Mediterranean climate conditions. Materials and methods. The influence of two rootstocks (‘Manicot’ apricot and ‘GF31’ Myrobolan plum) on the productive behaviour of ‘Orange Red’ was studied under Mediterranean conditions in Murcia (Southeast Spain). Results and discussion. ‘Orange Red’ grafted onto ‘GF31’ Myrobolan flowered slightly later than those grafted onto ‘Manicot’ apricot. However, differences in the date of ripening of fruits were small. On the other hand, the percentage of flower bud retention and levels of floral fertility were higher when ‘Orange Red’ was grafted onto ‘GF31’ than onto ‘Manicot’, resulting in higher yields and fruits with a smaller weight. The increase in flower bud retention of ‘Orange Red’ grafted onto the rootstock ‘GF31’ was the main factor responsible for the increase in yield observed with this rootstock. Conclusion. Interaction between the cultivar and rootstock is presented as an interesting strategy for cultivar adaptation to different climatic areas.