The use of drought-tolerant rootstocks is one of the available solutions for the cultivation of pear in semi-arid areas. In order to achieve drought-tolerant rootstocks, seeds of Pyrus syriaca, and Pyrus salicifolia species as well as Pyrus communis cv. Spadona, Khoj no. 1 and Khoj no. 2 were cultivated in the field conditions. This research was carried out as a factorial experiment with two factors of pear species (in five levels) and water stress (in two levels of control and drought stress) based on a randomized complete block design. In drought treatment, the irrigation time was considered based on 80% of allowed water depletion. In control blocks, normal irrigation was performed. The experiment began in July and continued to late September. In stress conditions, P. communis cv. Spadona and Khoj no. 1 had the highest seedling height and stem diameter and P. salicifolia and P. communis cv. Khoj no. 2 had the lowest of the rate of these traits. The lowest increase in electrolyte leakage (EL) and the highest proline content were in P. communis cv. Khoj no. 2 and P. salicifolia and the highest EL and the lowest proline were observed in P. communis cv. Spadonain under drought stress conditions. The most and the least relative water content (RWC) were belonged to P. communis cv. Khoj no. 2 and Spadona, respectively, in stress conditions. According to the studied traits, P. salicifolia and P. communis cv. Khoj no. 2 populations were more tolerant to drought stress.

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The cultivated pear is an economically important fruit tree species of genus Pyrus in which often gametophytic self-incompatibility occurs. Therefore, this species need to be pollinated by cross-compatible cultivars that bloom in the same time. Selection of appropriate pollinizers for pear cultivars is very important to produce commercial yield. 'Sebri', ' Shahmiveh' and 'Natanzi' are the best commercial cultivars in Iran, but the lack of a suitable source of pollen can reduce productivity. In order to select the most suitable pollinizer for these pear cvs, an experiment was conducted in which they were considered as pollen recipients and 'Coscia', 'Bartlett' and 'Sardroud' along with 'Sebri', 'Shahmiveh' and 'Natanzi' were evaluated as pollen donors. This research was conducted as a factorial experiment in randomized complete block design for four years. Recipient and donor cultivars had almost overlapping flowering time. The flower buds on selected branches were emasculated at balloon stage and then were counted and isolated with cotton tissue bags. Pollen grains of these pollinizers were collected in the laboratory. Isolation bags were taken off from the branches and emasculated flowers were pollinated with pollen grains of listed pollinizers during receptibility of stigma. The number of pollinated flowers was counted, and branches were covered again with the bags. The results showed that for 'Sebri' the best pollinizer was 'Coscia' with 5.7% fruit set, for 'Shahmiveh' 'Bartlett' cv. with 5.8% of fruit set and for 'Natanzi', 'Shahmiveh' with 5.5% of fruit set.

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