Study on compatibility and pollen tube growth of some Asian pear (Pyrus serotina Rehd.) cultivars

This experiment was conducted during the 2003 growing season to explore flowering and pollination aspects of some Asian pear cultivars introduced to Iran through Belgium by the Department of Horticultural Science (National Research project NO. 4225), Tarbiat Modarres University (TMU) in 1998. To study the flowering time and period, as well as the self- and cross-compatibility and incompatibility, nine Asian pear cultivars, including KS6, KS7, KS8, KS9, KS10, KS11, KS12, KS13 and KS14, were used. Two branches on each of four trees of each cultivar were selected for controlled pollination. To prevent unwanted pollen contamination and pollination by insects, selected shoots were protected with cotton tissue bags. For controlled cross-pollination, all flowers were emasculated and protected before anthesis, and hand pollination was carried out two days after anthesis. In order to monitor pollen tube growth in the style, samples were taken at 44, 72 and 96 hours after pollination and fixed in FAA solution. Preliminary results indicated that KS9 is a semi-self incompatible cultivar (fruit set = 2.92%). There were differences in the flowering period and time of bloom of the studied cultivars, although overlapping of flowering existed between some cultivars such as KS13 and KS11. Results based on the field and in vitro pollen tube growth tests indicated cross-compatibility between KS11, KS13 and KS8. Furthermore, preliminary observations of flowers showed differences in flower morphology in terms of shape and colour. There was a correlation between calyx and flower receptacle colour, and cultivars with brown fruit skin colour showed pigments in their calyx and receptacle in early fruit formation.