Preliminary study on the low self-fertility rate of 'Kuijin' apricots

To examine the self-sterility of apricots, pollen germination of ‘Kuijin’ apricot was conducted in vitro. Pollen viability was determined by germination on solid media. A comparison of the effects of different medium components on pollen germination and pollen tube growth revealed that the most suitable media for pollen germination and pollen tube growth were 10% sugar + 0.1% boric acid and 5% sugar + 0.01% boric acid, respectively. Comparison of four cultivars showed that, for pollen tube growth, the optimum sucrose concentration was 10% for ‘Katy’, ‘Jinkaite’ and ‘Golden Sun’ and only 5% for ’Kuijin’. The pollen germination rates of the four cultivars ranged from high to low in turn for ‘Katy’, ‘Jinkaite’, ‘Golden Sun’ and ‘Kuijin’, For pollen tube growth length, the order of the four cultivars from high to low was ‘Katy’, ‘Golden Sun’, ‘Jinkaite’ and ‘Kuijin’. The self-pollination rate of ‘Kuijin’ apricot, 4.7%, indicated that it is self-incompatible. Potential reasons for this self-incompatibility of ‘Kuijin’, including pollen weight and amount of pollen, were investigated. Both weight and amount of pollen were far less for ‘Katy’ than for ‘Kuijin’, but the self-pollination rate of ‘Katy’ is greater than that of ‘Kuijin’. The results showed that the self-pollination rate of ‘Kuijin’ is closely related to pollen tube length but had no direct correlation with pollen amount.