Fruit set after self-pollination at different floral stages and its relation to pollen-tube growth and stylar S-RNase content in Japanese apricot (Prunus mume Sieb. et Zucc.).

摘要

To investigate fruit set after self-pollination at different floral stages, and its relationship to the S-RNase content of the style in Japanese apricot, which exhibits gametophytic self-incompatibility (GSI), the cultivar 'Xiyeqing' was selfand cross-pollinated at -6, -4, -2, 0 and +2 d after anthesis (DAA). At -6 and -4 DAA, the percentage fruit set was low, suggesting that the propensity to seed set was weak during this period. At -2 DAA, the percentage fruit set, after self-pollination, reached a maximum of 5.97%. Thus, the effective time of self-pollination to obtain inbred seed was -2 DAA. Soluble protein extracts of styles at each floral stage were subjected to iso-electric focussing. The results showed that S-RNase began to be synthesized from -6 DAA, reached its maximum expression 2-3 d before anthesis, and was degraded slowly after anthesis. The number of pollen-tubes arriving at the stylar base, as detected by fluorescence microscopy, varied at -2, 0, and +2 DAA. The number of pollen-tubes arriving at the stylar base, and the percentage fruit set after self-pollination, exhibited a positive correlation (r=0.8615; P=0.1), while the S-RNase content per style showed a negative relationship to fruit set percentage (r=-0.9640; P=0.01), and to the number of pollen tubes arriving at the stylar base (r=-0.9380; P=0.01) during this period. This implied that the S-RNase content in the style was mainly responsible for the low percentage fruit set and the low number of pollen-tubes arriving at the stylar base after self-pollination.