Abstract: A photoperiod/thermo-sensitive male sterile line, named Huiyou50S, was developed from a spontaneous semi-sterile plant found in Brassica napus cultivar Huiyou50. The male sterility of Huiyou50S was controlled by recessive nuclear genes. Huiyou50S presents male sterile under high temperature and long photoperiod condition, and fertility under low temperature and short photoperiod. The cytological characters of pollen and the anther development of Huiyou50S at the different stages were compared with its near isogenic line Huiyou50F, which is the male fertile sibling, by techniques including semi-thin sections, scan electronic microscopy, pollen grains staining with aceto-carmine, and whole anther clearing with methyl salicylate. The result indicated that the anther development of Huiyou50S was similar to that of Huiyou50F from sporogenous cell, pollen mother cell, meiosis, to tetrad stage. At the uni-nucleate stage, although the exine formed, the protoplast of microspores condensed, and the cell became empty. At last all cellular content of pollen degraded completely and only the empty and distorted shell remained. The tapetum development of Huiyou50S was similar to that of Huiyou50F up to tetrad stage, but its tapetal cells rapidly disintegrated at the uni-nucleate stage, which occurred earlier than that in Huiyou50F, while the tapetum of Huiyou50F did not degenerate at this stage. In conclusion, the microspores of Huiyou50S abort mainly at the uni-nucleate stage, and there are some associations between pollen abortion and tapetal cells’ disintegration. This result is helpful to classification and utility of photoperiod/thermo-sensitive genic male sterility

Key words: Brassica napus, Photoperiod/thermo sensitive genic male, sterility, Pollen abortion, Microspore, Cytology