Two partially male sterile plants were identified in the widely cultivated rape variety Zhong You 82 in Guizhou during 1989 and designated H90S. Test crosses, sib-mating, selfing and shuttle breeding performed at different locations during 1990-94 indicated that fertility in H90S is controlled by recessive gene(s) which are different from those previously identified in 117A or S45A. The percentage of sterile H90S plants was increased from 15 to 96% through 9 generations of selection. In 1994, H90S was sown at 16 different dates from 20 July to 30 December. Results showed that expression of male sterility was influenced by light duration during floral differentiation, and accumulated temperature to floral differentiation and first anthesis.