Abstract: The double recessive nuclear male-terile line ms₅ms₆ of upland cotton (Gossypium hirsutum L.) has been widely used in a large-cale. However, the structural basis of anther abortion in cytology of this material is still unknown. Transmission electron microscopy was used to observe nuclear male-terile line ms₅ms₆ in stages of tetrads and microspores on which there are small spinescent protuberances. The results show that the male-terile microspores have only endexine during the stage of microspore, however, the fertile microspores have sexine and endexine of cell walls. In the microspores and tapetum cells, the abnormal endoplasmic reticulum and no fat accumulation were found during male sterile anther development, which might be the most important reason of microspores abortion.

Key words: upland cotton, ultrastructure, anther, nuclear male sterile line, tapetum