Abstract:

Cytological studies of cytoplasmic male-sterility (CMS) mechanism have been reported in several crops of Arabidopsis, soybean, rice, wheat etc. To date no report on CMS studies in onion (Allium cepa L.) is available in China. By using the technology of light microscopy and transmission electron microscopy, microstructural and ultrastructural observations of male-sterility line 63A and maintainer line 63B anthers were done during their development in onion (Allium cepa L.). The results indicated that in the male sterile anther, pollen sacs were formed irregularly and the tapetum formation was incomplete at the pollen-mother cell stage. The middle layer was degenerated completely and collapsed into a thin layer, the tapetal cells become vacuolated and dissociated from the pollen sac wall, followed by condensation of the tapetal cytoplasm at the tetrad stage. Meanwhile, it was presumed that the tapetal cells in male sterile anther underwent premature programmed cell death (PCD) based on the DNA ladder. At the developing microspore stage, the complete disintegration of cytoplasm in the microspore was observed. It is suggested that the microspore abortion in male-sterile anther would be attributed to premature degeneration of middle layer and tapetum.

Key words: Allium cepa L., Abortion, Cytoloplasmic male-sterility, Cytology, Microspores