Studies On The Mechanism Of Cytoplasmic Male-sterility In Onion (Allum Cepa. L)

Onion is one of the most important vegetable crops in the world. The reported results show that onion possesse higher hybrid superiority. The selection of hybrid variety of first generation has become a main objective in onion breeding. Because of the small flower organ and the low seed-getting rate of single flower, the cost of the manpower castraction is high in onion hybrid seeds production. Using the male sterility line to confect the crossbreed seed is an efficient pathway. By using the technology of light microscopy, transmission electron microscopy, DNA ladder and the molecule mark of RAPD (Randomly Amplified Polymorphism DNA), the CMS of two male-sterile line 63A and 70 developed by the institute of Vegetable Crops of Jiangsu Academy of Agricultural Sciences was studied accidently. 1. The microstructural observations of the microspore and the anther wallâ‘  At the pollen-mother cell stage, the pollen-mother cells both in fertile anthers and sterile anthers could develope normally. But in the male sterile anther, pollen sacs were formed irregularly and the tapetum formation was incomplete at the pollen-mother cell stage.â‘¡At the tetrad stage, the pollen-mother cells in sterile and fertile anthers went through meiosis and formed normal tetrad while there were many differences between their middle layer and tapetum. In the fertile anther, the cell of the middle layer arranged in order and the nuclei of the tapetum and the middle layer were observed clearly. At the same time, the tapetum adhering to the endothecium developed completely possessing dense cytoplasm. 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.â‘¢At the microspore stage, although the tapetal cytoplasm degraded, the nuclei of the tapetum and the middle layer were observed clearly in fertile anther. However, the middle layer and the tapetum in the sterile anthers were degraded completely and...