Embryonic And Genetic Study On Twin-seedling In Rice

Twin seedlings are known to originate from one matured caryopsis. W3338 and W255 are twin seedlings rice (Oryza sativa L.) of heredity stability, identified from Rice Research Institute of Sichuan Agricultural University. R527, 9311 , Nippbare and Zhonghua15 are conventional cultivars with no twin seedling trait. It was no further reports about W3338 and W255, but the effects on selection on them and the initial study on their cytoembryology by Luoming. The object of this reseach is: elucidating morphologic essence and forming type and genetic characteristics in twin seedlings, through embryonic and genetic study. The results show below:1. The result of embryonic observation in W3338. The total of embryo sac are 374, the embryo sac of W3338 was typical polygonum type. Only one egg cell in the each of 313 observed embryo sacs before fertilized, 0.27% of 313 florets contained one fuse-double ovary developed normally, other 0.27% of 313 embryo sacs before fertilized present abnormally, existing 3 similar egg cells around the polar nucleolus. 61 embryo sacs after fertilized were normal.2. The result of embryonic observation in W255. A total of 1275 ovaries before and after the day of anthesis were observed, the embryo sac was typical polygonum type, and 0.08% of 1275 ovaries contained double ovules and fuse-double ovary. Each of 879 ovaries before fertilized contained only a single embryo sac with a set of normal egg apparatus. The variation in the position and amount of antipodal cells before as well as after fertilization in W255 was also investigated.3. On germinating and integral dissection in the two successive progenies of twin seedling rice, W3338 and W255, twin seedlings generated from the posterity of mono-seedling and poly-seedlings. Except for lowest frequency of independent twin embryo seedling, others were twin seedling with one radicle. Further more, the single, twin...