Study On The Sterility Of F₁ Hybrids Between Indica And Japonica Rice

Rice is one of the most important crops in the world. It plays an important role in our country. But its yield per acre has pacing up and down for more than ten years. If we can't improve the yield drastically, we will face the danger of rice food in the 21 century. The FI hybrid between indica and japonica has great hybrid vigor in vegetative organ and yield trait. If we can use it directly, we may make a breakthrough in yield But we can't utilize it directly at present because of the low seed set that exists in them. So studing on the sterile mechanism of FI hybrid has an important sense of theory and practice.In order to analyze the cause of the highly spikelet sterility observed in the FI hybrid between Indica and Japonica, stamen and pistil were paraffin-sectioned at 8μm thickness and stained with Ehrlich's hematoxylin to observe the male and female development of F] hybrid. The adsorption and germination of pollens in the hybrids within and between Indica and Japonica F1 hybrids also be observed by scanning electron microscope. Meanwhile, pollen viability were observed with potassium iodide solution(l2-KI) and fluorescent diacetate acetone(FDA); the embryosac's fertility were examined by immersed with hydrochloric acid and stained with I2-KI. Results of the cytological studies of partial male and female sterility' in FI hybrids between subspecies crosses Nanjing11/Qiuguang, varietal crosses Nanjing11/IR36 were described as follows:1. Anther development was usually normal before tetrad stage. The partial pollen abortion in F1 hybrid of Nanjing 11/Qiuguang occurred after uni-nucleate stage(the microspore sterility was 20.27%). By contrast, Nanjing11/IR36 were normal from the beginning to the end(the microspore sterility only was 2.25%). In the development of macrospores in the subspecies hybrid, there were some embryosacs that there was no differentiation. Those embryosacs that could differentiate were normal in early stage, and could be divided into two nucleate stages in the first mitotic division, but many of them couldn't be divided in the second and the third mitotic division in the follow time. So itcan't format the normal embryosac-eight nucleate stage. The hybridization betweenvarieties was normal.2. The recognition between pollen grains and stigma in Nanjing 11/Qiuguang and Nanjing11/IR36's FO and FI were observed under scanning electron microscope. The results as follows: in F0 and F1. the adhension number between stigma and pollen insubspecies crosses were little than that in varieties crosses. It was 0.48 Entris/cm2 and 0.2 Entris/cm2 in Nanjing11/Qiuguang's FO and FI respectively, 3.5 Entris/cm2 and 3.62 Entris/cm2 in Nanjing11/IR36's F0 and F1 respectively Many of the pollen grains that attached to the stigma can sprout in general. But some of the spermary presented variant morpha in their elongation stage. Such as enlargement, curvifoum, twist and so much in the stigma's surface in the subspecies crosses. While the spermary of the varietal crosses was normal in their enlonged. This suggested that: the pollen and stigma in the subspecies hybrid has bad compatibility.3. The mature pollen fertility was observed by I2-KI stainability and FDA stainability. In Nanjing11/Qiuguang. the I2-KI stainability was 25%, the FDA stainability was 40%(I+II). While in Nanjing11/IR36. the I2-KI stainability was 80%, the FDA stainability was 80%(I+II). These indicates that both starch accumulation and dehydrogenase's force influencecd the setting percentage of F] hybrid indirectly.4. The embryosac's fertility was observed by immersed with hydrochloric acid and stained with I2-KI. In Nanjing 11/Qiuguang, the fertility of embryosac was 25%-30%, but it was 60%-90% in Nanjing 11/IR36. This indicates the low fertilized rate was the cause of the low seed set in the subspecies crosses.5. Comparison the pollen and embryosac's relative importance showed: the proportion of subspecies crosses' embryosac was 58.20%, pollen's was 41.80%; whereas varietal cross' embryosac was 53.47%, pollen's was...