| Female sterility widely existed in plantae. The first report of plant female sterility appeared in the 1950s. Nowadays, the female sterility produced by crossing of indica and japonica was extensively studied in rice. And most of them belonged to structural infertility caused by embryo sac developing abnormally. The mutant materials of this experiment came from Shuhui 202 ( an indica restorer) .Its plant type was normal and it could flower normally. However, the rate of seed setting was less than 1%. The main experiment included identifying the pollen fertility, the rate of seed setting of crossing, reversed crossing and mixed - pollinating of multi-male-parents, investigating the mature embryo sac , the fertilization and the developing of the embryo and the endosperm. Genetic analysis was carried out and the mutant gene was preliminarily mapped by using SSR markers. The results are as follows:1. Observing of exterior shape: There were six anthers and two stigmas like feather. It has one ovary with normal shape. The pollen fertility rate was above 90%. It indicated that the pollen fertility was normal.2. Using the mutant as male parent crossed with Shuihui-202, 9311, D62B, G46B, 527R, respectively. Their seed setting rate all exceeded 30%. Nevertheless, the rate of seed setting by reversed crossing and mixed-pollinating all were zero, and by self-pollinating was less than 1%. The result further indicated that the maleness of mutant was absolutely fertile and its sterility was determined by the femaleness.3. Investigating the sensitivity to the illumination and temperature : It was found that the seed setting rate of the mutant had no apparent change in different time .It indicated that the illumination and temperature had no influence on the sterility of the mutant.4. Observing the mature embryo sac of the mutant: It was found thatthe embyo sac appeared in typical polygonum type and more than 90% of the embryo sac hadintegral inner structure. They had egg apparatus (an egg cell and two synergids), two polar nucleus and three antipodal cells , and their position in the embryonic sac was normal . The development of male and female organs was in-phase. Therefore, the embryo sac structure of mutant was normal.5. Investigating pollination, fertilizing and embryo developing course: Pollen grain began to germinate after flowering 3-5min, then to elongate. However, it stopped in the pistil and couldn' t arrive in ovary. In embryo sac, .sperm couldn' t be observed in every stage after flowering. Most of the ovaries(about 70%) expanded after flowering a few days. But the embryo and endosperm couldn' t be found. On the contrary, the unfertilized egg cell and polar nuclei could be observed. It indicated that the reason of infertility of the mutant was the unfinished double fertilization caused by the blocking of elongation of pollen tube.6. Fertility investigating in field and genetic analysis: The F, progency of the mutant crossed with 1023A and G46A were absolutely fertile. Investigating for F2 population showed that the segregation ratio of nomal plants and mutant plants fit a ratio of 3:1 .It indicated that the female sterility trait was controlled by single recessive genes.7. Analyzed by SSR markers: Using 512 pairs rice SSR markers to analyze the mutant , 1023A and F2 population , it indicated that RM17 located in NO. 12 chromosome was linked with aimed gene and their genetic distance was 4.03 cM. |
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