Study On The Performance Of Sterility Differences For The Population Of Thermo-Sensitive Genic Male Sterile Rice Lines

To explore the methods of studying the differences of the fertility performanceandthe distribution rule between the individulswithin thermo-sensitive genie male sterile rice, and summarize the quantitative indicators which could describe these differences and distribution rule, we made a research on the varalites of the fertility performance and distribution law within the group of some thermo-sensitive genie male sterile rice having the different starting point temperature, and different generation of the same variety and the same group under different environmental temperature, and then measure the starting point temperature of sterility, fertility characteristics including stability and consistency with a series of quantitative indicators. Five typical representative sterile lines including ZhunS, P88S, Y58S, Guangzhan63-2S, Guangzhan63-4S, widely used in rice production in china, were selected to carry out a series of experiments, because of the greater differences in growth period length, starting temperature, resistance and uniformity between them. The elite stock seeds of ZhunS, P88S and Guangzhan63-4S were produced through the core seed breeding generation; The stock seeds of Guangzhan63-2S were obtained through the core seed production procedure, and then seven sterility core individuals were selected out on the basis of stock seeds; The stock seeds of Y58S were propagated through the core seed production procedure, and the one generation of stock seeds were further obtained. When the selected materials were in a fertility sensitive period, the individuals of each material were sampled and treated for 6d with cold water whose temperature was maintained for 22.5?, and then the pollen fertility was detected under a microscope after treatment for 17 d. The results of microscopic examination were analyzed and displayed as follows:1 It is an effective method of studying the fertility differences of population of Thermo-sensitive genie male sterile line that the sterility of pollen was detected on the twelfths days after treatment for 6 days with constant temperature water at 22.5?. Five quantitative indexes including the amplitude of dyed pollen rate, the average rate of pollen, the rate of complete sterile pollen, plant peak rate, and dyed pollen rate with plant peak rate were stable, and can accurately reflect fertility characteristics of sterile line having different starting point temperature, and had strong repeatability and high stability.2 After four sterile lines Y58S, Guangzhan63-2S, Guangzhan63-4S and P88S were treated for 6 days with constant low temperature water at 22.5?, the sterility of pollen was examined under a microcopy, and the results showed that (1) because the starting point temperature of sterile lines was different, the dyed rate of pollen of sterile lines was obvious different between them; according to the results of average pollen rate of dyeing, the amplitude of dyed pollen rate and complete sterile pollen rate, among four sterile lines, Y58S had the lowest sterile starting point temperature, and Guangzhan63-4S, P88S had the highest sterile starting point temperature; (2) dyed pollen rate (i.e., sterility stability) was greatly different among different sterile lines at pollen sterility fluctuation period; based on the results of plant rate peak, Guangzhan63-2S had good fertile stability, and P88S had poor fertile stability, and Y58S, Guangzhan63-4S had medium fertile stability.3 The minor genes is the main genetic factors leading to genetic drift of sterile starting point temperature of thermo-sensitive genie male sterile lines, and their numbers and homozygous condition deeply affected the beginning temperature and sterile stability of sterile lines. In this study, the results indicated that the populations of first generation of seven complete sterile individuals derived from the stock seed population of Guangzhan63-2S had obvious differences in fertility performance. On the basis of results of the amplitude of dyed pollen rate and plant rate peak, the starting point temperature was significantly different, among them one plant was higher, two plants were lower and the others was medium. Thus, the core individuals were selected out by microcopic examination, but the fertile stability of the first generation populatons of every core individual was different. That is to say, the fertile performance difference between individuals could only be weakened, but not eliminated, which further confirmed that the seeds of sterile lines within three generations from the core seeds were only utilized in hybrid rice seed production to make sure seed production safety.After the populations of Y58S'stock seed and its first generation were treated with constant low cold water, the fertility of populations was different. According to the results of the amplitude of dyed pollen rate, average dyed pollen rate, complete sterile plant rate and plant rate peak, we can see that the starting point temperature of stock seed was lower than that of the first generation, and the fertile stability of stock seed was higher than that of he first generation, the propagation conditions of sterile lines had a great influence on the amplitude of temperature drift, and the higher the temperature at propagation period was, the larger the amplitude of starting point temperature was.4 The populations of Thermo-sensitive genie male sterile lines was all sterile at sterile periods, and their fertile performances was unanimous, but the same populations had a great differences in fertile performance at fertile fluctuation period and fertile initial stage. In this study, the results showed the fertile performance difference of Y58S between individuals was very great at at fertile fluctuation period and fertile initial stage. The fertility of population was vaguely described as a single value in previous studies, and we thought it was not comprehensive, because it ignored the general distribution of fertile instability between individuals within populations. The results also indicated that five quantization indexes including the amplitude of dyed pollen rate, average dyed pollen rate, complete sterile plant rate, plant rate peak an its corresponding dyed pollen rate could be used to accurately and unfairly measure the fertile performance differences. Among those indexes, the average dyed pollen rate and complete sterile plant rate were used to measure the difference of starting point temperature; the plant rate peak an its corresponding dyed pollen rate were utilized to describe the sterile stability of male sterile lines. Overall, these five indexes interrelate with each other, and none of them could be excluded.