Studies On The Difference Of Seed Setting Rate And Its Correlation With Temperature About Single Cropping Hybrid Rice In Dongting Lake Area

18 single cropping hybrid rice combinations in Dongting Lake Area were selected to serve as experiment materials, which cultivated in this area for many years and performed well, and reduced yielding because of the abnormally high and low temperature at one time, and approved and released by the Hunan Provincial Committee of Crop Variety Identification in recent years. Via seeding in different locations in different time, the difference of seed setting rate of the single cropping hybrid rice combinations in Dongting Lake Area and its correlation with the temperature before-and-after heading stage were analyzed by comparing averages, analysis of variance, correlation analysis; And the relationship between the heading and flowering stage temperature and seed setting rate of these provided combinations were analyzed by Simulation quadratic regression analysis. The main research results were as follows:1. The dynamic changes of seed setting rate of these provided combinations, which planted in the same location and the different seeding period, were relatively close to each other in Yiyang test points and Yueyang test points, and the seed setting rate in Yiyang test points and Yueyang test points was higher than Changde test points, the highest test point of seed setting rate was in Yiyang. The dynamic changes of seed setting rate which seeding in different period in Changde undulated enormously and differed greatly among combinations in the same seeding period; The dynamic changes of seed setting rate of the former 6 seeding periods in Yiyang test point and the former 4 seeding periods in Yueyang test point were fluctuated less, and the change trend similarly, smaller difference among combinations, and that of other seeding periods were the same as Changde test point. For most of the provided combinations, Yiyang is the best region to plant these combinations as single cropping rice in the Dongting Lake Area, Yueyang taking second place, and Changde the worst. The appropriate seeding period in Yiyang and Yueyang test points was April 20 to April 30, Changde test point was April 25 to May 5.2. The difference of average seed setting rate of 16 combinations in different locations reached 1% or 5% significance level except No.17 and No.18. Changde's average seed setting rate of 18 combinations was lowest. Seed setting rate of No.4 and No.12 were higher in Yueyang test point, and of other 16 combinations were higher in Yiyang. The average seed setting rate of No.12 was abnormal in 3 test points, even the highest test point (Yueyang) only had 73%, therefore, No.12 was unsuited to plant in all Dongting Lake Area as single cropping rice; in addition, the average seed setting rates ofNo.1,No.2,No.4,No.11,No.13 and No.16 were 72.1%,71.1%,68.9%72.6 %,71.4 % and 68.4 %, so we must be careful when extending these combinations in flat lake area of Changde as single cropping rice; No.2, No.9, No.10 and No.13 in Yueyang were the same as Changde should be careful when extending as single cropping rice.3. The difference of seed setting rates among different seeding periods of 11 provided combinations reached 1% or 5% significance level. In addition to No.10 and No.12, the seed setting rates of other 16 combinations were higher in first and third seeding period (above 80%), so for the most of provided combinations, sowing these combinations as single cropping rice in April 20 to April 30 was suited; the difference of seed setting rates of No.12 and No.13 didn't reach significant level, and there were 9 seeding periods with lower average seed setting rate (variational range were 74.4%—57.2% and 79.5%—67.6%), so this two combinations were unsuited to plant in Dongting Lake Area as single cropping rice.4. The results of correlation analysis for the seed setting rate and temperature in different growth periods of before-and-after initial heading stage showed that the highest temperature in a day was the head temperature factor making seed setting rate reduce. For most of the provided combinations, the sensitive period making seed setting rate reduce was the booting stage (before initial heading stage 5 to 15 days); the growth periods of No.4, No.6, No.10, No.12 and No.15, which affected seed setting rate by high temperature, were longer (from before initial heading 1-15 days to after initial heading 1-10 days or 1-15 days); For No.16, the temperature during 1-10 days after initial heading stage affected the seed setting rate little, but affected more during 10-15 days after initial heading stage (milk stage).5. In the test combinations of heading and blooming stage, there were 2 times of abnormal high temperature obviously occurred in Changde, one is from 22th July which lasted 13 days, the other is from August 8th to 11th which lasted 4 days. The maximum temperate of those days reached 35°C,daily mean temperate reached 30°C and daily minimum temperate was 25°C.setting rates of combinations which tasseled and bloomed in this period were subject to different impact, which reduced by 10-20% than normal temperate. For example, the seed setting rate of the 3rd sowing period of No.17 and the 6th sowing period of No.18 reduced by 11.3 and 19 percent point than former sowing period. Unusual cold weather (2-3days consecutive daily average temperate was below 22-23°C) has appeared once in 3 test point from Aug 15th-17th.At this time, seed setting rate of combinations which tasseled and bloomed altered, No.13 had a larger decline, the 7th sowing period in Changde point and the 5th sowing period in Yueyang point dropped 9.7 and 23.7 percent point respectively than former sowing period.6.The results of quadratic regression analysis for seed setting rate and temperature in heading and blooming stage showed, there were 11 combinations more sensitive to temperature in heading and blooming stage, and 7 combinations were insensitive; The two total quadratic regression analysis results of the daily highest temperature and setting rate in the heading and flowering time period of 18 and 11 provided combinations may be substituting respectively the simulation regression analysis results of the daily highest temperature and setting rate in the heading and flowering time period of the general types and the temperature-senstive types combinations of single cropping hybrid rice in the whole of Dongting Lake Area, regression equations are: Y =- 433.78+32.28X-0.5X~2 and Y =- 644 .74+45.56X -0.71X~2 (Y is the setting rate,X is the daily highest temperature), its seed setting rate to the value of the temperature dropped to 32.04 and 32.01°C respectively.