Analysis On Combining Ability And F₁’s Temperature Sensitivity Of New Male Sterile Lines And New Restorer Lines Of Indica Rice

This paper focuses on the combining ability of their main agronomic and quality traits and their application potential in breeding in resistance to temperature stress between new male sterile lines and new restorer lines of indica hybrid rice. Four self-bred new male sterile lines(G Ruanhua A, G Huazheng A, N11 S, N727S) and four new restorer lines(Huagandao 3, Huahui 55, Huahui 521, Huahui 271) were combined, then the combinations and restorer lines were planted by stages. Main agronomic and quality traits of those combinations and restorer lines were studied to analyze their combining ability and temperature sensitivity. The following results were obtained.1. In agronomic traits, while general combining ability variance and specific combining ability variance were significant at 5% or 1% levels for most traits, the former was larger than the later. The contribution rates of general combining ability variance of male sterile lines were much greater than those of restorer lines regarding panicles per plant, seed setting rate and seed weight per plant. However, in regard to panicle length, number of grains per panicle, number of filled grains per panicle and 1000-grain weight, those rates of restorer lines were greater. Among the male sterile lines, N727S’s general combining ability performance of seed weight per plant was the best, and the yield components were more coordinated, but the plant height was higher and the agronomic characters were not fully coordinated. Thus, extra attention should be paid to the lodging resistance when N727 S is used to combine some restorer lines. The situation of Huahui 55 in restorer lines was similar to that of N727 S in male sterile lines.2. In quality traits, while general combining ability variance and specific combining ability variance were significant at 5% or 1% levels for most traits, the former was larger than the later. The contribution rates of general combining ability variance of male sterile lines were much greater than those of restorer lines regarding brown rice rate, head rice rate, grain length, grain width, chalky rice rate, chalkiness degree and amylose content, while as regards milled rice ratio, length/width ratio and gel consistency, the rates of restorer lines were greater. Among the male sterile lines, G Ruanhua A was superior and had no obvious defects. Among the restorer lines, Huagandao 3 showed desired traits in brown rice rate, chalky rice rate, chalkiness degree and length/width ratio. Huahui 521 had desired traits in milled rice ratio, head rice rate, amylose content and gel consistency.3. The combining ability variance analysis of temperature-sensitive index showed that general combining variance contribution rates of restorer lines were greater, which indicates that the improvement to temperature stress resistance should be made mainly in restorer lines. The correlation analysis showed that temperature-sensitive indexes of sowing dates in May and August were significantly correlative at 5%. It also showed that sensitivity strength in low and high temperature was significantly correlative at 1%, which implied that low- and high- temperature sensitivity of rice was correlated. The combinations and restorer lines were divided into four categories in the cluster analysis based on temperature-sensitive index, among which number 7, 8, 10 and 20 in the second category featured smaller temperature- sensitive indexes. Additive main effects and multiplicative interaction(AMMI) model was applied to analyze the stability of temperature sensitivity. Then is was found that the combinations of male sterile line N727 S, restorer line Huahui 55 and restorer line Huahui 521 had lower temperature sensibility and higher stability. And the analysis of temperature sensitivity periods showed that the sensitive periods ranged mainly from the day before heading to the second day after heading.4. Among the male sterile lines, N11S’s combinations featured moderate temperature-sensitive periods and relatively strong ability of resisting high temperature stress. In the restorer lines, Huahui 55’s combinations had moderate temperature-sensitive periods and usual ability of resisting low temperature, while their ability of resisting higher temperature was relatively greater, and temperature sensitivity was greater than that of restorer lines themselves. As for Huahui 271’s combinations, they were of shorter temperature-sensitive periods, usual abilities of resisting lower and higher temperatures, and greater temperature sensitivity than restorer lines themselves.A conclusion was drawn based on the above results. Major agronomic and quality traits are controlled by both additive and non-additive effects, and additive effect plays a principal role. Male sterile line N727 S and restorer line Huahui 55 are suitable for the improvement of agronomic traits, while male sterile line G Ruanhua A is suitable for the improvement of quality traits. The improvement of rice’s ability of resisting temperature stress should focus on restorer lines. Temperature sensitivity is correlated between low and high temperature. Male sterile lines N11 S and restorer line Huahui 55 are suitable for the improvement of temperature-sensitive trait.