Genetic Variation And Utilization Evaluation Of Yield And Quality Traits In Different Generations Of Dian-type Hybrid Japonica Rice

Hybrid rice varieties prepared by“three-line method”have been widely used in production in China and have achieved significant yield increase.However,because this hybrid variety can only be planted once,it is necessary to produce seeds every year,which is not only cumbersome,but also the current seed production yield is not stable enough,and the cost of seed production is expensive,which limits the development of hybrid rice.Farmers buy seeds every year,the production input is high,but the economic benefit is not high.Therefore,the multi-generational utilization of hybrid varieties has gradually become a topic of concern.In Yunnan rice production,we found that in order to save seed costs,some local farmers continued to plant the seeds of F₂and other separated offspring of high-quality Dian-type hybrid japonica rice as self-reserved seeds.Although the field population was not neat,the farmers were still satisfied with their yield and quality.However,there is no systematic research on the multi-generation utilization of Dian-type hybrid japonica rice,so it needs further discussion and research.In this study,Dian-type three-line hybrid japonica rice varieties“Dianheyou 61”,“Dianheyou 615”and“Dianheyou801”with high quality,wide adaptability and strong disease resistance were selected as materials for continuous self-crossing of large populations,and self-crossing populations of different generations from F₁to F₄were constructed respectively.The agronomic traits（plant height,number of effective panicles,panicle length,number of grains per panicle,number of filled grains per panicle,etc.）of each cross population were investigated.The yield and rice quality indexes of different generations of self-crossing populations were measured.By comparing their genetic differences,the feasibility of multi-generation utilization of Dian-type hybrid japonica rice varieties was analyzed.In order to solve the problem of high production cost and low economic benefit of farmers,and lay a theoretical foundation for solving the“seed bottleneck”problem restricting the development of Dian-type hybrid japonica rice and subsequent related research.The main results are as follows:1.Dian-type hybrid japonica rice varieties in different generations have a wide range of genetic variation and rich genetic diversity,its yield,filled grain number,effective panicle number and other agronomic traits of the coefficient of variation is large,in the breeding process of rice varieties is an important measure,can be used as a basis for the distinction between good varieties;the main agronomic traits have a high diversity index,indicating that the offspring of hybrid rice have rich genetic diversity,which can be used as a germplasm resource pool to provide material support for the breeding of high-quality varieties.2.In terms of yield,the yield of F₁generation of“Dianheyou 61”was significantly higher than that of F₂and F₄generations,and there was no significant difference with F₃generation.The yield of F₁generation of“Dianheyou 615”and“Dianheyou 801”was significantly higher than that of F₂,F₃and F₄generations.There was no significant difference in the yield of F₂,F₃and F₄generations of the three varieties.Except for“Dianheyou 615”（F₄）,the yield was higher than the average rice yield（6.41 t/hm²）of Yunnan Province in 2020,providing direct use of space.3.In terms of quality,the changes of rice quality in each generation varied with different varieties.The comprehensive quality of“Dianheyou 615”（F₁）was better than that of other generations（F₁>F₃>F₄>F₂）,which decreased with the increase of generations,and the offspring were not conducive to direct utilization.However,“Dianheyou 61”and“Dianheyou 801”had better comprehensive quality in the high generation F₄（sorted as F₄>F₂>F₁>F₃,F₄>F₃>F₁>F₂,respectively）,which showed an upward trend with the increase of generation number,and their high generation could be directly used.The effects of different varieties on rice quality were as follows:main appearance quality>cooking and eating quality>main nutritional quality>milling quality.“Dianheyou 61”（F₄,F₂,F₁）was superior to other varieties in main appearance quality,“Dianheyou 615”（F₄,F₂,F₃）was superior to other varieties in milling quality,main nutritional quality and cooking and eating quality.