Studied On Genetic Variability Of Amylose Contein In Rice Grain And Its Selection Efficiency In The Late Generations Of Rice Progenies

Rice cooking and eating quality are important quality traits, and amylose content is one of the main factors which affected the cooking and eating quality, late hybrid generation is an important generation in which traits cause to separate and trend to sTableilization. Therefore, with regard to high quality and yield breeding, research on the genetic variability of amylose content in rice grain and its selection efficiency in the early generation of rice crosses was so important in theory and practice. In this experiment, two crosses–Xixuan 1×Tong 769, Dongnong 423×Fukei 180–were made using four Japonica rice parents with different amylose content, moreover, genetic variability and selection efficiency of amylose content were investigated in hybrid progenies from F6 to F7 generation. The results showed that:The paramer of variability width and broad-sense heriTableility were obvious among hybrid progenies. The heriTableility of amylose content in hybrid progenies was about 99.89%~100%, and increased with the advance of generation. Correlation analysis showed that amylose content among different generations were significantly related and correlation values of neighbor generations were higher.When amylose content was as a selection standard, by use of selection for high or low amylose content in progenies, the amylose content of progenies could significantly increase or decline. In addition, selection effect of low amylose content was better than that of high amylose. In the early generations, the selection should not be too strict, but 10% was suiTablele in F6 and F7.Cooking and eating quality properties and yield traits were affected to some extent by amylose content selection, and the degree varied with crosses and traits. Breakdown and Setback were affected more among cooking and eating properties while granule number per spike and grain weight per plant were affected more among agronomic traits.Correlation analysis showed that correlation degree and nature between cooking and eating quality properties varied with amylose content increasing or declining. The relationship between amylose content and cooking and eating properties was not simply linear, so that amylose content which was too high or too low would lead to cooking and eating quality degrade to what extent. It was found that progeny populations with intermediate amylose content possessed better cooking and eating quality.Amylose and protein, which were important factors affecting cooking and eating quality,were main compenents in rice grain. There was negative correlation relationship between amylose and protein content. Therefore, coordinating protein content with amylose content was an important approach for improving rice quality.Relationship between amylose content and Key Amylosynthetase varied with amylose content change.With amylose content increase ,ADPG glucose pyrophosphorylase and soluble starch synthase increase.Inversely,starch branching enzyme decline .Genetic similarity analysis based on SSR molecular marker showed that average genetic similar index of single hybrid progency ranged 0.473 to 0.750 and its mean was 0.581, while that of paired hybrid progency was 0.992 to 0.054 in cross I. Sililarly, single hybrid progency ranged 0.485 to 0.714 and mean was 0.579 while that of paired hybrid progency was 0.992 to 0.031 in cross II.Cluster analysis of parents and progencies indicated that hybrid progencies with high amylose content and the parent with high amylose content clustered together, hybrid progencies with high amylose content and parent with high amylose content clustered together. Successive direct selection for some trait of hybrid progenies, genetic background of their progenies deviated to one of the parents. Genetic relationship between selected progenies were close to one of parents, which wasn't beneficial to paramiding of excellent gene from parents and genetic diversity of progenies.