Studies On Genetic Variability Of Protein Content In Rice Grain And Its Selection Efficiency In The Early Generations Of Rice Crosses

Cooking or eating quality was an important quality trait, and protein content was one of the main factors which affected the cooking and eating quality. Therefore for breeding high yield cultivars with super quality it was important in theory and practice to study the genetic variability of protein content in rice grain and its selection efficiency in the early generation of rice crosses. In this experiment two crosses–Xixuan 1×Tong 769, Dongnong 423×Fukei 180–were made using four Japonica rice parents with difference in quality and yield, and genetic variability and selection efficiency of protein content were studied in hybrid progenies from F2 to F4 generation. The results showed that:Protein content in rice grain, which belonged to quantitative trait, was mainly controlled by polygenes with small effects, and gene additive effect was most important for protein content in the early generation while dominant effect also play some roles. F2 generation presented approximately deviating from normal distribution in continuous variation and tended to high protein content. The heritability of protein content in hybrid progenies was about 61.2%~96.7%, and increased with the advance of generation. Correlation analysis showed that protein content in different generations had significant correlation and correlation values of neighbor generations were higher. Though the parents in this experiment had no significant difference in protein content, there were many ultra-prents variations in hybrid proenies, and selecting for high or low protein content from F2 generation, respectively, progenies which were over the high-parent or negative for the low-parent could be obtained.When protein content was as a selection index, selecting for high or low protein content in progenies, the protein content of progenies could significantly increase or decline. It was found that selection effect for selecting high protein content was better than for low protein. In the early generations the selection should not be too strict, and 15% selection intensity was suitable in F2 generation, but 10% was suitable in F3 and F4. Cooking and eating quality properties and yield traits were affected in different degree by selecting protein content, and the degree varied with crosses and traits. Setback and breakdown were affected more among cooking and eating properties while heading stage and yield were affected more among agronomic traits.Correlation analysis showed that correlation degree and nature between cooking and eating quality properties varied with protein content increasing or declining. The relationship between protein content and cooking and eating properties was no simply linear, so that protein content which was too high or too low would lead to cooking and eating quality degraded at different degree. It was found that the higher protein content was, the lower rice yield was, and that progeny populations with middling protein content possessed better cooking and eating quality, at which the contradiction between high yield and super quality could be coordinated, but if the nutritive quality or yield was emphasized, it was difficult to coordinate high yied with super quality.Protein and amylose, which were important factors affecting cooking and eating quality,were main compenents in rice grain. There was negative correlation relationship between protein and amylose content. It was protein content that affected the cooking and eating quality of progenies with...