Studied On Genetic Variability If Amylose Contein In Rice Grain And Its Selection Efficiency In The Early Generations Of Rice Crosses

Cooking or eating quality of rice quality was an important quality trait, and amylose content wasone of the main factors which affected the cooking and eating quality, early hybrid generation wasimportant generation that traits separated and was selected. Therefore for breeding high yieldcultivars with super quality it was important in theory and practice to study the genetic variability ofamylose content in rice grain and its selection efficiency in the early generation of rice crosses. In thisexperiment two crosses-Xixuan 1×Tong 769, Dongnong 423×Fukei 180-were made using fourJaponica rice parents with difference in amylose, and genetic variability and selection efficiency ofamylose content were studied in hybrid progenies from F2 to F5 generation. The results showed that:The pammer of variability width and broad-sense heritability have obvious between hybridprogency. F₂ generation of crossâ… presented approximately deviating from normal distribution incontinuous variation and crossâ…¡presented deviating from normal distribution in continuousvariation. F₂ generation of two crosses tended to low amylose content and emerge ultra-parentsvariation. There were no main gene different among two parents. Amylose content in rice grain,which belonged to quantitative trait, was mainly controlled by polygenes with small effects, and geneadditive effect was most important for amylose content in the early generation while dominant effectalso play some roles. The heritability of amylose content in hybrid progenies was about64.48％～95.34ï¼…, and increased with the advance of generation. Correlation analysis showed thatamylose content in different generations had significant correlation and correlation values ofneighbor generations were higher.When amylose content was as a selection index, selecting for high or low amylose content inprogenies, the amylose content of progenies could significantly increase or decline. It was found thatselection effect for selecting low amylose content was better than for high amylose. In the earlygenerations the selection should not be too strict, and 15ï¼…selection intensity was suitable in F₂generation, but 10ï¼…was suitable in F₃,F₄ and F₅.Cooking and eating quality properties and yield traits were affected in different degree byselecting amylose content, and the degree varied with crosses and traits. Setback and breakdownwere affected more among cooking and eating properties while heading stage were affected moreamong agronomic traits.Correlation analysis showed that correlation degree and nature between cooking and eatingquality properties varied with amylose content increasing or declining. The relationship betweenamylose content and cooking and eating properties was no simply linear, so that amylose contentwhich was too high or too low would lead to cooking and eating quality degraded at different degree.It was found that progeny populations with middling amylose content possessed better cooking andeating quality.Amylose and protein, which were important factors affecting cooking and eating quality, weremain compenents in rice grain. There was negative correlation relationship between amylose andprotein content. Therefore coordinating protein content with amylose content was an important approach for improving rice quality.Genetic similarity analysis based SSR molecular marker showed that single hybrid progencyranged 0.468 to 0.624 and mean was 0.556 while that of paired hybrid progency was 0.929 to 0.143in crossâ… . Genetic similarity analysis based SSR molecular marker showed that single hybridprogency ranged 0.500 to 0.595 and mean was 0.560 while that of paired hybrid progency was 0.938to 0.125 in crossâ…¡. Hybrid progency of two crosses were higher similar female parent than maleparent.Cluster analysis of parents and progencies indicated that high amylase hybrid progencies andhigh parent could cluster together, low amylase hybrid progencies and low parent could clustertogether. Successive selecting for trait of hybrid progenies, genetic background of its progeniesdeviate to one of parents. Genetic relationship of selected progenies closed to one of parents, whichwasn't beneficial to excellent gene of, polymeric parents and genetic diversity of progenies.