Studies On Mechanism Of Good Quality And High Yield Of Liaojing Rice Varieties

Trough pedigree analysis, the parental relationship of rice varieties planted in Liaoning and the breeding principles of Liaojing rice varieties were studied. The filling characteristics of grains at different grain position and its relationship with rice quality were studied using 30 varieties with different panicle type planted in Liaoning. Based on crosses from five sterile lines and five restorers in japonica rice, the inheritance effects of filling rate of superior and inferior grains in F₂, F₃ and parents at different developmental stage of rice were studied by using condition inherit variance component analysis method. The polymorphisms were tested in ten Liaojing rice varieties by using 41 pairs of SSR primers. The results are as follows:1 The breeding route for Liaojing rice varieties was aimed at high yield, fine quality, multiple resistance and wide adaptation as target, directed with the combination between ideal plant type and advanced heterosis as well as optimized components, and adhered to 'enriching genetic backgrounds, broadening mutation, enhancing kernel setting of offspring and promoting offspring selection effect'. The practical characters for developing Liaojing rice varieties were taking ideal nplant type materials from indica and japonica rice as bridge, and local varieties planted in large area as elite parents, applying multi-composite crossing techniques, combining multi-location ecological selection, united resistance assessment, and shuttle breeding at different locations between the south and north to breed new japonica rice varieties. Liaojing 454, Liaojing 294 and Liaojing 9 are characterized with high yield and fine quality because of more primary rachis branches, longer leaf life, stronger photosynthesis and higher percentage of ripened grains.2 Based on filling status, the middle grains contributed greater to the yield. The filling rate of mid-top grains of erect panicle type varieties was larger, but the filling rate of bottom grain was lower, than that of curved panicle type varieties. Bad filling of bottom grains of erect panicle type varieties led to the low filling rate of whole panicle. There was a close correlation between yield traits and grain filling rate, because suitable panicles could increase panicle length, number of primary rachis-branches and filling rare resulted in good plumpness. Grain plumpness had significant correlation with brown rice rate. The general performance of brown rice rate at the grain position was top>middle>bottom and primary rachis branches>secondary rachis branches. The brown rice rate of bottom grain was lower in erect panicle type varieties. Increasing the filling rate was helpful to improve the milling quality of curved panicle type varieties, but had dual effects in erect panicle type varieties in that with the increase of brown rice rate, the grain tended to be brittle, thus lowering the head rice rate. The grain plumpness had very significant negative correlation with the ratio of length to width. The orders of amylose content in grain position were top primary rachis>middle primary rachis>bottom primary rachis>top secondary rachis > middle secondary rachis>bottom secondary rachis. Erect panicle type varieties were characterized with high amylose content, low alkali spreading value, low comprehensive evaluation values in terms of appearance,stickiness and palatability. Varieties with high whole brown rice rate had good palatability.3 The main inheritance effect controlled by maternal and nuclear genes inheritance systems dominated at early-medium filling stages for superior grain and additive effect dominated at the medium stage. The main effect variance was equivalent to interaction variance of environment by genotype for inferior grains. The inheritance effect was controlled by endosperm genotype and additive variance dominated at the medium stage. The phenotype variance of all quality traits was controlled by genotype variance. Milling quality, thickness, grain type and protein content were mainly controlled by maternal body and seed; amylose content was affected by endosperm, maternal body and cytoplasm; Gelatinization temperature was controlled by cytoplasm and endosperm genotype. Japonica hybrid rice had heterosis in quality, especially in chalkiness. The ascending direction of positive heterosis was milling quality, grain weight and gelatinization. Amylose content and ratio of length to width showed negative heterosis. The milling quality decreased and amylose content increased as grain position descended. Superior grains were rather long and had small chalkiness size.4. The polymorphisms were tested in ten Liaojing rice varieties by using 41 pairs of SSR primers. The polymorphisms were showed in 22 pairs of primers, of which 12 pairs showing stable and clear bands were considered as fingerprints. The fingerprint maps were drawn.