Inheritance Of Grain Weight And Its Correlation With Appearance Quality In Japonica Rice (Oryza Sativa L.)

6 parents with major difference in gram weight and appearance quality were crossed in complete diallel design to study the genetic characters of grain weight and their correlation with appearance quality by way of analyzing grain traits of 30 F1 hybrids,14 F2 offsprings ,8 BC1F1 populations and 1 F3 line in japonica rice. The results were summarized as follows:(1) Grain weight of upper panicle has less variance and large grain than others, the effect of panicle position on variation of large grain variety was the biggest, selecting upper panicle is the most suitable.(2) No significant cytoplasmic effect on grain weight ,grain length, grain width, grain thickness and milling and appearance quality were tested.(3) There were no obvious heterosis in grain traits, but difference in combinations; When grain weight was lighter, the partly positive heterosis in F1 was manifested; with the increase of grain weight of parent, the heterosis decreased and gradually became partially negative heterosis. The positive correlations between expressional value of FI and parents value and the negative correlations between heterosis index of F1 and parents value were tested .(4) Grain characters has high heritabilities, the inheritance of grain weight and grain thickness were affected by additive gene effects.But additive and dominant gene effects had the same importance to grain length and grain width, all traits were affectedby some epistasis gene effects.(5) As a quantitative-quantitative trait, grain weight was controlled by 1 major gene and many minor genes, the higher grain weight was, the more minor genes. Dominant effect and recessive effect of major gene and minor genes were partially.(6) The significant positive correlations between grain weight and chalkiness was tested, the effect of grain width on appearance quality was the biggest; it was hard to select good appearance quality combination if grain weight exceed 32g; length/width ratio vary from 2.0 to 2.3 was suitable, if grain weight was larger ,the ratio may rise to 2.5; back-crossing with good quality parent was beneficial to improve the selective efficiency of offspring.