(35(4):401-412)Genetic Studies on Larger Kernel Size of Rice－II. Inheritance of Grain Dimensions of Brown Rice

以包括親本與正反交組合之9 × 9 全互交F1材料探討大粒水稻穀粒性狀之遺傳。數據經以Griffing 及Jinks-Hayman 等兩套不同方法分析，結果發現糙米粒長、粒寬、長寬比及千粒重等4 穀粒性狀親本間之遺傳變異均極大，此變異係由累加性與顯性效應所引起，被評估之4 個穀粒性狀之累加性效應均遠大於顯性效應。4 個穀粒性狀之一般與特殊組合力均極顯著，且一般組合力效應又遠大於特殊組合力。4 個穀粒性狀之狹義遺傳率均頗高，亦發現均存在有細胞質效應。經由回歸與變方分析估得4 個性狀之顯性程度均屬部份或不完全顯性。正負等位基因之頻度在親本間之分布除粒長為相等外，餘3 性狀均不等。粒長及粒寬之顯性基因數約等於隱性基因數，而長寬比及千粒重等兩性狀之顯性基因數則多於隱性基因數。經藉迥歸圖析及親本顯性次序之判定，粒長、長寬比及千粒重為單方向顯性，粒寬則為雙方向顯性。 The inheritance of grain dimensions of brown rice of larger kernel size of rice were studied by means of a 9 x 9 diallel crosses including parents and reciprocal crosses. Data from the F1 generation and parents were analyzed using the Griffing and the Jinks-Hayman methods of diallel analyses. The genetic variations of four grain traits, grain length, grain width, length/width and 1000-grain weight, were significant among the parents. Both additive and dominance effects were important for all four graifn traits. Furthermore additive effects were significantly larger than dominance effects for these grain traits studied. Highly significant general combining ability (GCA) and specific combining ability (SCA) effects were observed for these grain traits. The GCA effects were much more important than SCA effects. Estimated narrow-sense heritia-bilities for all these grain traits were very high indicating that a major portion of pheno-typic variabulity was controlled by additive effects. Maternal effects existed in all four grain traits. Degrees of dominance of four grain traits estimated by graphic and variance analyses showed partial or incomplete dominance. The average frequency of positive and negetive allel in parents were about equal for length/width, but not equal for the others. Number of dominant genes exceeded recessive genes for length/width and 1000/grain weight, however, both dominant genes and recessive genes were equal for grain length and grain width. Dircetions of dominance evaluated by regression plotting and the order of parental dominance were unidirection for grain length, length/width and 1000-grain weight and ambidirection for grain width