水稻數量性狀遺傳之研究 II.秈稉稻品種間之完全組合互交

Abstract

Two indica varieties (P1=Chianung sen No. 11, P2=Taichung Native No. 1) and two japonica varieties (P3=Tainan No. 5, P4=Tainung 67) were used as materials in this experiment. Crosses were made between these varieties in accordance with a diallel scheme, including reciprocals and selfing. The purpose was to study the genetic behavior of several important quantitative characters. The results were summarized as follows: 1. The four parents differed significantly in the agronomic characters of plant height, panicle length, seed fertility rate and 1000-grain weight. Dominance effect in these characters was observed in the F1 progenies. Significant differences were also observed among diallel crosses. 2. Dominant variance (H1) for various characters was greater than additive genetic variance (D). The values of (H1/D)(superscript 1/2), an expression of degree of dominance, was larger than 1 for many characters investigated except fertility rate and number of spikelet per panicle, suggesting total dominance or over-dominance. For plant height, panicle number, spikelet number and fertility rate, H1≠H2, 1. e., u≠v, was recorded, indicating the dominance for these characters was partially contributed by the unequal frequencies of dominant and recessive genes. As K(subscript D)/K(subscript R) equals to 1 for panicle lenth and 1000-grain-weight, an equal number of dominant and recessive genes was therefore possible. Results of h^2/H2 indicated that the degree of dominance was controlled by 1-2 pairs of dominant genes for all the characters studied. 3. Seed fertility rate of F1 progenies from crosses between indica and japonica varieties ranged from 58-82% and could be further increased if selections were made in later generations. The other three yield components, panicle number, number of spikelet per panicle and 1000-grain-weight, of F1's had also been found to be superior to parents in many cases. It is therefore possible to breed new rice varieties through the crosses between indica and japouica varieties in the future.