抄録
Parental characteristics in the hybrid progeny of the two rice species were observed in B2F1 plants and B2F6 (including a few B1F6) lines obtained from backcrosses between a sativa and a glaberrima strain. The backcross derivatives had different coefficients of relationship to glaberrima (or to sativa) parent ranging from 1/8 to 7/8. Ligule length, regenerating ability of excised stem segments, and various other characters were recorded. The measurement of a plant, i, for a character was evaluated by xi=(Xi-μ)/d, where μ=1/2(Xs+Xg), the mid-parent value, d=1/2(Xs-Xg), and Xs and Xg are the parental sativa and glaberrima values, respectively.
The distribution of x values showed appreciable transgressiveness (overlap) in panicle axis diameter and three other characters, particularly in the B2F6 population, presumably as a result of gene recombination. Awn length also served as a measure of gene recombination since both parents were awnless. The standard deviation of x values for different characters was used as an index showing recombination of parental characteristics or “character discordance”. These data suggested that parental genes could be recombined almost freely. In ligule length and some other characters, however, B2F6 lines showing parental values (xs=1; xg=-1) were larger in number than those showing intermediate values, and the lines showing intermediate values tended to have a low productivity. Awn length was inversely correlated with seed productivity. Further, between two independent gene loci, a tendency toward restricted recombination was detected. These facts were considered as indications of so-called M-V linkage. Among the characters investigated, the probability of misclassification between the two species, estimated from intra- and inter-specific variations, was correlated with transgressiveness in the hybrid. Ligule length and secondary branch number per primary branch, which seemed to be useful as key characters, were practically non-transgressive and were subjected to M-V linkage more obviously than other characters.
