暗玉米(opaque-2)蛋白質含量之遺傳

Abstract

The inheritance of grain protein in ordinary corn has been reported by many workers, but not in opaque-2 corn. The purpose of this study is to investigate the gene effects for grain protein of opaque-2 corn in order to provide information for breeding high protein opaque-2 corn. The high protein parent with protein content 17% was a selfing line of Illinios High Protein o2 corn (IHPo2) and three low protein o2 parents, TA 604, TA 606 and TA 614 were inbreds developed by the Taiwan Agricultural Research Institute with protein content ranging from 12.6% to 14.7%. Three crosses, IHPo2 × TA 604, IHPo2 x TA 606, and IHPo2 × TA 614 and their reciprocals were made. The grains of F1, F2 and BCs, populations for protein analysis were obtained in the same crop season in order to avoid the climatic effect on grain protein. Only the reciprocal cross, TA 604 × IHPo2 was used to obtain F2,BC1 and BC2 populations. The different populations from each cross were grown in the field using randomized complete block with two replications. The numbers of plant grown for various populations were P1 and P2, 100 each; F1, 50; F2, 500; BC1 and BC2, 250 each. The protein was analyzed by using Udy rapid Protein analyzer. The total number of samples analyzed in this study was 1, 329 (shown in Table 1) . Both Gamble (1961) and Hayman (1958 ) formula were used in analyzing protein data. The results from both Gamble and Hayman formula showed quite in agreement (Ta-ble 2). Cross II fitted the additive-dominance model while crosses I and III did not. Based on Gamble's six-parameter model, it showed that there was highly significant additive effect for all crosses. There were also significant dominance effects for crosses I and III, but not for cross II. The positive dominance effects indicated that high protein was partially dominant. This result was contradictory to the previous report on ordinary corn (5, 6, 8, 9, 12, 13, & 14). We assume that this might be resulted from the effect of opaque-2 gene because the opaque-2 corn always has larger embryo and higher protein content (Nelson, 1969; Wan, unpublished data). The low protein parents used in this study also showed higher protein content as compared with their normal version inbreds. It was also shown that there were significant additive × additive (The symbol is abbreviated), additive × dominance (The symbol is abbreviated) and dominance × dominance (The symbol is abbreviated) effects in crosses I and III, but not in cross II indicating that the gene effects in cross H (parent TA 606) were different from that in crosses I and III (parents, TA 604 and TA 614) . In crosses I and III, the dominance effects ((The symbol is abbreviated)) were positive and dominance × dominance effects (The symbol is abbreviated) were negetive indicating that the interaction effects were resulted from the action of duplicate genes. No cytoplas-mic effect was found in any of the three crosses studied. Since there are highly significant additive effects in all crosses, it is suggested that selection for high protein in o2 corn is effective. However, rigid selection should be prac-ticed if breeders are working on this character because significant dominance and interaction effects were also present in two of the three crosses.