Abstract
Following the previous papers (SYAKUDO, K.and KAWABATA, S. 1961 and 1962a), it is the chief purpose of this paper to report the underlyinginformation on the utilization of hybrid vigor in Renge breeding. Results obtained are summarized as follows 1) A considerable variation is found in forage yields of 28 F1 hybrids of all possible combinations among 8 inbred lines, ranging from 289. 2g to 488.5g in average yields per plant and from 163.8g to 368.9g in F1 ?? P (MP : Mid-parent). As previously noted, this fact suggests that it is important to select inbred lines showing high combining ability. Decline of fcrage yields due to inbreeding is, on the average, recovered in the F1 plants among inbred lines. Accordingly, the F1 hybrid having significantly higher yields than the mean yield of F1 Iines tested seems to produce superior yields to an original open-pollinated variety. 2) A positive high correlation is found in forage yields between open-pollinated and diallel crossed progenies. It indicates that general combining, ability may be evaluated by open-pollinated D. roge-lries, too. 3) Genic male sterility and incompatibility do not occur in Renge. Therefore, the breeder can not produce hybrid seeds by utilizing therse phenomena. As this legume is highl cross-pollinated, the breeder can, however, easily produce hybrid seeds by means of a mixed planting of some inbred lines, permitting mixing of some selfed or sibbed seeds into hybrid seeds. By this method the authors, obtained hybrid seeds and then compared the performance of these hybrid seeds with that of the leading commercial variety, Gifu-Daibansei. As a result of this test, significantly b.igher yielding hybrids than Gifu-Daibansei were found with rela-tively high frequency. 4) According to this method for producing hybrid seeds, a certain percentage of self.ed or sibbed seed from the parent plants is carried into the hybrid seed. Consequently, the competition between hybrid and parent plants comes into question as a factor in determining the yields. To study this problem, mixtures of parent and hybrid Renge seeds, together with pure seeds of the parents and hybrids, were planted at three different seeding rates. The forage production of the 80% hybrid mixture planted in the congested condition, does not differ significantly from that of the pure hybrid. These results suggest that any seed mixtures may be expected to yield about as much as pure hybrid seeds do. 5) From these findings, it is concluded that the utilization of hybrid vigor is very promising for Renge breeding.
