Studies on chinese cabbage breeding. (II)

Abstract

The purpose of this study was to find the most promising F1 hybrids by crossing several self-incompatible strains of induced pseudogamy in Matsushima No. 2 and Chiba No. 1 chinese cabbage. The authors obtained 48 F1 hybrids by crossing 23 self-incompatible strains. The seeds of these F1 hybrids were sown on the two different dates. The hybrid vigor and the various characteristics which appeared in these F1 hybrids, were observed. (1) In crossing these self-incompatible strains, hybrid vigor was affected by different cross-combi-nations and different sowing dates, and especially the total weight, head weight etc. were increas-ed by hybridization. (2) The rate of increase in F1 hybrid yield was greater than that of their parents, in both early and late sowing, and the variation in their yield was greater than those of other characteristics. It is thus possible to find a fairly productive F1 hybrid. (3) Generally, the degree of hybrid vigor which appeared in early maturity and leaf number was less in comparison with those of other charac-teristics. However, a few of these cross-combi-nation showed marked vigor in early maturity and leaf number characteristics. Therefore, it was possible to select the hybrids that matured earlier, and had more leaves per head than Matsushima No. 2. (4) There was correlation between a superior parent yield, an average yield of parents and F1 hybrid yield, respectively, but no correlation be-tween an inferior parent yield and F1 hybrid yield. The F1 hybrid resulting from crossing productive parents showed increased vigor, when their parents were homozygous. (5) In general, F1 hybrids resulting from the crossing of these self-incompatible strains did not have more excellent characteristics than those of standared variety, Matsushima No. 2. However, some of these F1 hybrids seemed markedly promising. Finally, we selected 6 F1 hybrids that had showed adaptability to early sowing and late sowing, which were superior in early maturity, yield, uniformity and disease-resistance (soft rot) to Matsushima No. 2.