Evaluation of Heterosis in Cultivated Barley Varieties

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It has been known that there are several barriers to hybridization between barley varieties: hybrid brittleness, hybrid weakness and hybrid lethal etc. In this study, therefore, experiments on heterosis in barley was made within the limit of rather narrow crossing. Seven kinds of experiments are carried out in this study. (1) Studies on combining ability between six-rowed barley varieties originated in East Asia, (2) heterosis in two-rowed barley varieties, (3) evaluation of combining ability by means of diallel crosses in barley, (4) expression of heterosis in stem length of F_1-hybrids between wild barley, Hordeum spontaneum, (5) heterosis in stem length of F_1-hybrids in cultivated two-rowed barley, (6) relation between heterosis in mature and juvenile plants and (7) comparative investigation of heterosis effect under two different planting densities. In the Experiments(1), (2), (4) and (5), top cross system was used in which one or two varieties were taken as the donor parents, res … More pectively.In present study, high heterosis for yielding performance was obtained in F_1-hybrids within comparatively narrow range of crossing such as six-row type, two-row type and also uzu or semi-brachytic type, respectively. However, there were some tendencies to become larger expression of heterosis in F_1-hybrid between varieties collected from further distant. F_1-hybrid plants generally tended to elongate in stem length too much. So, dominant gene or genes for short stem were searched in this study, but no one dominant gene for short stem was found so far as 150 or more crosses were tested. Diallel analysis using 10 varieties showed significantly additive and dominant effects in yield and most of yield component characters, and some of cross combinations represented general or specific combining ability. Furthermore, results of growth analysis, made by F_1-hybrid plants and varieties, showed that major indications of growth or total dry weight, relative growth rate, net assimilation rate and leaf area ratio, have had non-significant relation with final grain yield of the plants. Less