オオムギの雑種強勢に関する研究

In cultivated barley, various hybrid injuries such as brittle rachis and hybrid weakness occur. Therefore, crossing must be done among cultivars to prevent the occurrence of such hybrid injuries. In the present study, we examined the magnitude of the heterosis in the crossings and geographical distribution of barley cultivars concerning heterosis. A few Japanese cultivars were used as the common parent for crossing. (1) In the six-rowed barley, 43 cultivars collected from Japan, China and Korea were crossed with non-uzu covered and naked cultivars, Shiroyo-shigara 2 and Nami-Akashinriki, respectively. The largest magnitude of heterosis in grain yield per plant was obtained in the crossing between the Korean cultivar and one of the Japanese common parents. (2) Heterosis in two-rowed cultivars was investigated using a total of 156 F1S which were cross combinations of cultivars collected from the world with two common male parents, Amagi Nijo and Kawasaigoku. The heterosis was larger larger in the cross combinations with Turkish and Ethiopian cultivars. The largest F1/BP was 1.66 in Turkish and 1.45 in Ethiopian cultivars. (3)　As to uzu or semi-dwarf cultivars peculiar to Japan, 34 cultivars were crossed with two common male parents, Sekitori (covered) and Akashinriki (naked). Expression of the heterosis was rather conspicuous in the crosses of covered×naked cultivars than those of covered×covered and naked×naked ones. (4) Half diallel analysis using 10 two-rowed cultivars showed that one Ethiopian cultivar expressed a high grade of general combining ability and that one French cultivar was of higher specific combining ability. (5) The most effective agronomic character of the two-rowed cultivars to the grain yield per piant was number of ears in an ordinary year, while in the wet year it was 1000 grain weight. This was considered to be due to overluxuriant growth accompanied by lowering of the percentage of ripened grain. However, in some cultivars the percentage of ripened grain was not lowered under the overluxuriant growth condition.