我が国では、戦前から戦後にかけてオオムギ栽培が盛んに行われたが六条オオムギが主であった。しかし、昭和30年代になると醸造用あるいは飼料用として二条オオムギの栽培が盛んになり、最近では従来の六条オオムギから二条オオムギにほとんど置き替わっている。我が国における二条オオムギは明治以後欧州あるいは米国から導入された品種が、選抜を受けたり交配母本に用いられて定着したもので、我が国在来の六条オオムギにくらべて歴史は新しく（高橋ら1981）。これらの二条品種は日本の風土に適するように改良が加えられていることはもちろんであるが、それにしても、二条性そのものが我が国にはなかった形質であり、春播性、ウドンコ病抵抗性、短毛底刺などいわゆる外来の特徴を併せ持っている。このような外来の形質そのものがどの程度我が国の環境条件の中で生かされ、いわゆる日本化が進んでいるかは、今後の二条オオムギ育種上極めて有用な知見になるものと思われる。そのためには日本で栽培されている二条品種と、外国の二条オオムギの主な分布地域から収集した品種とを比較対照して、生理、遺伝的解析を進める必要がある。本研究はこのような意図の下に行われた。以下に結果の概要を示す。

The two-rowed barley cvs that have been cultivated in Japan are used exclusively for brewing purposes. These cvs consist of the selections made from hybrids betweena small number of two-rowed cvs first introduced from Europe and North America in the early Meiji era about 100 years ago. This study aimed to find how these current cvs have changed in the characters of ecological and agronomical importance from the two-rowed cvs introduced into Japan from different geographical regions. A total of 150 two-rowed cvs consisting of 55 Japanese cvs, 34 Turkish cvs, 47 European cvs and 14 Ethiopian cvs were randomly taken from the stocks preserved in the Barley Germplasm Center of Okayama University. The results are summarized as follows; (1) When sown outdoors in fall at Kurashiki, Japanese cvs showed large varietal variation including a wide spectrum of heading times ranging from very early to late. Turkish and European cvs mainly consisted of mid-season and late types whereas Ethiopian cvs were all of mid-season type. Regression coefficient (byx) of heading time in the field (y) on time of spikelet differentiation stage (x) was 0.57 for Japanese cvs, and this value was intermediate between the Turkish (0.37) and the Ethiopian (0.77) cvs. The byx of European cvs (0.45) was similar to that of Turkish cvs. (2) Time of flag-leaf emergence under 20h-day at medium to high temperature (earliness in a narrow sense) was investigated at both 25℃ and 15℃ after full vernalyzation of germinated seeds. Turkish cvs were early in flag-leaf emergence under both conditions, but European cvs were later on average. japanese and Ethiopian cvs showed large variation between cvs. (3) Time of flag-leaf emergence under 12h-day (photoperiodic response) was also investigated at both 25℃ and 15℃ after vernalization . European cvs showed late emergence of flag-leaf under these conditions, and the retardation of flag-leaf emergence was larger at the lower temperature. Japanese cvs showed large variation in time of flag-leaf emergence at both temperatures. When the sensitivity to short photoperiod was calculated it showed a similar pattern to the above. (4) With respect to agronomic characters other than ear emergence, Japanese cvs had, in general, shorter spikes and spike internodes, less spikes per plant but high rates of spike exsertion compared to the cvs from foreign countries. However, the Ethiopian cvs showed a higher grade of spike exsertion. (5) Finally principal, component analysis was applied to all of the characters measured. The first, second and third principal components accounted for sixty two percent of the total variation. The first component appears to represent the earlier heading, and the second component appears to be plant growth characteristics. The third one includes the factors related to grain filling. All of the cvs tested were scatterd on the plant defined by the first and second principal components as shown in Fig. 1. From the ecological view point it may be concluded that Japanese two-rowed barley cvs differ markedly from European two-rowed barleys, whereas both Turkish and Ethiopian two-rowed barleys are rather intermediate between Japanese and European ones.