オオムギの葉の剛毛に関する遺伝子分析

The inheritance and linkage relationship of a new hairiness trait "large trichome" was investigated in barley. Although the size of large trichome is about four times that of normal one, the character can not be recognized with the naked eye. However, it is easily identified by the roughness of leaf touch. The large trichomes develop on both sides of the leaf blades. The direction of trichome is both acropetal and basipetal. It is clearly distinguished from the extremely long trichome controlled by Pub gene. About 2,300 varieties of our Barley Germplasm Center were screened by the leaf touch to find nine varieties with large trichome. Two of them were six-rowed local variety from Pakistan, and other seven were two-rowed varieties from Europe and Japan. All of them were hulled type. Crosses of six large trichome varieties with a normal Japanese variety resulted in the large trichome type F1s, suggesting the dominant nature of the trait. The large trichome line Hokuiku 17 was crossed with various linkage testres to study the mode of inheritance and the linkage relationship of the gene. In the F2 populations, the large trichome was controlled by a single dominant gene named Ltr (large trichome), which was independentiy inherited from the following marker genes; br and gl-5 on chromosome 1; li and ν on chromosome 2; uz on chromosome 3; K and gl-3 on chromosome 4; trd on chromosome 5; ο on chromosome 6. On the other hand, from the cross between Hokuiku 17 and OUL166, Ltr was found to be linked with s and fs on chromosome 7. Although the allelism test has not been completed, the very low frequency of the large trichome type (9/2,300) indicates that the variant resulted from a recent mutation event, or the fitness of the variant is low in the natural and/or artificial selection.

岡山大学資源生物科学研究所大麦系統保存施設が保有するオオムギのうち約2,300品種を対象として、葉身の表面に生じる毛（trichome）の変異体を検索した。1）2,300品種のうち9品種（0.4％）が葉身の表面に剛毛を生じた。2）通常の品種では毛茸の鈎状部分の長さが約10μmであるのに対して剛毛型の品種では約40μmであった。Pub遺伝子による長毛はこれよりはるかに長く、剛毛型とは明らかに異なった。3）剛毛型は優性の1遺伝子（Ltr,large trichome）に支配されており、連鎖分析の結果、第7染色体にLtr-s-fsの順に配列されることが明らかになった。