オオムギの近辺野生種と栽培種における未熟胚由来カルスからの再分化能の比較

The variation in shoot regeneration obility of calli derived from immature embryos was examined in 95 wild strains, 82 of which were of Hordeum spontaneum and 13 of which were H. agriocrithon, and 87 cultivated varieties collected from various countries or regions of the world. In 85 strains of the wild species, a number of calli regenerated shoots, and their proportion ranged from 1.2% to 75.7%. The average percentage of shoot regenerating calli was 21.7% among the strains that formed calli, 11.5% of which regenerated green and 10.2% albino shoots. On average, 21.4% and 23.9% calli regenerated shoots in H. spontaneum and H. agriocrithon, respectively and there was no significant difference between these values. A significant difference in the percentage of shoot regenerating calli was found among six variants (dawense, ishnatherum, laguncliforme, paradoxon, proskowetzii, spontaneum) which were comprised in H. spontaneum. In 73 varieties of cultivated species, there were shoots regenerating calli likely to wild species, and their proportion ranged from 3.2% to 85.5%. The average percentage of shoot regenerating calli was 25.4%, 22.0% of which regenerated green and 3.4% of which regenerated albino shoots. There was a significant difference in percentage of green shoots regenerating calli against shoots regenerating ones between the wild (53.0%) and cultivated species 886.6%). The two kinds of non-brittle rachis genotypes, Bt bt2 and bt Bt2 are one of the key characters distinguishing the oriental and occidental types of cultivated barley. The average percentages of shoot regenerating calli were 16.2% and 32.3% for the genotypes Bt bt2 and bt Bt2, respectively, suggesting that there is a geographical variation in the shoot regeneration ability of calli in the cultivated species. By contrast, the oriental and occidental strains of wild species showed no difference in the shoot regeneration ability of calli. The geographical variation of shoot regeneration ability differed significantly between wild and cultivated species. This suggests that the geographical variation of shoot regeneration ability occurred after the cultivation of the barley was established.

本研究ではオオムギ近緑野生種Hordeum spontaneum82系統とH.agriocrithon13系統、計2種95系統および世界各地の栽培種87品種を供試して、未熟胚由来カルスからの不定芽再分化能を調査し、近緑野生種と栽培種における再分化能の品種変更およびその地理的分化を比較した。近緑野生種では95系統中94系統がカルスを形成し、そのうち85系統（90.4％）が不定芽を再分化して、不定芽再分化率は系統によって1.2％から75.7％まで幅広く変異した。カルスを形成した94系統における不定芽再分化率の平均値は21.7％、緑色不定芽再分化率は11.5％、アルビノ不定芽再分化率は10.2％であった。H.spontaneumとH.agriocrithonの不定芽再分化率の平均値はそれぞれ21.4％と23.9％で、有意差は認められなかった。しかし、H.spontaneumに含まれる6品種（dawense, ishnatherum, laguncliforme, paradoxon, proskowetzii, spontaneum）の間では不定芽再分化率に差異が認められた。栽培種では供試品種のすべてがカルスを形成し、そのうち73品種（83.7％）が不定芽を再分化して、不定芽再分化率は品種によって3.2％から85.5％まで幅広く変異した。供試品種全体の不定芽再分化率の平均値は25.4％、緑色不定芽再分化率は22.0％、アルビノ不定芽再分化率は3.4％であった。このように、不定芽再分化率に対する緑色不定芽再分化率の占める割合は栽培種で86.6％、近緑野生種で53.0％となり、両者に大きな差が認められた。供試した栽培種を小穂非脱落性に関する遺伝子型によって東亜地域に多く分布するBt bt2型と西域に多く分布するbt Bt2型に分けて不定芽再分化率を比較すると、Bt bt2型の平均値は16.2％、bt Bt2型の平均値は32.3％となり、bt Bt2型の不定芽再分化率が有意に高く、地理的分化が認められた。しかし、近緑野生種では不定芽再分化能の地域間差がみられないので、オオムギの祖先種が栽培化されてから不定芽再分化能の地理的分化が生じたものと考えられる。