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No.50 (2003/12) >

 
Title :Oryza rufipogon由来の系統RT18Aにおける細胞質雄性不稔および稔性回復の遺伝
Title alternative :Inheritance of Cytoplasmic Male Sterility and Restoration of Fertility in Rice Line, RT18A, derived from Oryza rufipogon
Authors :本村, 恵二
石嶺, 行男
諸見里, 善一
村山, 盛一
Authors alternative :Motomura, Keiji
Ishimine, Yukio
Moromizato, Zenichi
Murayama, Seiichi
Issue Date :1-Dec-2003
Abstract :細胞質雄性不稔性を用いたイネのヘテロシス育種においては、中国の海南島で発見されたWA細胞質が主に用いられている。しかしこの様な特定の細胞質のみを用いた限定的な利用では遺伝的脆弱性が心配される。その解決のためには、多くの雄性不稔細胞質を発見・同定し、遺伝分析を行って優良素材を探索する必要がある。著者等はその点の研究を進めており、今回次のような研究を行った。Oryza rufipogonのK18系統を1回親母本にし、栽培イネ品種、台中65号を反復親父本に用いて8回の連続戻交雑を行って、雄性不稔系統RT18Aを得た。同系統の花粉は球形であるが正常花粉に比べて小さく、また正常花粉が染色液で濃紫色になるのに対して同花粉は薄い褐色を示した。これらの花粉は活性を持たず、したがって種子稔性も完全不稔であった。この花粉退化の様式は既に報告したRT61C系統のそれと似ており、同系統の稔性回復遺伝子を用いてRT18Aの雄性不稔性の遺伝分析を行い、併せてRT18A系統の細胞質の同定を試みた。両系統および台中65号を材料に用いて交雑実験を行い、以下の結果を得た。稔性は細胞質と核内の稔性回復遺伝子との相互作用により支配されていた。すなわち、正常細胞質(mfc)のもとでは稔性回復遺伝子(Rf^1_1-rf)の優劣に関係なく、花粉が正常に発育し、受精が行われるため種子稔性も正常であった。雄性不稔細胞質(msc_1)のもとでは、Rf^1_1遺伝子を持つ花粉は正常であるが、rf遺伝子をもつ花粉は途中で発育を停止し不稔となった。そのため雄性不稔細胞質のもとでは遺伝子型により花粉および種子稔性が異なった。(msc_1)Rf^1_1Rf^1_1では花粉は球形で濃染し正常であり、種子稔性も正常であった。(msc_1)Rf^1_1rfではRf^1_1花粉は正常であるがrf花粉は不稔であった。種子稔性は、(msc_1)rfrf個体以外は高かった。(msc_1)Rf^1_1rf個体の自殖後代では、不稔個体が生ぜず、配偶体支配型の花粉不稔を示すことがわかった。以上の結果はRT61Cに見られた雄性不稔および稔性回復の遺伝に酷似しており、RT18Aの細胞質はRT61Cのそれと同一の可能性が高かった。しかし、確実な同定のためには他の複数の稔性回復遺伝子との間で示される稔性反応を調べる必要がある。
The usage of limited cytoplasm of crpos is genetically vulnerable. It may cause outbreak of diseases and insects, which attack a particular cytoplasm preferentially. Therefore, it is necessary to develop other sources of cytoplasmic male sterility. In this paper, the inheritance of male sterility and fertility restoration induced by the interaction between cytoplasm and a nuclear gene in rice line will be reported. To develop isogenic lines, K18, a line of Oryza rufipogon, was used as the initial female parent, followed by successive backcrosses to Taichung 65 as the recurrent male parent. In B C_8F_1 generation the male sterile line was developed and designated as RT18A. The line had sterile pollen so that spikelets were also revealed to be sterile. On the other hand, RT61C was also developed by the successive backcross method. It was found that the line carried both male sterile cytoplasm (cms_1) and restoring gene (Rf^1_1) derived from K61C. To clarify inheritance of cytoplasmic male sterility and identify cytoplasm in RT18A, crossing tests were carried out, and the following results on inheritance of cytoplasmic male sterility and restoration fertility were obtained. Fertility was conditioned by the interaction between a pair of nuclear restoring genes, Rf^1_1 and rf, and the male sterile cytoplasm, msc_1. Pollen grains with the Rf^1_1 gene displayed normal development under the msc_1 cytoplasm, while pollen grains with the rf gene degenerated under this cytoplasm. Therefore, the degree of pollen and spikelet fertility in the msc_1 plants varied with the genotype. In pollen fertility, (msc_1)Rf^1_1Rf^1_1 plants showed complete fertility; (msc_i)Rf^1_1rf plants 50% fertility-normal pollen grains and degenerated ones; and (msc_1)rfrf plants complete sterility. In spikelet fertility, both (msc_1)Rf^1_1Rf^1_1 and (msc_1)Rf^1_1rf plants showed a high degree of fertility, while the (msc_1)rfrf plants showed complete sterility. In contrast, in the plants with the male fertile cytoplasm of Taichung 65, mfc, pollen grains developed normally and displayed an equal opportunity of fertilization regardless of their genotype. Pollen grains with the rf gene of the (msc_1)Rf^1_1rf plants could not be used for fertilization and this type of pollen abortion was gametophytic. This mode of inheritance was the same as that observed in RT61C. The abortion of sterile pollen grains also started at an earlier stage of pollen development as RT61A, i. e. the grains were smaller and less stained. It was considered that this stage of pollen degeneration was controlled by the characteristics of cytoplasm. Therefore, cytoplasm of RT18A must be the same as that of RT61A, i. e. msc_1. However, for positive identifiction the more detailed examinations are needed with the use of other restoring lines.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3593
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.50 p.35 -40
Appears in Collections:No.50 (2003/12)

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