サツマイモ(Ipomoea batatas(L.)Lam.)の同一交配不和合群内品種間の体細胞雑種の作出 Production of Somatic Hybrid between Cultivars of Sweet Potato, Ipomoea batatas(L.) Lam. in the Same Cross-incompatible Group

サツマイモ(Ipomoea batatas(L.)Lam.)の交配不和合品種間の体細胞雑種の作出に成功した。交配不和合な2品種(B群)コガネセンガンとBitambiのプロトプラストをPEG法により融合処睡後,O.05mg/l2,4-DとO.5mg/lkinetinを含む1/2修正MS液体培地に置床して培養した。形成した1〜2mmのカルスを2,4-DとkinetinあるいはABAを,又はNAAとBAPを添加したMS固形培地に移植した後,植物ホルモンフリー培地で培養した。培養した393個のカルスから45個体が再生した(Fig.1)。形態的特徴,染色体数及びDNA多型(RAPD)等の分析によって,2個体の再生植物体が体細胞雑種であることを確認した。葉形と頂葉色は融合両親の中間の特性を示し,染色体数は両親の和であった(2n=12x(2n+2n)=180)(Tab1e 1,Figs.2,3)。RAPD分析を行った結果では,融合両親の一部バンドを合わせ持ち,しかも両親には認められないバンドも有していた(Fig.4).圃場での生育は悪く(Tab1e 1),キダチアサガオに接木して誘導した花は奇形で,花粉稔性率はO及び12.2%であった。また,サツマイモ品種九州30号(C群)の花粉を受粉しても種子は得られなかった(Tab1e 1)。

This is the first report on successful production of somatic hybrid between cross-incompatible cultivars of sweet potato, lpomoea batatas (L.) Lam. The protoplasts of sweet potato cultivars, Koganesengan and Bitambi, belonging to the same cross-incompatible B group and not crossing with each other, were fused with Polyethylene Glycol (PEG) solution and then cultured in modified liquid MS (Murashige and Skoog 1962) medium containing 0.05 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) and 0.5 mg/l kinetin. Forty-five plants were obtained from the calli on the hormone-free medium by using the callus proliferation medium either supplemented with 2,4-D and kinetin or abscisic acid (ABA), or supplemented with naphthalene aceic acid (NAA) and 6-benzylaminopurine (BAP). Two plants were considered to be the somatic hybrids by analyzing their morphology, chromosome numbers and random amplified polymorphic DNA (RAPD) markers. The hybrids showed intermediate characters in leaf shape and leaf color between the two parents and had chromosome numbers that correspond to the sum of their parents (2n= 12x (2n+2n)= 180). By RAPD assay, they expressed some of the bands from both parents. They grew slowly in the field. One of them had the pollen fertility of 12.2 % when grafted on the morning-glory for flower induction. No seed was obtained by crossing with pollen of Kyushu No. 30 (cross-incompatible C group cultivar).