トウガラシ本葉からの不定芽形成に及ぼす培養条件の影響

Effect of culture conditions on in vitro induction of adventitious buds from leaf explant was studied in pepper cv. 'Shosuke' (Capsicum annuum L.), to establish mass propagation method of genic male sterile line, 'ms-Shosuke', which is in practice used for hybrid seed production. Left explant was trimmed from aseptically grown seedling, and a proximal quarter part of the leaf along with a small portion of petiole was placed on MS agar medium with the proximal cut end embedded in the medium. The cultures were kept at 27℃, and illuminated for 16 hours per day (3000 lux). Leaf explants trimmed from 30 days old seedlings were inoculated on MS media supplemented with different concentrations of zeatin and casein hydrolysate (Table 1), and of BAP and IBA (Table 2). Adventitious buds were induced at high frequency on all of the culture media. Among them the following media were recommended: one to be supplemented with 3mg/I zeatin and 100mg/I casein hydrolysate, and the other with 3~5mg/I BAP and 0.2mg/I IBA. Physiological age of leaf explant, which was expressed as seedling age, proved to be a crucial factor to determine differentiation ability. Average number of adventitious buds induced from an explant was more than 12, when the explant was trimmed from 25 days old seedling (Table 3). IT was therefore concluded that just unfolded young leaf should be used as explant. To promote the development of shoots from adventitious buds, the cultures were transferred to MS medium supplemented with 1mg/I zeatin. Then well developed shoots were dipped in 1mg/I IAA solution for three days and aseptically grown on vermiculite, resulting in the establishment of plantlets with roots. Although rooting occurred in all shoots, the efficiency of shoot development from adventitious buds was only 21% in the best case (Table 4). Therefore the culture method must be further improved to increase efficiency.

組織培養法を利用した雄性不稔系統の大量増殖法を開発するために、トウガラシ本葉からの不定芽形成に最適の培養条件について検討した。実験にはトウガラシ品種'昌介'を供試し、初生葉の基部側1/4を葉柄の一部を付けて切り出した切片を外植体として以下の実験を行った。　1.発芽後30日苗の本葉切片を用いて不定芽誘導培地の組成について検討した。その結果、ゼアチン3mg/ℓ+カゼイン加水分解物100mg/ℓ,もしくはBAP 3~5mg/ℓ+IBA0.2mg/ℓを添加した培地が適用していることが明らかになたった。2.上の実験で明らかになった好適培地(BAP 5mg/ℓ+IBA 0.2mg/ℓ)を用いて、発芽後25~60日苗の初生葉を培養した。その結果、25日苗では外植体あたり12.7個の不定芽が形成されたが、苗齢とともに不定芽形成能が低下することが明らかとなった。3.以上の結果より、展開直後の若い本葉を上記2種類の培地に置床すれば、多数の不定芽が形成されることが明らかとなった。ただし、不定芽のうち植物体にまで生長したのは約2割と低頻度であったので、培養法の更なる改善が必要と考えられる。