単胚性カンキツにおけるコルヒチン処理による四倍体の作出とその種子親としての利用による三倍体の獲得(育種・遺伝資源)  [in Japanese] Induced Tetraploid by Colchicine Treatment in some Monoembryonic Citrus Cultivars and Triploidy Production by Using the Tetraploid as Seed Parents(Breeding & Germplasm Resources)  [in Japanese]

カンキツにおいて三倍体育成の交配親となる単胚性四倍体を作出するため,コルヒチン処理した腋芽を接ぎ木する方法により染色体倍数化を行った.その結果,8品種・系統で19個体の四倍体を得た.四倍体が得られた品種・系統は,'大橘','水晶ブンタン','農間紅ハッサク','清見','安芸タンゴール','西之香','ありあけ'および'広島果研11号'であった.作出した四倍体'清見'を種子親として二倍体'大橘'を交配すると,一果実当たりの三倍体獲得数は7.68であり,二倍体'清見'×二倍体'大橘'の0.05,二倍体'清見'×四倍体'大橘'の0.16に比べて,極めて効率よく三倍体が得られた.また,他の単胚性四倍体を種子親とした二倍体との10組み合わせの交配においても,三倍体が効率的に得られ,一果実当たりの三倍体獲得数は,四倍体'ありあけ'では0.47〜0.91,四倍体'日向夏'では2.13〜2.86,四倍体'クレメンティン'では4.25〜6.00,四倍体'清見'では6.79〜11.33であった.この10組み合わせの交配では,主に小粒の完全種子を形成したが,培養すると79.1%が植物体に再生して,そのうち99.8%(487個体)が三倍体であった.

We carried out colchicine treatment of lateral buds and their grafting in some monoembryonic citrus cultivars to induce tetraploid plants. Among the grafted plants, 19 eutetraploid plants were obtained from 8 cultivars. The successful cultivars were 'Ootachibana', 'Suisho-buntan', 'Nouma-benihassaku', 'Kiyomi', 'Aki-tangor' 'Nishinokaori', 'Ariake' and 'Hiroshimakaken No.11'. Then efficiency of triploid production was very high (7.68 triploid/fruit) when the tetraploid 'Kiyomi' were used as a seed parent. The efficiency was higher than those for crossing trials of diploid 'Kiyomi'×diploid 'Ootachibana' (0.05 triploid/a fruit) and diploid 'Kiyomi'×the tetraploid 'Ootachibana' (0.16 triploids/a fruit). In addition, when some other monoembryonic tetraploids were crossed with diploid cultivars, they also bore triploid plants efficiently as seed parents, such as 0.47-0.91 in the tetraploid 'Ariake', 2.13-2.86 in the tetraploid 'Hyuganatsu', 4.25-6.00 in tetraploid 'Clementine', 6.79-11.33 in tetraploid 'Kiyomi'. Although the sizes of the hybrid seeds were smaller than the averaged diploid seeds, but the seeds matured fully and germinated well (79.1%) in vitro. This study showed that 99.8% of the raised hybrid plants were triploid (487 plants).