マツ属の種間交雑からみた種の類縁関係とF_1雑種の生育状況について

Abstract

本論文はマツ属の種間交雑の可能性から, 種間での生殖的隔離と地理的隔離を考慮して類縁関係を再検討し, さらに, 近年わが国におけるマツ枯れ被害対策と関連して, 創出されたF_1雑種の抵抗性やその生育状況について論議した。1. 種間交雑はマツ属の分類学上の亜節内では成功例が多く, 亜節間での成功例は僅かで, 種の生殖的隔離と分類学上の位置付けはほぼ符合した。しかし, 同じ亜節内において交雑の失敗例があり, 地理的な隔離等を考慮するといくつかの種群に区分することが可能であった。Sylvestres亜節は, アメリカ東部に分布する種とヨーロッパ地域に分布する一部の種群, 地中海沿岸地域に分布する晩成球果種群, 東アジア地域に分布する種群およびP. merkusii (1種) の4グループに細分できた。Australesでは, 成熟球果が閉果 (晩成球果) の種群と開果の種群に区分され, Contortaeでは地理的に隔離する2種群, さらにOocarpaeではメキシコ地域とアメリカ西部地域の2種群に区分できる。これらの区分は種分化と密接に関係するものと理解された。2. 上賀茂試験地で創出された雑種は, P. thunbergiiを雌性親とした種間で8種, P. densifloraとの種間で1種, P. taeda × P. rigidaの両面交雑の2種, P. viginianaとの種間で1種, P. muricataとの種間で2種の合計14種である。これらの雑種の中でマツ枯れ被害に対する抵抗性種と考えられるものは, P. taeda × P. rigidaの両面交雑種及びP. virginiana × P. clausaがあげられる。わが国の在来種との間ではP. thunbergii × P. tabulaeformisが抵抗性を示しており今後の生育が期待される。

This paper dealt with the interspecific hybridization, new classification of some subsections of the hard pines based on the possibility of them, and natures on the growth of the hybrids were examined for damage of namatode and margaroid scale in Kamigamo Experimental Station at Kyoto City. 1. The hybrids obtained from the interspecific hybridizations were mainly restricted to the combinations of species in intra-subsection, though many combinations failed in them. This result means correspondence with the reproductive isolation among species and taxonomical classification in the subgenus Pinus. Taking account for the results of reproductive isolation and morphological characters, some subsections were divided into groups or series of species as shown in Table 1. In subsect. Sylvestres, pines are divided four groups, namely, pine species of Eastern America and Europe (Group I), serotinous cone species of Mediterranean region (Group II), pines of Eastern Asia(Group III) and P. merkusii of southeastern Asia (Group IV). Pines of subsect. Australes are divided into two groups of serotinous cone (Group I) and non-serotinous cone species (Group II). Pines of subsect. Contortae are divided into two groups of Northern (Group I) and Southern region (Group II). Pines of subsect. Oocarpae are divided into two groups of Mexico (Group I) and Western America (Group II). These subdivision of pine groups may show the new speciation in them. 2. By the interspecific hybridization at Kamigamo Experimantal Station, 14 hybrids as shown in figure 1 were obtained. The resistance for damage by nematode, Byrsaphelenchus xylophilus, and margaroid scale, Matsucoccus matsumurae, were examined in young trees in these hybrids. Three hybrids of P. taeda×P. rigida, P. rigida×P. taeda and P. virginiana×P. dausa showed the resistance in them. One hybrid of the native pine, P. thunbergii×P. tabulaeformis, have the same nature to the nematode. It may be expected for breeding species in Japan, especially for the coastal forests.