マツ類の交雑育種に関する研究 (1) : クロマツの種内交雑ならびに他のマツ類数種との種間交雑の可能性

Abstract

本実験は京都大学上賀茂試験地において, 1961 - 1965年にかけてクロマツを雌性親とした種内交雑と, 数種の外国産マツ類を雄性親とした種間交雑の可能性について行なったものである。その結果は次のとおりである。1) 雌, 雄花の開花時期と交配時期 雌, 雄花の開花は3月からの温度の上昇時期や上昇の程度に深い関係があった。種ごとの雄花の開花はかなり異っていて, Pinus banksianaがもっとも早く, しかも長期間の開花期を有し, ついでP. massoniana, P. luchuensis, P. thunbergii, P. taeda, P. pinaster, P. densiflora, P.rigidaの順に開花したが, 個体間ではかなりの差異がみられた。花粉の発芽率は毎年平均して50 - 90％を示した。袋内の温度は外温にくらべ10 - 15℃たかいことから部分的に雌花の発育を阻害することもあった。交配する時期は花粉飛散最盛期前に数回受粉した方がよいようである。2) 種内交雑 自家, 他家, 無受粉の間において, 自家受粉は他家受粉より種子稔性が低く, 無受粉では結果も少なく, 充実種子はほとんど得られなかった。球果や種子の大きさでは無受粉がもっとも小さく, 自家, 他家受粉間では有意な差はみとめられなかった。3) 種間交雑 クロマツにアカマツ他数種の外国産マツ類を組合せて受粉した結果, 毎年平均して, P. thunbergii×P. luchuensis, ×P. massonianaなどは種子稔性がたかく, 交雑が可能で, 一方×P. pinaster, ×P, rigidaなどはほとんど充実種子が得られず, 交雑が不可能であると思われた。しかし, ×P. taedaや, ×P. banksianaなどは交配年度によっては充実種子が得られる場合があり, この原因については明らかではない。

The experiment was carried out, during 1961 to 1965, to see the degree of intraspecific cross in Pinus thunbergii, and also the cross-ability of interspecific cross, using Pinus thunbergii as the female parent trees, and P. thunbergii, P. densiflora and other six species of foreign pine as the male parent trees planted at Kamigamo Experimental Forest Station of Kyoto University. The outlines of the results were as follows: 1. Flowering period of male and female flowers There were striking difference in the beginning of male flowering by the species, namely, P. banksiana had the earliest one and the blossoms for a long period and the order of flowering was followed to P. massoniana, P. luchuensis, P. thunbergii, P. taeda, P. pinaster, P. densiflora and P. rigida. However, they were some difference among parent trees even in a same species. The beginning of male and female flowers had some relation to the arising period and its degree of temperature. The germination of fresh pollen in these species was about 50 to 90 percent. The temperature of inside pollination bags was higher about 10℃ to 15℃ than the open, so that a part of female flowers was often harmed their development by such high temperature in the bags. 2. Introspecific pollination In the self, cross and non pollination, the seeds fertility of self one was lower than the cross one, and also the seeds set were scarce in non pollination, because the full seeds obtained were few. The size of cones and seeds was the smallest in non pollination as compared with self and cross pollinations and it was no significant in self and cross ones. 3. Interspecific pollination P. thunbergii cross P. luchuensis, P. thunbergii cross P. massonina showed high seed fertility in annual means. On the other hand, P. thunbergii cross P. pinaster, P. thunbergii cross P. rigida few yielded the full seeds because of failure to cross with such two species. In some year of pollination, the full seeds were obtained even in P. thunbergii cross P. taeda, and P. thunbergii cross P. banksiana. However, it is not cleared for these reasons.