タケ類の育種学的研究 : Bambusa arundinacea および Phyllostachys edulis のX-線, その他の処理が種子の発芽と生長におよぼす影響ならびにマダケ (再生竹) ほか3属4種の交雑について

Abstract

本実験はインド産Bambusa arundinaceaの乾燥種子を用い, 突然変異の誘発, 倍数体の創成, 発芽促進の目的で, X線処理, コルヒチン処理および温度処理を行ない, 種子の発芽率, 幼苗の初期生育調査, さらに生育場所毎の調査を行なった｡ またモウソウチク種子についてもBambusa arundnacea種子と同様の目的で, X線処理, コルヒチン処理および低温処理を行なった｡ またマダケ (再生竹), ヤダケ, タイミンチク, ヒメシマダケおよびスズコナリヒラ間の二面交配を行なった｡ さらにマダケ (再生竹) およびヒメシマダケについて花粉母細胞の成熟分裂を観察した｡ その結果を要約すると次のとおりである｡ 1) Bambusa arundinaceaの乾燥種子のX線照射による発芽率は2kr--14krまでは線量の増加に殆ど影響がなく, 16krからは発芽率が低くなり, 18krで急激に低下し, 28krで発芽不能を示した｡ 2) 初期の生育調査について, 稈長, 葉数はおのおの照射区の方が, 対照区よりもわずかに小さい傾向がみられた｡ 分蘗数において18kr区は他の照射区および対照区よりも少なかった｡ 生育地毎における, 稈長, 分蘗数, 葉数, 葉色および茎色の調査の結果, おのおの個体によってそれぞれことなり, 変異が大きく, X線の直接影響によるものか断定出来ない｡ 3) Bambusa arundinacea乾燥種子のコルヒチン処理は0.2% (48時間) 区および0.4% (48時間) 区とも発芽率は低かった｡ 0.4% (48時間) 区のなかでとくに対照区よりも気孔の大きい, 気孔の分布数の少ない形態的にみて倍数体らしき1個体が観察された｡ 4) Bambusa arundinaceaの低温処理したものは対照区よりも発芽率は, 良好であった｡ 低温処理後高温処理したものは対照区よりも発芽率は低かった｡ 5) モウソウチク種子のコルヒチン処理した, 0.2% (24時間) 区のなかで対照区よりもわずかに気孔の大きい, また気孔の分布数の少い1個体が観察された｡ 6) モウソウチク種子の低温処理 (5℃, 100日間) は発芽は殆どなく, 現在は1個体が生存し, 生育観察中である｡ 7) 交雑試験についてはおのおの組合せとも得られた種子は殆ど粃であったが, これらの交雑のなかで, ヒメシマダケ (♀) ×ヤダケ (♂) で2粒 (内1粒, しわ), ヒメシマダケ (♀) ×スズコナリヒラ (♂) で1粒 (やや粃) を得た｡ その他ヒメシマ間の同系交配 (2粒), 自殖 (2粒), タイミンチ間の同系交配 (1粒), 自殖 (1粒), ヤダケの同系交配 (3粒), 自殖 (1粒) を得た｡ 得られたF1種子は発芽しなかった｡ 8) マダケ (再生竹) およびヒメマシタケの花粉母細胞における成熟分裂を調査した結果いずれも中期核板に24個の2価染色体を観察した｡ 第二分裂も異常はなかった｡ 本研究にさいして栽植管理, 生育調査などについて琉球大学農家政工学部大山保表教授, 鹿児島市立工芸研究所浜田甫氏ならびに東京農業大学育種研究所長近藤典生博士らの協力に対し深甚の謝意を表する｡ また標本作製などに協力していただいた菊地次雄氏に厚く御礼申し上げる｡

With the purpose of making a basic study of the breeding of bamboo and of considering the application of the results of the study, investigations were conducted in the present experiments in respect to Bambusa arundinacea indigenous to India, and Ph. reticulata (Regeneration bamboo) and four genera and six other species indigenous to Japan. Dry seeds of Bamdusa arundinacea were irradiated by X-ray for inducing gene mutation and were treated with colchicine for making poliploids and also were treated by low temperature for promoting germination and raising germination rate, and some of them were treated high temperature after low temperature treatment. Conditions of growth at the initial stage and different places were investigationed. X-ray irradiation, colchicine treatment, and low temperature treatment were also given to the seeds of Ph. edulis for the same purpose. Crossing experiments were also performed on dial crosses between the Ph. reticulata (Madake, regeneration bamboo) and three genera and four species of bamboo, in the Experimental Forest Station of kyoto University. Furthermore, observations were made on the meiotic division of pollen mother cells in respect of Ph. reticulata (Madake, regeneration bamboo) and Pl. angustifolius. The results of the experiments are summarized as follows: 1. The following five genera and seven species were used for the present experimnt; Bambusa arundinacea, Phyllostachys reticulata C, Koch: (Madake, regeneration bamboo), Phyllostachys edulis Riv. (Moso-chiku), Pleioblastus angustifolius Nakai; (Himeshima-dake), Pleioblastus gramineus Nakai; (Taimin-chiku), Pseudosasa japonica Nakai; (Yada-ke), and Sinobambusa tootsik MAK. f. albo-striata Muroi; (Suzukonarihira). 2. The results of X-rays irradiation on dry seeds of Bamdusa arundinacea turned out to be as follows: although there was not much variation in germination percentage from 2Kr to 14Kr, the percentage began to fall from 16Kr onward, and showing a sharp decline at 18Kr, germination came to a total stop at 28Kr. For the number of tillers in each irradiation section, the average number in 18Kr section was found to be fewer in comparison with other irradiation section or the control. Nor much difference was seen among all the irradiation sections as to the length of culms and the number of leaves, but an inclination was observed that the number of leaves was slightly fewer and length of culms shoter in all the irradiation sections as compared with the control. The growth at the initial stage at different places showed a wide variation in each character both in the irradiation sections and in the control. These characters also vary markedly according to each individual. It is not clear whether this is due to indirect effect of X-ray irradiation or not. 3. In the colchicine treatment of dry seeds of Bambusa arudinacea, the germination percentage was found to be extremely low when the seeds had been soaked for 48 hours both in the cases of 0.2% and 0.4% solution. An individual was found in the 0.4% colchicine treatment, however, that seemed to be a polyploid with larger stomata and a smaller number of stomata than the control. 4. Germination percentage was found slightly better when seeds were subjected to low temperature treatment than the control. 5. Those that had undergone high temperature treatment after low temperature treatment showed lower germination percentages than the control. 6. In the colchicine treatment of seeds of Ph. edulis, the germination percentage was found to be low when the seeds had been soaked for 0.4% solution both when 24 hours and 48 hours. 7. In the low temperature treatment of seeds of Ph. edulis, germination was found to be extremely low due when the seeds had been treated for 100 days. At present only one plant is alive. 8. In the diallel crossing among Ph. reticulata (Madake, regeneration bamboo), Pl. angustifolius, Pl. gramineus, Ps. japonica and Si. tootsik f. albo-striata, seeds obtained were mostly shrivelled. Among the crossings, however, two set seeds (seed F1) were obtaind from the mating between Pl. angustifolius (Himeshima-dake) and Ps. japonica (Ya-dake), and one set seed from the mating between Pl. angustifolius (H imeshima-dake) and Si. tootsik f. albo-striata (Suzukonarihira), and also two set seeds from the inbreeding of Pl. angustifolius (Himeshima-dake) and two set selfings, one set seed from the inbreeding of Pl. gramineus (Taimin-chiku) andone set seed selfing, and three set seeds from the inbreeding of Ps. japonica (Ya-dake) and one set seed selfing were obtained. 9. As the result of observation on the maturation division of pollen mother cell Swith the Ph. reticulata (Madake, regeneration bamboo) and Pl. angustifolius (Himeshima-dake), 24 bivalent chromosomes were found in the polar view and side view of the metaphase of the meiotic division.