マツ属の二葉松類および三葉松類の核学的研究(林学科)
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マツ属の核学的研究は, 種の類縁関係, 系統発生, 進化に関する知見を得るのに役立つだけでなく, 林木育種に関する基礎的研究として重要である。著者は本研究において, まずマツ属の核型分析に適するミクロテクニックを開発し, この方法でマツ属の二葉松類8種, 三葉松類2種の核型を明らかにすることができた。著者の改良した冷・温処理法は, 特に二次狭窄の観察に適当であった。その手順は, 前処理として根端を水の入った管瓶にとり, 48時間氷塊で冷却し, 続いて20∿25℃で1∿2時間温処理を行なうものである。固定には酢酸アルコール(1 : 3)を用い, 60℃の1規定塩酸で解離し, フオィルゲンおしつぶし法でプレパラートを作製した。[table]染色体の形態を数的に表現し, 種間の核型を比較する目的で, 相対長, 着糸点指数, 腕長比およびTF値を用いた。マツ属のすべての種の染色体数は, 例外なく2n=24であることがわかった。それらは染色体の形態的特徴に基づいて, 二次狭窄型, 中部着糸点型および次中部着糸点型染色体の3群にわけ, 各群ごとに長さの順に配列しそれぞれに記号を付した。即ち : 1)二次狭窄型染色体 : SC_1,SC_2,SC_3のように記号する。2)中部着糸点型染色体 : M_1,M_2,・・・, M_7のように記号する。3)次中部着糸点型染色体 : SM_1,SM_2のように記号する。各群に属する染色体数は, 二次狭窄型染色体では2∿3対, 中部着糸点型染色体では7∿9対, 次中部着糸点型染色体では1∿2対で, 種によってそれぞれ異なっていた。本研究においては, 染色体をSC_1,SC_2,SC_3;M_1,M_2,・・・, M_7;SM_1,SM_2の順に配列した。したがって核型式は次のように表示された。(1)二葉松類の核型1)Pinus densiflora S. et Z.=K(n=12)=3SC+7M+2SM 2) Pinus thunbergii Parl.=K(n=12)=3SC+7M+2SM 3) Pinus thunbergii X Pinus densiflora F 1=K(2n=24)=6SC+14M+4SM 4) Pinus luchuensis Mayr=K(n=12)=3SC+7M+2SM 5) Pinus insularis Endl.=K(n=12)=2SC+8M+2SM 6) Pinus pinaster Ait.=K(n=12)=2SC+8M+2SM 7) Pinus echinata Mill.=K(n=12)=3SC+8M+1SM 8) Pinus virginiana Mill.=K(n=12)=3SC+8M+1SM (2)三葉松類の核型9)Pinus elliottii Engelm.=K(n=12)=3SC+8M+1SM 10) Pinus taeda L.=K(n=12)=2SC+9M+1SM上記の核型式で, 3SCはSC_1,SC_2,SC_3を示し, 7MはM_1,M_2,・・・, M_7を示し, 2SMはSM_1,SM_2を示すものである。マツ属各種の染色体の長さ(相対長), 着糸点指数およびTF値について詳細な分析をおこなった結果, マツ属における種の分化は, これまで考えられていたように遺伝子レベルだけでなく, 染色体の構造上の変化も関与していることが推定された。また, それらの値は種特有のものであることがわかった。Karyological study on the genus Pinus should contribute to clear up phylogeny, the process of evolution and interrelation of species in the genus. It is also an important and fundamental field in forest tree breeding. The microtechnique most suitable for karyotype analysis of the genus Pinus was developed by the author, with which clarified was the karyotype of such species as Pinus densiflora S. et Z., P. thunbergii Parl., P. thunbergii X P. densiflora F 1,P. luchuensis Mayr, P. insularis Endl., P. pinaster Ait., P. echinata Mill., and P. virginiana Mill. having two needles, and of such species as P. elliottii Engelm. and P. taeda L. having three needles in a fascicle belonging to the genus Pinus. This microtechnique, which was specifically suitable for observation of the secondary constriction, was as follows : 1) Root tips were transfered into a water-filled glass tube, and cooled for 48 hours by using ice-block. 2) The glass tube was then kept under room temperature of 20 to 25℃ for 1 to 2 hours. 3) Fixation was done in acetic-alcohol (1 : 3) for 1 to 2 hours. 4) The root tips were hydrolyzed in normal HCl for 8 to 10 minutes at 60℃. 5) The preparation of chromosomes were made by Feulgen squash method. Relative length, centromeric index and TF values of the chromosomes were emplyoed in order for comparison of karyotype and for numerical expression of morphology of the chromosomes. The chromosome number of all species belonging to the genus Pinus was found to be 2n=24 without any exception. The chromosomoes were classified into three groups based on their morphological feature as follows : 1) The first group was of the chromosomes with secondary constriction as symbolized by SC1,SC2,and SC3.2) The second group was of those with median constriction as symbolized by M1,M2,..., and M7. 3) The third was of those with submedian constriction as symbolized by SM1,and SM2. Each group had different number of chromosomes. Namely, two or three pairs of chromosome were found in the first group with secondary constriction, 7 to 9 pairs in the second group with median constriction, and 1 or 2 pairs in the third group with submedian constriction. The number of chromosome in the respective group varied by the species. In the present paper, the chromosomes were arranged in the order of SC1,SC2,and SC3; M1,M2,..., and M7; and SM1,and SM2,so that the morphological features of chromosomes could be emphasized. Accordingly, the karyotype formulas were established. The formulas for pine species having two needles in a fascicle were as follows : 1) Pinus demsiflora S. et Z. =K (n=12)=3SC+7M+2SM 2) Pinus thunbergii Parl. =K (n=12)=3SC+7M+2SM 3) Pinus thunbergii X Pinus densiflora F 1 =K (2n=24)=6SC+14M+4SM 4) Pinus luchuensis Mayr=K (n=12)=3SC+7M+2SM 5) Pinus insularis Endl. =K (n=12)=2SC+8M+2SM 6) Pinus pinaster Ait. =K (n=12)=2SC+8M+2SM 7) Pinus echinata Mill. =K (n=12)=3SC+8M+1SM 8) Pinus virginiana Mill. =K (n=12)=3SC+8M+1SM For pine species having three needles in a fascicle; 9) Pinus elliottii Engelm. =K (n=12)=3SC+8M+1SM 10) Pinus taeda L. =K (n=12)=2SC+9M+1SM In the above formulas, for example, 3SC stood for SC1,SC2,and SC3; 7M for M1,M2,..., and M7; and 2SM for SM1 and SM2,respectively. Detailed analysis on the relative length, centromeric index and TF values of chromosomes suggested that the specialization of species in the genus Pinus was participated not only in the genic level but also in structural changes of chromosomes. It was also found that each species of the genus Pinus was characteristic of the relative length, centromeric index and TF values of chromosomes.
- 琉球大学農学部の論文
- 1975-12-01
琉球大学農学部 | 論文
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