Studies On Chromosome Doubling Of Populus×euramericana Cv. 'nanlin895'

Chromosome doubling of poplars is important and significant both in species evolution and mutantion breeding. In this paper, Populus×euramericana cv. 'Nanlin895' was used in germfree condition as initial explants. Leaf disc, leafstalk, node stem were used as final explants. We used different basis media, given different concentration of colchicine, studied buds induce and reproduce and dealt with the ploidy level of the plants. The major conclusions as following:1. The optimal conditions for inducing tetraploids were under adopting leaf discs for 3d in the dark with colchicine at a concentration of 2% after pre-culturing for 3d, then adopting leaf discs for 3d in light. The rate of induction was 18.75%.2. The results indicated that the root induction went down and the explant browning rates increased as the colchicine concentration increased. The optimal explant was leafdisc. The optimal conditions for inducing root were: adopting germfree colchicine to treat explants for 3d in the dark after pre-culturing the explants for 3d, then adopting leaf discs for 3d in light. The optimal conditions for the least explant browning rate were adopting germfree colchicine to treat explants for 3d and 7d after pre-culturing the explants for 7d with leafstalk at a concentration of 0.5%.3. A lot of abnormal roots and tube plants were observed, showed the harmfulness of colchicine. The results showed the explant browning rate increased as the colchicine concentration increased. Moreover, the harmfulness increased as the colchicine concentration increased. Almost all of the regeneration plants died with colchicine at a concentration of 5%.4. Ploidy levels were determined by several methods: somatic chromosome counting, leaf stomata size and certain plant morphological characteristics. The results indicated that chromosome counting was the most reliable and precise method. Leaf stomata size of tube plants treated with colchicine were larger than the ones of CK, which can be considered as one of the characteristics of morphology and anatomy and an index of tube plant of autotetraploid.5. Study on chromosome sample preparing in the poplars: the number of chromosomes brought about difficulties. Parameters and technique of chromosome preparing were studied, and a suitable method was established. This paper summerized the precautions in chromosome sample preparing. All of these offered solid foundation for further experiment. Determination of selective parameters: cutting the roots or buds whenever you want, putting the material for 24-48h in ice water; then in carnoy's over 24h , 4℃; finally in 65℃HC1 for 7min.