Studies On Factors Of Influencing Somaclonal Variation Frequency In Populus

Poplar is a group important timber species especially in industries, and it is widely cultivated in middle latitude region. At present, it has become the mostly researched tree species in tissue culture and biotechnology breeding. Although a plenty of research results have shown that it is universal that somaclonal variation appeared in Populus, many of them were superficiality. The most of them only find out the phenomenon of somaclonal variation. Though some others have reported factors of influencing somaclonal variation, their researches were not systemic. The variation causes haven't been researched completely. Thus it is necessary to research the factors of influencing somaclonal variation in Populus systematically. Populus hopeiensis and Populus alba were choosen as representative species in this research, because they are widely distributed in northwest China and the tissue culture techniques of them are quite well. To obtain regenerated plantlet, one test-tube seedling of two species were chosen respectively as starting materials, different kinds and concentration of growth regulators were added in culture medium, and test-tube seedlings were cultivated by different regeneration methods and in different times. To research factors of influencing somaclonal variation frequency in Populus, DNA were extracted from the tender leaves of regenerated plantlet and variation frequencies in DNA level were detectd by RAPD method. The main results are as below:(1) The influencing of growth regulators on somaclonal variation frequency: 0.005～0.015 mg/L TDZ and 0.5～1.5 mg/L ZT were added in culture medium respectively, and somaclonal variation frequency of Populus hopeiensis and Populus alba couldn't be detected after regeneration. Although 0.10～0.20 mg/L 2, 4-D made no difference on variation frequency in two species of poplar after one time of subculture, the variation frequencies in plants and locus level increased with enhancing of 2, 4-D concertation after three and five times of subculture. The maxium of variation frequency in plants and locus level were 25.00% and 5.36% in Populus hopeiensis, and 20.00% and 4.46% in Populus alba, respectively. (2) It is more obvious that the appearance of somaclonal variation in Populus hopeiensis and Populus alba by inducing callus to gain regenerated plantlet than by approach of direct organogenesis. In this study, the variation frequencies in plants and locus level couldn't be detected in two species of poplar by the latter approach. However, by the former one, the total variation frequency in plants and locus level in Populus hopeiensis were 13.33% and 5.36%, and 11.67% and 5.26% in Populus albe, respectively.(3) The variation frequency in plants and locus level in Populus hopeiensis and Populus alba increased with times of subculture in 0.15 mg/L and 0.20 mg/L 2, 4-D. In whatever 2, 4-D concertation, there was no variation in two species of poplar. But, after five times of subculture, in 0.15 mg/L 2, 4-D, the variation frequency in plants and locus level were 10.00% and 1.80% in Populus hopeiensis, and 10.00% and 1.79% in Populus alba, respectively; in 0.20 mg/L 2, 4-D, they were 25.00% and 5.36% in Populus hopeiensis, and 20.00% and 4.46% in Populus alba, respectively.(4) In total, after different times of subculture, 2, 4-D can induce variation in two species of poplar. The variation frequency in plants and locus level in Populus hopeiensis was higher than in Populus alba. Therefore, it is more obvious that the appearance of somaclonal variation in Populus hopeiensis than in Populus alba.