The Study On Polyploid Induction And Biological Characteristics Of Stevia Rebaudiana Bertoni

The seeds of Stevia rebaudiana strain ‘7330’ and the aseptic stem sections of Stevia rebaudiana‘Waiyin2’ were induced by different concentrations of colchicines for different time treatments, thenautotetraploid plants were confirmed based on morphological characters, stomatal sizeand chromosomedetermination. The studycompared morphological characters, stomatal index, thenumber ofchloroplastand chlorophyll relative content of diploid and autotetraploid plants, and analysised SrKO、SrKA13H、SrUGT85C2、SrUGT76G1、SrUGT74G1gene’s relative expressions of Stevia rebaudianadiploid and autotetraploid plants by Quantitative Real-Time PCR, to explore the influence of the ploidyto gene expression in control of glucoside component synthetic. Research on Stevia rebaudianapolyploidy breeding is of great significance for raising the production of Stevia rebaudiana.The mainresearch results as following:(1)The seeds immersed in0.3%colchicines solution for24h prior to culture induced as high as11.63%, and the stem sections in0.1%colchicines solution for48h prior to culture induced as high as32.5%. The two methods show that the effects of high colchicinessolution forshort term or lowcolchicines solution for long term were better than others. It earned a total of13autotetraploid plants bythe first method, it got a total of45autotetraploid plants by the second.The inductive effect of thesecond method is better.(2)On the morphology, the autotetraploid plants growed slowly with deeper green andmoredistorted leaves. The blade’s width, thickness, weight and inflorescence of autotetraploid plantswere significantly greater than the diploid.On the cytology, its guard cells and stomatal size showedlarger, and the number of chloroplasts increased significantly, but the stomatal density reduced. Thechromosome number of diploid cells was2n=22, autotetraploid cells was2n=44, chimera cells were2n=22and2n=44. On the physical characteritics, autotetraploid plants had chlorophyll relative contentobviously higher than diploid plants. These characteristics can be used as methods for ploid contentyidentification.(3)At the molecular level, the relative expressions of SrKO、 SrKA13H、 SrUGT74G1gene in theautotetraploid plants were higher than in the diploid, but SrUGT85C2、SrUGT76G1gene’s relative expressions in the autotetraploid plants were lower than the diploid, so it suggested that the geneexpression show various pattern between in autotetraploid plants and diploid plants.