Polyploid Induction And Salt Tolerance Of Stevia Rebaudiana

Nowadays,with the rapid development of economy and the continuous improvement of quality of life,more and more polysaccharides have been ingested.The resulting diseases,such as hyperglycemia,hyperlipidemia,hypertension,obesity and so on,are also becoming more and more popular.This requires us to choose a-substitute of meet people’s needs for sweetness,while reducing the intake of sugars.Stevia rebaudiana is a kind of plant with high sweetness and low sugar content.The sweetness of stevia sugar extracted from Stevia rebaudiana is 300 times that of sucrose,but its sugar content is only 1/300 of that of sucrose.The following experiments were carried out for the successful introduction of Stevia in Tianjin and the breeding of better quality Stevia.(1)In this experiment,Stevia was used as material,and four varieties of Stevia including‘Run De’,‘Jiao Long’,‘Pu Xing 3’ and ‘Shou Tian 1’ were treated with different concentration gradient salt stress.The physiological and biochemical indexes of four varieties of Stevia rebaudiana were determined and statistically analyzed.The four varieties were evaluated comprehensively with the membership function value of fuzzy mathematics.The results show that:Under salt stress,the content of Proline,malondialdehyde content,soluble sugar content,soluble protein content,superoxide dismutase activity,peroxidase activity in 4 varieties of Stevia showed the trend of increasing and then decreasing with the increase of salt stress.Combined with the survival status of 4 varieties of stevia under salt stress and the analysis results of membership function,we concluded that the tolerance of four varieties of stevia to salt stress is as follows: ‘Run De’> ‘Jiao Long’ > ‘Pu Xing 3’ > ‘Shou Tian 1’.(2)The seeds of “Xin Feng 3” of Stevia were induced to obtein tetraploid by seed impregnation and tissue culture respectively;Plant morphology,stomata,chromosomes and DNA content of diploid and tetraploid were compared and analyzed.We concluded that:The tetraploid Induction rate of Stevia rebaudiana germinated seeds soaked with 0.1%colchicine for 24 hours was the highest,up to 24%.When the seeds of Stevia were cultured in MS medium with 0.025% concentration of colchicine,the induction rate of tetrapioid was 4.44%.Thus,the best effect of polyploid induction with colchicine treatment is either treated short time in high concentration or longtime time in low concentration.Compared with diploid plants,the leaves of tetraploid plants were larger and thicker.DNA analysis showed that each diploid and tetraploid had a single peak,the peak of tetraploid was twice that of diploid.The chimera has both peaks of tetraploid and diploid.The root apical chromosome identification showed that the chromosome number of diploid is2n=22,tetraploid plants is 4n = 44,and chimera plants are 2n = 22 and 4n = 44.