Investigatiou On Germplasm Resources Of Stevia Rebaudiana(Bertoni) Hemsl.and In Vitro Conservatiou Methods

Stevia rebaudiana(Bertoni)Hemsl.is a perennial herb of the genus Stevia in the family Asteraceae.Because the leaves are rich in various steviol glycosides and are a low-calorie,healthy sugar source,they are used in a variety of industries.Due to the mixed status of some stevia varieties on the market,the quality of the seeds is also high or low,resulting in poor genetic stability of the offspring,there are certain defects,and the total content of glycosides is low,so how to improve the reproduction of stevia Coefficient,maintaining its excellent traits,breeding new varieties with high stevioside content and excellent traits have become an urgent need for stevia production.In this study,7 cultivars of Stevia rebaudiana were collected,and their growth indexes,such as plant height,leaf length,leaf width,leaf spacing,branch,plant weight,fresh leaf weight and dry leaf weight,were observed under the same cultivation condition.At the same time,7 cultivars of Stevia rebaudiana were preserved in vitro,and aseptic rapid propagation system was established and established with stem segments of Stevia rebaudiana buds as materials On this basis,we used Stevia variety 6 as the experimental material to study the etiolation of its tissue culture seedlings,so as to improve the multiplication coefficient of Stevia,select new Stevia varieties with high glycoside content and good characters,carry out industrial scale production and meet the market demand.The results are as follows:1.Through the analysis of the variation of 8 characters of Stevia rebaudiana,it is found that there are differences among different characters of Stevia rebaudiana,and the differences between them are obvious.The variation coefficients of fresh leaf weight and dry leaf weight of a single plant are relatively high,among which the variation coefficient of plant height is the highest(42.08%).Through the analysis of various quantitative characters,it can be seen that there are abundant genetic variations in the whole,indicating that Stevia germplasm has a broad development prospect in the improvement and innovation of new varieties.2.According to the statistical analysis of the characters of St evia rebaudiana,the results show that:the characters of Stevia rebaudiana are different under the analysis of correlation;through the analysis of principal components,it is known that in all the characters of Stevia rebaudiana,the cumulative square difference contribution rate of two principal components accounts for 77.41%of all the contribution rate,of which plant height is the largest contribution rate,and the contribution rate is 58.49%。3.In vitro tissue culture of Stevia rebaudiana showed that:7 different Stevia cultivars were used as experimental materials,Stevia rebaudiana stem segments as explants,MS as basic medium,under the same culture conditions,callus culture,duster bud induction and root growth of different Stevia rebaudiana cultivars were studied.The results showed that the establishment of aseptic propagation,the induction and proliferation of buds and the Rooting Condition of Stevia rebaudiana were different.4.Using Stevia variety 6 as the experimental material,the proliferation and etiolation of Stevia tissue culture were studied.The results showed that the proliferation and etiolation rate of Stevia were affected by sucrose concentration and transfer time.The best subculture of Stevia rebaudiana tissue culture seedlings was in 14d,which could reduce the rate of etiolation to the maximum extent.The growth condition of tissue culture seedlings was also good the rate of etiolation was 18.3%,the most suitable concentration of sucrose to reduce the rate of etiolation was 35g/L,the rate of etiolation was 3.5%,and the growth of Stevia rebaudiana tissue culture seedlings was good.