Bilolgical Characters And Genetic Variation Study On Diploid And Autoteraploid Stevia Rebaudiana Bertoni

Stevia rebaudiana Bertoni is a perennial herb native to South America sugar crops,in Paraguay and Brazil at the junction of the alpine grassland area,it contains the sweetness of stevioside is 250-300 times than sucrose,but the calories just 1/300.which Now replace saccharin is widely used in food,pharmaceutical and other industries,and is recognized internationally as the "world's third healthy sugar source".In recent years,due to the stevia varieties seriously degradated,yield and stevia glycoside content lowed,conventional breeding difficultly solved this problem.while the induced autopolyploid can improve the yield and active ingredients contentions of medicinal plant,we through the tissue culture combined with colchicine induced mutation,obtained stevia autotetraploid in vitro.In this paper,The autotetraploid Stevia Rebaudiana Bertoni and diploid Stevia Rebaudiana Bertoni as experimental materials were comparatively studied by Morphological characteristics,Photosynthetic Characteristics,stevioside content and genetic variation.For the stevia polyploid breeding provide theoretical application and practical basis.Details and results are as follows:1.The study is to compare the mechanism of apparent traits,Photosynthetic Characteristics and Active ingredient content of Stevia Rebaudiana Bertoni Autotetraploid and diploid,The result showed that Stevia tetraploid plant stems stout,leaf thickening,leaf area increases and plant becomes shorter,The Photo synthetic Characteristics,such as net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),were significantly higher than those of diploid.The stevia tetraploid light compensation point(LCP),apparent quantum efficiency(AQY)and CO2 compensation point(CCP)were respectively increased by 28.66%,1181.81%,11.74%than the diploid,while its light saturation point(LSP),dark respiration rate(Rd)and carboxylation efficiency(CE)were significantly lower than those of diploid.Stevioside content of stevia tetraploid(13.212%)was improved by 24.32%than the diploid(9.998%),of which the major component of stevioside rebaudioside(RA)and rebaudioside(RC)were significantly higher than that of diploid.This indicates that afther stevia doubling,plant morphology,photosynthetic characteristics and stevioside content generated significant difference,which is for the further studies of stevia polyploid breeding and lay the foundation for exploring the biological characteristics and quality of stevia polyploid.2.The research used AFLP and ISSR technique to analyzed the genetic variation of Stevia rebaudiana Bertoni diploids and autotetraploids.AFLP results showed that,in 25 pairs of 681 primer combinations amplified bands,198 bands were polymorphic,the polymorphic rate was 29.07%.in the level of ISSR,5 primers which could produce polymorphic and steady bands,screened out of 60 random primers,were used and produced 34 bands totally.Of them 19 bands(55.88%)were polymorphic;The genetic diversity index between 0.0059-0.4236 in 6 lines of Stevia;The UPGMA dendrogram suggested that diploids and autotetraploids Stevia were separated well for CK and 5 separated firstly and the genetic similarity coefficient of 1 and 2 lines,4 and 5 lines were high.there was significant genetic variation between autotetraploid and diploid Stevia,The different lines of autotetraploid Stevia also have genetic variation.