Genetic Diversity And PEBP Gene Family Identification And Expression Analysis Of Stevia Rebaudiana

Stevia rebaudiana is a perennial herb in the Compositae family whose leaves are rich in stevia glycosides.Stevia glycosides are a low-calorie,high-sweetness natural sweetener that is one of the raw materials for pharmaceutical and food processing.Our country is a big country of stevia production and export,at present,there are some problems in stevia germplasm resources,narrow genetic base and variety degradation,so it is still the focus of breeding stevia with high glucoside content and high yield.In this study,seven stevia varieties were used as experimental materials,and the genetic diversity of different varieties of stevia was analyzed by combining agrological traits such as plant height,crown width,branch number and ISSR molecular markers.At the same time,the PEBP gene family of stevia was identified and analyzed by bioinformatics technology.This study provides a reference for further studying the molecular mechanism of stevia flowering regulation and plant structure,The main research results are as follows.(1)The results of agronomic traits showed that the genetic diversity of stevia germplasm resources,The coefficient of variation of branch number was as high as 50.30%.Correlation analysis showed that crown width was positively correlated with stem thickness,number of branches,leaf length and leaf width at the level of 0.01.Principal component analysis showed that the cumulative contribution rate of the eigenvalues of the two principal components was 61.567%,which contained all the information of the six agronomic traits.Phenotypic clustering analysis showed that seven stevia strains could be clustered into four categories at the Euclidean distance of 5.0.The first class were Zhongshanliuhao,Huinongsanhao and Yuanyeyihao;The second class were Shiba and Puxinliuhao;The third and fourth class were RCxinpin and Sanjie respectively.(2)ISSR molecular marker analysis showed that 21 primers were used to amplify the genomic DNA of seven stevia cultivars,and a total of 140 bands were amplified,including108 polymorphic bands,with a polymorphism ratio of 77.1%.At the species level,Shannon information index(I)was 0.4185,and Nei’s gene diversity index(He)was 0.2776,showing high genetic diversity.The genetic similarity of the seven stevia cultivars ranged from 0.58 to 0.86,and they could be clustered into three groups at the level of 0.692.Sanjie,Shiba,Yuanyeyihao and Zhongshanliuhao belonged to first group.Huinongsanhao and RC xipin were catergorified into the second group,and Puxinliuhao were ciustered into group three.(3)Eight PEBP genes were detected from the stevia genome database by bioinformatics methods,which could be divided into two subfamilies: FT and TFL1.It was localized on four chromosomes and its molecular weight was small,mainly between 18.98 and 21.55 k Da,and most of them were basic proteins.All are typical structural features of the PEBP gene consisting of four exons and three introns.The results of promoter element analysis showed that the promoter elements of PEBP gene were mainly light-responsive elements and hormone-responsive elements.q PCR analysis showed that there were significant differences in the expression of Sr PEBP gene in the six tissues detected,for example,Sr TFL1-1 was highly expressed in roots and flowers,Sr CEN was highly expressed in leaves,Sr FT2 and Sr FT3 were highly expressed in flowers and flower buds,Sr FT4 was highly expressed in flowers,and Sr FT1 was only expressed in flowers and flower buds.