Construction Of Tagetes Erecta Primary Core Collection Based On Phenotypic Traits And SSR Marker Diversity Evaluation

Tagetes erecta L.,also known as Marigold,is an annual herb with bright,fragrant flowers that are not only ornamental but also medicinal.In addition,the extracts of marigold can be widely used in the dietary,beauty,health and medicine,feed additives and other industries,making it an important economic flower.At present,the germplasm resources of Marigold in China have not been well conserved,developed and utilised.Phenotypic and SSR molecular marker genetic diversity analysis of Marigold can not only provide a theoretical basis for the construction of primary core germplasm of Marigold,but also create the necessary conditions for the conservation and breeding of new varieties of Marigold.Therefore,in this study,101 Tagetes erecta germplasm mainly popularly applied in China’s market were used as materials to determine and compare 10 phenotypic traits in the field,analyse the genetic diversity and correlation between each index,analyse the genetic diversity of Marigold germplasm by combining with Tagetes erecta SSR molecular markers developed from previous transcriptome sequencing data,and finally construct the primary core germplasm of current Tagetes erecta resources,the main results of the study are as follows:(1)According to the 10 phenotypic traits such as plant height,crown width and flower diameter,the coefficient of variation of phenotypic traits of Tagetes erecta was large,ranging from 7.08 % to 57.90 %,indicating that there were significant differences in genetic diversity among different varieties.The variation coefficient of a* value of red and green indicators was the highest(57.90 %),and the diversity was the most significant.However,the coefficient of variation of CIRG value was the smallest(7.08 %),and there was little overall difference among varieties.The results of correlation analysis showed that there was a strong correlation among the 10 phenotypic traits,with 16 pairs of phenotypes showing extremely significant level and 4 pairs of phenotypes showing significant level.The correlation coefficient between a* value and lutein content was the highest and the correlation was the closest.Based on the data of phenotypic traits,101 marigold materials were clustered into two categories,the first category included 51 marigold germplasm,and the second category included 50 marigold germplasm,but the main phenotypic characteristics of the two types of germplasm were basically opposite.(2)The candidate polymorphic SSR markers were mined by reassembly joint analysis of the two transcriptome data in the early stage.The results showed that the sequence assembly was complete and the SSR loci were densely distributed.Then,the genetic diversity of 101 marigold germplasm resources was further analyzed by using the obtained conservative marker sites of the two.The results showed that 23 pairs of SSR markers finally detected 75 Na values,including 8 loci with high polymorphic information content,13 loci with medium polymorphic information content and 2 loci with the lowest polymorphic information content.Except for Ta CP049 and Ta CP027,the other 21 SSR loci were rich in polymorphism and high in genetic diversity.After that,all the tested materials were divided into two categories by population clustering and genetic structure analysis,including 28 and 73 marigold germplasm respectively.(3)Finally,based on the joint analysis of 10 phenotypic data and 23 molecular marker genotype data,a core collection of 45 marigold germplasm was constructed,which can represent the original germplasm.T-test of phenotypic data and molecular marker data showed that there was no significant difference between primary core germplasm and original germplasm.Finally,using principal component analysis,it has found that 45 primary core germplasm were evenly dispersed in the original germplasm on the analysis coordinate map,which was very representative.Considering the high similarity between the primary core germplasm and the original germplasm in morphology and molecular level,the primary core germplasm can represent the original germplasm for candidate research.