| Sesame(Sesamum indicum L)is one of the ancient oil crops in the world.It is distributed all over the world and has a long planting history in China.Sesame is not only an important oil crop,but also a traditional high-quality food material.It also has important application value in medicine and chemical industry.Jiangxi Province is one of the four major sesame producing areas in China.It is planted in all cities in the province.The folk contains rich local germplasm,which provides important basic materials for the research of sesame genetics and breeding.However,due to the change of planting structure and the continuous popularization and utilization of bred varieties,local sesame germplasm are facing the risk of rapid loss in Jiangxi Province.In the preliminary work,our research group collected and preserved more than 700 sesame germplasm from counties and cities in Jiangxi Province,but the research on the evaluation,preservation and utilization of genetic diversity of sesame germplasm in Jiangxi Province is still blank.In the research of crop germplasm resources,the so-called "Core Germplasm Bank" has been established based on its phenotypic genetic diversity and / or genotype genetic diversity.The purpose is to represent the genetic diversity of crop germplasm to the greatest extent with the least number of germplasm,which is conducive to the efficient preservation and effective utilization of crop resources.Based on the data of 25 phenotypic traits,the genetic diversity of 736 sesame local germplasm was analyzed,and the core germplasm containing 110 sesame local germplasm in Jiangxi Province was constructed;Then the genetic diversity of the target core collection was further verified and analyzed from the phenotypic traits and SSR molecular marker data.The main results are as follows:1.Genetic diversity analysis of phenotypic traits of sesame land germplasm in JiangxiGenetic diversity analysis,correlation and principal component analysis were conducted on 25 phenotypic traits of 736 sesame local germplasm in Jiangxi Province.The results showed that the GDI of phenotypic traits ranged from 0.5129 to 2.0833,and the GDI of quantitative traits(1.7140-2.0833)was higher than that of quality traits(0.5129-1.2028).The coefficient of variation of 11 quantitative characters(except growth period)was greater than 10%.It can be seen that 736 sesame local germplasm have large phenotypic variation and rich genetic diversity.The results of comprehensive correlation analysis and principal component analysis showed that growth period,plant height,infertile top length,main stem capsule,the number of main stem capsules,mean capsule length and 1000-seed weight were positively correlated with yield per plant,and the contribution rate was the highest.Therefore,when breeding high-yield germplasm,we should select the yield factors with more main stem capsules,more number of main stem capsules,longer mean capsule length,heavier 1000-seed weight and larger yield per plant,and avoid the capsule traits with smaller capsule width,thinner capsule thickness and less seeds per capsule.2.Construction and sampling verification of sesame core germplasm in Jiangxi ProvinceIn this study,we use 736 local sesame germplasms as materials.It is clear that the primary core collection constructed by "multiple clustering priority sampling method + 15%sampling proportion + variable average method + Euclidean distance" can well represent the diversity of the original Germplasm Population,and the mean difference percentage,variance difference percentage,range coincidence rate and coefficient of variation percentage are 0,44%,100% and 110.21% respectively.On this basis,we test and evaluate the representativeness of primary core germplasm.Then 110 core germplasm were obtained.The genetic diversity index,coefficient of variation,correlation,principal component and cluster analysis were performed on 25 phenotypic traits of 110 sesame core germplasm.The results showed that the genetic diversity index of 25 phenotypic traits was in the range of0.5573-2.0687,and the variation coefficient was in the range of 4.83%-48.16%,which was basically close to that of the original collection population.The variation coefficients of 7traits of 12 quantitative traits were more than 20%.It can be seen that the phenotypic characteristics in 736 sesame germplasms were basically retained in 110 core collections.In addition,110 core collections were divided into four groups after clustering.The mean value of 25 characters in the core collection had no significant difference from the original collection,while the variance had significant or extremely significant difference from the original collection,which could represent the preservation and utilization of the original sesame resources.3.Genetic diversity analysis of genotype of sesame core germplasm in Jiangxi Province106 DNA bands were amplified from 110 sesame core germplasm with 25 SSR primer pairs,resulting polymorphic ratio of 100%,and the polymorphic bands amplified by each primer pair averaged 4.36.The variation range of primer polymorphism information content(PIC)value was 0.0476-0.3606,with an average of 0.2609,indicating that the selected primers provided less genetic information.The cluster analysis results calculated by Nei’s1973 genetic distance showed that the variation range of similarity coefficient among 110 core germplasm was 0.4528-0.9717,with an average of 0.6900,and the genetic distance was0.0283-0.5472,with an average of 0.3100.Given all the core germplasm be divided into three regions by different geographical directions,the overall genetic similarity is as follows:Northern Jiangxi(GS=0.7036)> Southern Jiangxi(GS=0.6940)> Central Jiangxi(GS=0.6858).The genetic diversity of sesame germplasm in central Jiangxi was more abundant than that in northern and southern regions,which may be associated with the frequent circulation of germplasm in central Jiangxi to both northern and southern locations.According to the seed color,it was divided into three types: white sesame,black sesame and other seed color sesame.From the comparison of genetic similarity coefficient and genetic distance,it is concluded that the genetic diversity of other seed color sesame germplasm is abundant,followed by white sesame germplasm,and the genetic diversity of black sesame germplasm was relatively poor in the three seed color types. |
