Genetic Diversity Of Seven Elymus Breviaristatus Natural Populations From The Northwestern Sichuan Plateau

Elymus L. is the largest and most widely distributed genus in the tribe Triticeae, with some 150 species distributed in most temperate regions of the world. In recent years, numerous studies of population genetics have been undertaken in some Elymus species to deliberate the genetic variation. So far there is little study has been reported on the genetic diversity and differentiation in populations of Elymus breviaristatus. However, E. breviaristatus has been listed as the second category of key protected wild plants in China and it become less and less. Thus, we must set up a wide-ranging conservation plans to protect the genetic diversity of this endangered species. This study reveal phenotypic variation of E. breviaristatus populations, and genetic diversity and population structure of E. breviaristatus populations were assessed by SRAP (sequence-related amplified polymorphism) and EST-SSR (expressed sequence tags-simple sequence repeats). In order to provide the theory basis for formulate reasonable measures to protect the genetic diversity of E. breviaristatus. Further, it can providing the theory basis for collect, evaluate and conserve the Elymus species.1.32 phenotypic traits for 84 individuals in 7 populations from the northwestern Sichuan Plateau were investigated by adopting the methods of nested analysis of variance, coefficient of variation, principal coordinate (PCO) analysis, correlation analysis and cluster analysis. The results are as follows:(1) There is significant difference in morphologic characteristics within or between the populations of E. breviaristatus, between the populations, the F value of LW (flag leaf width) (25.9032) is largest, within the populations, the F value of LMW (width of lemma) (3.0529) is largest; (2) The phenotypic differentiation coefficient is 58.34% within populations, which is higher than that between the populations (41.66%). The result demonstrates that the variation within populations is mainly due to the phenotypic variation of E. breviaristatus; (3) The analysis for the correlations between the phenotypic traits of E. breviaristatus and geographical and ecological factors showed that:except the LGL (length of lower glume) and NVLM (number of veins of lemma), there is no significant correlations between the remain phenotypic traits of E. breviaristatus and geographical and ecological factors; (4) The result of UPGMA cluster analysis for the E. breviaristatus populations by calculating euclidean distance among the populations showed that the E. breviaristatus populations could be clustered into four groups; (5) Euclidean distance showed no association with geographic distance between the population sites of origin based on the Mantel test (r= 0.334, P= 0.083).2. Genetic diversity of seven E. breviaristatus populations were assessed by nineteen SRAP primer pairs. The results are as follows:(1) Different primer pairs amplified variable number of bands, from 20 to 36, with an average of 24 fragments per primer combination. The mean polymorphism information content (PIC) is 0.2983; (2) At the population level, the proportion of polymorphic bands (PPB), the genetic diversity (He), Shannon’s information index, Bayesian heterozygosity (HB) and the expected heterozygosity (Hj, analogous to He) by AFLPsurv were 0.5288,0.1859,0.2406,0.2224 and 0.2086, respectively; At the species level, the PPB, He, I, HB and Hj values equaled 0.9237,0.3314, 0.4490,0.3608 and 0.3812, respectively; (3) The genetic differentiation among populations as estimated by partitioning of the total gene diversity, there are 43.93%(GST=0.4393 by Nei’s gene diversity),46.41%(Shannon’s information index),34.78%(FST=0.3478 by Lynch & Milligan),38.36%(GST-B= 0.3836 by Bayesian method),49.20%(OSt= 0.4920 by AMOVA analysis) of the total variation results from differentiation among populations of E. breviaristatus. (4) The value of genetic distance (D) between the populations varied from 0.1105 to 0.292 with an average of 0.225. Genetic distance showed no association with geographic distance between the population sites of origin based on the Mantel test (r= 0.2197, P= 0.2534).3. Genetic diversity of seven E. breviaristatus populations were assessed by seventeen EST-SSR primer pairs. The results are as follows:(1) There were 166 fragments out of 199 were polymorphic bands. Different primer pairs amplified variable number of bands, from 3 to 16, with an average of 12 fragments per primer combination. The mean PPB was 83.42%, the mean PIC was 0.6589; (2) At the population level, Shannon’s information index (Ip) was 0.1152. Among the 7 populations investigated, Pop 1 exhibited the highest genetic variability, whereas the Pop 6 had the lowest genetic variation. At the species level, the Shannon’s information index (Is) was 0.2506; (3) The genetic differentiation among populations as estimated by partitioning of the total gene diversity, there was 54.03%(Gst =0.5403 by Shannon’s information index),47.75%(OSt=0.4775 by AMOVA analysis); (4) Genetic distance (ΦPT) among the populations varied from 0.279 to 0.659 with an average of 0.358, which showed no association with geographic distance among the population sites based on the Mantel test (r= 0.252, P= 0.203).