Studies On Genetic Diversity Of Psammochloa Villosa,a Peculiar Sandy Plant

Psammochloa villosa?Trin.Bor?is a perennial herb of Gramineae and Psammochloa Hitchc,which mainly depends on rhizomes to breed.It has strong drought,cold,alkali and wind and sand resistance.It is the key or unique herbaceous species distributed in extreme sandy environment.It not only has important ecological value,but also is an important dominant forage.It is also one of the most potential research objects of wild forage utilization and extreme environmental plant genetic resources.Therefore,based on the comprehensive field investigation,the genetic diversity and distribution pattern of Psammochloa villosa in China were studied by phenotypic morphology and DNA molecular marker technology in order to provide scientific basis for the protection and utilization of Psammochloa villosa germplasm resources.The main results are as follows:1.Through the study of phenotypic genetic diversity of Psammochloa villosa,it is found that there are abundant phenotypic genetic diversity of Psammochloa villosa,and the inter-group variation is greater than the intra-group variation.Among them,the variation coefficient of flag leaf length-width ratio is the largest,which was 32.44%.And the variation coefficient of plant-related traits is about 20%.The correlation coefficient of phenotypic traits is 0.002⁰.875,and the correlation between plant-related traits?such as plant height,inflorescence length,spikelet length,etc.?is extremely significant.The cumulative contribution rate of principal components is 73.447%,of which principal components 1 and 4 mainly reflect reproductive organ traits,and principal components 2 and 3 mainly reflect vegetative organ traits.The results of cluster analysis based on Euclidean distance showed that there was no correlation between the clustering results of phenotypic traits and the geographical distribution of the population,mainly related to plant height,flag leaf length,flag leaf width,inflorescence length,lemma length and other phenotypic traits.2.DNA molecular markers are used to analyze the genetic diversity of Psammochloa villosa.The results showed that the genetic diversity within the population is greater than that among the populations.The genetic differentiation between populations is significant and did not undergo rapid expansion.The total length of ITS fragments is 509 bp,with 135 mutation sites and 34 haplotypes were detected?H1-H34?.H2 and H3 are distributed in most populations,and H1,H4,H8,H17 and H29 are shared by a few populations.The rest haplotypes are unique to some populations and are randomly distributed in the population.The haplotype diversity?H_D?of Psammochloa villosa is 0.535,the nucleotide diversity???is 0.07798,the average nucleotide difference index?K?is 46.479.The genetic diversity index of different populations is different,and the trend of variation is consistent.The total genetic diversity and intra-population genetic diversity are relatively low?Ht=0.559,Hs=0.338?,the coefficient of gene differentiation among populations was relatively small(G_ST=0.396),and there was no obvious pedigree geographical structure(G_ST<N_ST,P>0.05).The genetic variation of Psammochloa villosa mainly exists in the population(F_ST=0.27445,P<0.01),and the gene flow between populations is limited?Nm=1.322?.Tajima's D=4.39669?P value is uncertain?,Fu and Li's D*=2.85635?P<0.05?,Fu and Li's F*=4.39449?P<0.05?,and the mismatch distribution shows a bimodal curve,which proves that Psammochloa villosa may experience selection effect.3.The total length of the chloroplast genome was 135,541 bp and the GC content was38.8%.The chloroplast genome showed a typical four-segment structure:large single-copy region?LSC?,small single-copy region?SSC?and two reverse repeat regions?IRs?with lengths of 80,272 bp,12,453 bp and 21,408 bp.The chloroplast genome contains 134 genes,including79 protein-coding genes,42 tRNA genes and 10 rRNA genes.Among these genes,12 genes contain one intron and 3 genes contain two introns.