Assessment Of The Diversity Of The Genebank-preserved Chinese Barley Landraces By Genotyping-by-Sequencing

Genebanks reservation of crop species is a valuable resource for both academic studies and breeding practices.The National Crop Genebank of China(NCGC)preserved one of the largest barley collections(>23,000 accessions),including over 9900 Chinese barley landraces.However,the genetic diversity remained poorly illustrated,thus restricting the efficient use of this resource in academic and applied studies.Here,we deployed the genotyping-by-sequencing(GBS)and phenotping analysis,to investigate the diversity of 497 Chinese barley accessions,which account for ca.5% of NCGC-preserved Chinese barley landraces.The mjor results are listed as follows:1.By sequencing of 497 landraces,a total of 553 Gb nucleotide sequencs were generated,with 0.3 to 3 Gb data for single accession.After filtrating of those low quality reads,97% of the high-quality reads in each accession were mapped to the barley reference genome.By calling for polymorphism,over 2.5 million of SNPs/Indels were identified.With filtration by missing data<50% and minor allele frequency(MAF)>0.01,10,986 markers including SNPs and Indels have been identified among the 497 accessions.2.Taking advantage of the identified 10,986 markers,the heterozygosity of each accession was evaluated.Over 97% of the accessions showed heterozygosity within the range of 0.04 to 0.27,with an average level of 0.13.Higher level of heterozygosity has been found in landraces from Tibet than those from other regions.No completely identical accessions was observed within the 497 chinese barley landraces by pair-wised comparison,the pair-wised identity ranged from 57% to 91%,with a mean of 77%.Thirty-two accessions(6%)showed the identity over 90% with some others.3.PCA,STRUCTURE and phylogenetic analysis revealed there were three subpopulations within the Chinese barley landraces.However,there was no obvious correlation of the subpopulations with any of known passport features,for example geographical origin or growth habit.4.The overall nucleotide diversity(?)within each subpopulation was 0.093,0.157 and 0.129,respectively.Mealwhile,the gengtic differentiation(Fst)was found larger between G2 and the other two subpopulations.5.Abundant diversity was observed on spike and grain characters within these Chinese barley landraces.Thus,the rich genetic diversity,combined with a considerable level of heterozygosity,of the NCGC-preserved Chinese barley landraces,provided an important guidance in management and utilization of these resources.