Fine-mapping and characterisation of genes on barley(Hordeum vulgare)chromosome 2H for salinity stress tolerance during germination

Salinity causes a detrimental impact on plant growth,particularly when the stress occurs during germination and early development stages.Barley is one of the most salt-tolerant crops;previously we mapped two quantitative trait loci(QTL)for salinity tolerance during germination on the short arm of chromosome 2 H using a CM72/Gairdner doubled haploid(DH)population.Here,we narrowed down the major QTL to a region of 0.341 or 0.439 Mb containing 9 or 24 candidate genes belonging to 6 or 20 functional gene families according to barley reference genomes v1 and v3 respectively,using two DH populations of CM72/Gairdner and Skiff/CM72,F_(2)and F;generations of CM72/Gairdner/;Spartacus CL,Two Receptorlike kinase 4(RLPK4)v1 or Receptor-like kinase(RLK)v3 could be the candidates for enhanced germination under salinity stress because of their upregulated expression in salt-tolerant variety CM72.Besides,several insertion/deletion polymorphisms were identified within the 3 rd exon of the genes between CM72 and Gairdner.The sequence variations resulted in shifted functional protein domains,which may be associated with differences in salinity tolerance.Two molecular markers were designed for selecting the locus with receptor-like protein kinase 4,and one was inside HORVU2 Hr1 G111760.1 or HORVU.MOREX.r3.2 HG0202810.1.The diagnostic markers will allow for pyramiding of 2 H locus in barley varieties and facilitate genetic improvement for saline soils.Further,validation of the genes to elucidate the mechanisms involved in enhancing salinity tolerance at germination and designing RLPK4 specific markers is proposed.For this publication,all the analysis was based on barley reference genome of2017(v1),and it was used throughout for consistence.However,the positions of the markers and genes identified were updated according to new genome(v3)for reference.

Salinity tolerance in barley during germination——homologs and potential genes

Salinity affects more than 6%of the world’s total land area,causing massive losses in crop yield.Salinity inhibits plant growth and development through osmotic and ionic stresses;however,some plants exhibit adaptations through osmotic regulation,exclusion,and translocation of accumulated Na+or Cl-.Currently,there are no practical,economically viable methods for managing salinity,so the best practice is to grow crops with improved tolerance.Germination is the stage in a plant’s life cycle most adversely affected by salinity.Barley,the fourth most important cereal crop in the world,has outstanding salinity tolerance,relative to other cereal crops.Here,we review the genetics of salinity tolerance in barley during germination by summarizing reported quantitative trait loci(QTLs)and functional genes.The homologs of candidate genes for salinity tolerance in Arabidopsis,soybean,maize,wheat,and rice have been blasted and mapped on the barley reference genome.The genetic diversity of three reported functional gene families for salt tolerance during barley germination,namely dehydration-responsive element-binding(DREB)protein,somatic embryogenesis receptor-like kinase and aquaporin genes,is discussed.While all three gene families show great diversity in most plant species,the DREB gene family is more diverse in barley than in wheat and rice.Further to this review,a convenient method for screening for salinity tolerance at germination is needed,and the mechanisms of action of the genes involved in salt tolerance need to be identified,validated,and transferred to commercial cultivars for field production in saline soil.