Dissecting salt tolerance in the Zhenmai wheat series through phenotypic and miRNA analysis

Soil salinity poses severe constraints to wheat productivity. Nevertheless, genotypic variation in salt tolerance and the miRNA-mediated regulatory networks underlying this trait remain poorly understood. In the present study, we evaluated salt tolerance across 25 Zhenmai wheat genotypes and systematically characterized salt-responsive miRNAs from 4 genotypes exhibiting contrasting salt tolerance. Among those genotypes, Z10 and Z23005 exhibited markedly greater salt tolerance than the sensitive genotypes Z23 and Z26, as evidenced by greater shoot biomass and less shoot Na⁺ accumulation under salt stress. Small RNA sequencing revealed distinct miRNA expression profiles between salt-tolerant and salt-sensitive genotypes. Tolerant genotypes possessed a unique set of salt-responsive differentially expressed miRNAs, whose predicted target genes were significantly enriched in biological pathways associated with ion homeostasis, transcriptional regulation, and stress defence metabolism. Co-expression network analysis identified 12 novel hub miRNAs potentially involved in the regulation of wheat responses to salt stress. Further screening identified 7 candidate genotype-specific miRNAs that target critical salt-tolerance genes, including NHX transporters, MYB/bZIP/WRKY transcription factors, and stress-responsive protein kinases. This study delineates genotype-specific miRNA regulatory cascades governing wheat salt tolerance and identifies promising molecular candidates for genetic improvement of salt tolerance in cultivated wheat.