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MicroRNAs are ~22 nucleotide long non-coding RNAs that regulate gene expression at posttranscriptional level. Genome-wide analysis was performed to identify polycistronic miRNAs from wheat. Total 89 polycistronic miRNAs were identified in bread wheat which were distributed on three component sub-genomes (A = 26, B = 33 and D = 30). Except some, most of the identified polycistronic miRNAs were also present in other cultivated and wild wheat species. Expression of 11 identified polycistronic miRNAs could be validated using previously assembled transcriptomes, RNA-seq/s-RNA seq data of cultivated and wild wheats and RT-PCR. Polycistronic miRNAs orthologs were also localized on rice and Brachypodium genomes. As a case study, we also analyzed molecular evolution of miR395 family polycistrons in wheat. Both tandem and segmental duplications contributed to expansion of miR395 family polycistrons. Our findings provide a comprehensive view on wheat polycitronic miRNAs that will enable their in-depth functional analysis in the future. • Polycitrsonic microRNA (miRNA) loci exist in wheat and these are broadly conserved across the ancestral wheat species. • Expression of 11 polycistronic miRNA loci were validated using previously assembled transcriptomes, deep small RNA sequencing (sRNA-seq) data sets and reverse transcription-polymerase chain reaction (RT-PCR). • miR395 family polycistrons were evolved by duplication and subsequent divergence of an ancestral basic polycitronic unit containing two genes. • Massive loss of nucleotide diversity at majority of the A sub-genome polycistronic miRNA loci during domestication. However, a few polycistronic loci were highly conserved across domesticated and wild wheat. [ABSTRACT FROM AUTHOR]

A genome-wide association study (GWAS) was conducted using six different multi-locus GWAS models and 35K SNP array to demarcate genomic regions underlying reproductive stage salinity tolerance. Marker-trait association analysis was performed for salt tolerance indices (STI) of 11 morpho-physiological traits, and the actual concentrations of Na+ and K+, and the Na+/K+ ratio in flag leaf. A total of 293 significantly associated quantitative trait nucleotides (QTNs) for 14 morpho-physiological traits were identified. Of these 293 QTNs, 12 major QTNs with R2 ≥ 10.0% were detected in three or more GWAS models. Novel major QTNs were identified for plant height, number of effective tillers, biomass, grain yield, thousand grain weight, Na+ and K+ content, and the Na+/K+ ratio in flag leaf. Moreover, 48 candidate genes were identified from the associated genomic regions. The QTNs identified in this study could potentially be targeted for improving salinity tolerance in wheat. • Fifty consistent genomic regions were demarcated for 13 morpho-physiological traits using six multi-locus GWAS models. • Four highly consistent QTNs/genomic regions, one each for flag leaf Na+ content (Q.Na-6AL), flag leaf K+ content (Q.K-1AS), above ground biomass (Q.STI-BM-1BL) and Na+/K+ Ratio (Q.NaK-1BS) were identified. • Wheat chromosome 5B harbored the maximum number of genomic regions for yield contributing traits. • The identified QTN regions contained some important stress responsive candidate genes encoding for cytochrome 450 (CYP) family protein, detoxification protein, auxin responsive protein, MYB family transcription factor and peptidylprolyl isomerase (PPI). • ISIS EM-BLASSO is the most efficient model for multi-trait mapping of reproductive stage salinity tolerance. [ABSTRACT FROM AUTHOR]