Phenolic acid metabolites have important physiological functions, and many genetic loci affecting phenolic acid metabolism traits have been identified in several crops. Although barley is one of the important cereal crops, research on the genetic basis of phenolic acid synthesis in barley grains remains limited. Here, we analyze the 39 phenolic acid metabolites detected in mature grains of barley double haploid (DH) population and further identify 154 metabolite quantitative trait loci (mQTLs) related to 36 phenolic acids using four mapping methods. Subsequently, we identify 12 candidate genes that affect the content of phenolic acid metabolites, and overexpression of one candidate gene, HvCOMT-1, in barley reveals its involvement in the synthesis of phenolic acids. Moreover, we show that the transcription factor HvMYB-1 regulate the expression of HvCOMT-1. Functional analysis in Arabidopsis shows that HvCOMT-1 increases stem diameter and lignin deposition. Further analysis reveals that the expression level of HvCOMT-1 is closely related to the barley lodging-related traits. Overall, our findings enhance the understanding of the genetic basis for phenolic acid variations in mature barley grains and provide valuable reference for genetic improvement of barley nutritional quality.
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