HvGST plays a key role in anthocyanin accumulation in colored barley.

Blue aleurone of barley is caused by the accumulation of delphinidin-based derivatives. Although these compounds are ideal nutrients for human health, they are undesirable contaminants in malt brewing. Therefore, the ability to add and remove this trait easily would facilitate breeding barley for different purposes. Here we identified a glutathione S-transferase gene (HvGST) that was responsible for the blue aleurone trait in Tibetan qingke barley by performing a genome-wide association study and RNA-sequencing analysis. Gene variation and expression analysis indicated that HvGST also participates in the transport and accumulation of anthocyanin in purple barley. Haplotype and the geographic distribution analyses of HvGST alleles revealed two independent natural variants responsible for the emergence of white aleurone: a 203-bp deletion causing premature termination of translation in qingke barley and two key single nucleotide polymorphisms in the promoter resulting in low transcription in Western barley. This study contributes to a better understanding of mechanisms of colored barley formation, and provides a comprehensive reference for marker-assisted barley breeding.

Natural variations of HvSRN1 modulate the spike rachis node number in barley.

Grain number, one of the major determinants of yield in Triticeae crops, is largely determined by spikelet number and spike rachis node number (SRN). Here, we identified three quantitative trait loci (QTLs) for SRN using 145 recombinant inbred lines derived from a barley R90/1815D cross. qSRN1, the major-effect QTL, was mapped to chromosome 2H and explained up to 38.77% of SRN variation. Map-based cloning revealed that qSRN1 encodes the RAWUL domain-containing protein HvSRN1. Further analysis revealed that two key SNPs in the HvSRN1 promoter region (∼2 kb upstream of the transcription start site) affect the transcript level of HvSRN1 and contribute to variation in SRN. Similar to its orthologous proteins OsLAX2 and ZmBA2, HvSRN1 showed protein-protein interactions with HvLAX1, suggesting that the LAX2-LAX1 model for spike morphology regulation may be conserved in Poaceae crops. CRISPR-Cas9-induced HvSRN1 mutants showed reduced SRN but increased grain size and weight, demonstrating a trade-off effect. Our results shed light on the role of HvSRN1 variation in regulating the balance between grain number and weight in barley.