Genome diversity and highland-adaptative variation in Tibet barley landrace population of China.

Barley landraces accumulated variation in adapting to extreme highland environments during long-term domestication in Tibet, but little is known about their population structure and genomic selection traces. In this study, tGBS (tunable genotyping by sequencing) sequencing, molecular marker and phenotypic analyses were conducted on 1,308 highland and 58 inland barley landraces in China. The accessions were divided into six sub-populations and clearly distinguished most six-rowed, naked barley accessions (Qingke in Tibet) from inland barley. Genome-wide differentiation was observed in all five sub-populations of Qingke and inland barley accessions. High genetic differentiation in the pericentric regions of chromosomes 2H and 3H contributed to formation of five types of Qingke. Ten haplotypes of the pericentric regions of 2H, 3H, 6H and 7H were further identified as associated with ecological diversification of these sub-populations. There was genetic exchange between eastern and western Qingke but they shared the same progenitor. The identification of 20 inland barley types indicated multiple origins of Qingke in Tibet. The distribution of the five types of Qingke corresponded to specific environments. Two predominant highland-adaptative variations were identified for low temperature tolerance and grain color. Our results provide new insights into the origin, genome differentiation, population structure and highland adaptation in highland barley which will benefit both germplasm enhancement and breeding of naked barley.

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.

Rare allele of HvLox-1 associated with lipoxygenase activity in barley (Hordeum vulgare L.).

KEY MESSAGE: Identification and allele-specific marker development of a functional SNP of HvLox - 1 which associated with barley lipoxygenase activity. Improving the stability of the flavor of beer is one of the main objectives in breeding barley for malting, and lipoxygenase-1 (LOX-1) is a key enzyme controlling this trait. In this study, a modified LOX activity assay was used for null LOX-1 mutant screening. Four barley landraces with no detected level of LOX-1 activity were screened from 1,083 barley germplasm accessions from China. The genomic sequence diversity of the HvLox-1 gene of the four null LOX-1 Chinese landraces was compared with that of a further 76 accessions. A total of 104 nucleotide polymorphisms were found, which contained 83 single-nucleotide polymorphisms (SNPs), 7 multiple-nucleotide polymorphisms, and 14 insertions and deletions. Most notably, we found a rare C/G mutation (SNP-61) in the second intron which led to null LOX-1 activity through an altered splicing acceptor site. In addition, an allele-specific polymerase chain reaction marker was developed for the genotyping of SNP-61, which could be used in breeding programs for barley to be used for malting. The objective was to improve beer quality.