Abstract
BackgroundGrain protein content (GPC) is an important quality determinant for barley used as malt, feed as well as food. It is controlled by a complex genetic system. GPC differs greatly among barley genotypes and is also variable across different environments. It is imperative to understand the genetic control of barley GPC and identify the genotypes with less variation under the different environments.ResultsIn this study, 59 cultivated and 99 Tibetan wild barley genotypes were used for a genome-wide association study (GWAS) and a multi-platform candidate gene-based association analysis, in order to identify the molecular markers associated with GPC. Tibetan wild barley had higher GPC than cultivated barley. The significant correlation between GPC and diastatic power (DP), and malt extract confirmed the importance of GPC in determining malt quality. Diversity arrays technology (DArT) markers associated with barley GPC were detected by GWAS. In addition, GWAS revealed two HvNAM genes as the candidate genes controlling GPC. No association was detected between HvNAM1 polymorphism and GPC, while a single nucleotide polymorphism (SNP) (798, P < 0.01), located within the second intron of HvNAM2, was associated with GPC. There was a significant correlation between haplotypes of HvNAM1, HvNAM2 and GPC in barley.ConclusionsThe GWAS and candidate gene based-association study may be effectively used to determine the genetic variation of GPC in barley. The DArT markers and the polymorphism of HvNAM genes identified in this study are useful in developing high quality barley cultivars in the future. HvNAM genes could play a role in controlling barley GPC.
Highlights
Grain protein content (GPC) is an important quality determinant for barley used as malt, feed as well as food
TASSEL 2.01 was used to calculate linkage disequilibrium (LD) based on the parameter r2, which is a measurement of the correlation between a pair of variables [23]
The variation of protein content and Kolbach index The GPC in 59 cultivated and 99 Tibetan wild barley accessions ranged from 8.02% to 13.50% with a mean of 10.56% in 2008 and varied from 8.28% to 14.45% with a mean of 10.87% in 2009 (Figure 1)
Summary
Grain protein content (GPC) is an important quality determinant for barley used as malt, feed as well as food. It is controlled by a complex genetic system. GPC is closely associated with feed and malt quality. Barley GPC is under polygenic control, with many quantitative trait loci (QTLs) having been mapped on all seven chromosomes, mainly on 2H, 4H, 5H and 6H [3,4]. All these loci had been determined by QTL mapping.
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