Genome-wide Association Analysis Of Barley Grain Size

Grain size and 1000-grain weight of barley are not only important yield factors,but also important quality traits.In this study,600 wild and 400 cultivated barley materials with wide genetic representativeness were selected to compare the correlation and difference of grain length,grain width,grain thickness and 1000-grain weight between cultivated and wild barley,hulled barley and hulless barley,and the whole genome association analysis(GWAS)was carried out.The main results are as follows:1.There were significant differences in grain size among different genotypes.The average 1000-grain weight(39.7g)of cultivated barley was significantly higher than that of wild barley(35.9g).The 1000-grain weight(41.9g)of hulled barley was significantly higher than that of hulless barley(36.3g).The average grain length of wild barley(10.4 mm)was significantly higher than that of cultivated barley(8.9 mm).The average grain length(9.7mm)of hulled barley was significantly higher than that of hulless barley(7.6mm).The grain width of wild barley(3.0mm)was significantly smaller than that of cultivated barley(3.4mm).There was no significant difference in grain width between hulled barley and hulles barley,but there was significant difference between years.The grain thickness of cultivated barley(2.5 mm)was significantly higher than that of wild barley(1.9 mm),and there were significant differences among hulled,hulless and year.2.The correlation analysis of barley grain size indicators showed that grain width and grain thickness were significantly correlated with grain weight(0.6-0.8),and the correlation between grain width and grain weight was slightly higher than that of grain thickness;grain length in 2016 was negatively correlated with grain width and grain thickness,and grain length in 2017 was negatively correlated with grain thickness,indicating that these indicators had certain environmental effects.There was a significant correlation between grain width and grain thickness of barley(0.8-1.0).Principal Component Analysis(PCA)results showed that wild barley and cultivated barley could be distinguished in two-dimensional coordinates,and hulled barley and hulless barley could also be distinguished from each other.The sum of principal components 1 and 2 reached 91.2%,indicating that the grain shape and 1000-grain weight of barley might be controlled by the main genome.The screened genetic materials with specific grain size can also provide original materials or genes for barley breeding.3.47 QTL loci were located in wild barley and 50 QTL loci were located in cultivated barley,including 8 overlap loci between cultivated and wild barley.Location loci were associated with multiple trait genes(florescence,plant height,glucan,crisp spike axis,hormone,prism,starch synthesis,protein synthesis),indicating that barley grain size and 1000-grain weight were regulated by multiple genes and associated with multiple traits.Starch synthesis and protein synthesis genes have a great influence on grain size.There are obvious differences between cultivated and wild barley grain size QTL loci and starch synthesis and protein synthesis-related genes.In wild barley,grain length and grain thickness-related QTL89 is close to GBSS I gene,while in cultivated barley,grain width,grain thickness and 1000-grain weight-related QTL 10 is close to Starch synthase gene.E gene;No site close to protein synthesis related gene was located in wild barley,but the QTL38 close to protein synthesis related gene HvNAM1 was successfully located in cultivated barley.Both GBSS I gene and QTL loci near Starch synthase gene are related to grain thickness,which proves the importance of starch accumulation to grain thickness.In this study,the grain shape and 1000-grain weight of barley germplasms with wide genetic representation were compared and analyzed,and the difference and correlation of grain shape and 1000-grain weight between cultivated and wild barley were further revealed.By genome-wide association analysis.a large number of potential QTL loci related to grain shape and 1000-grain weight were obtained.Compared with the existing reports and annotation information of barley genome,some potential functional regions and candidate genes were obtained.which provided an important reference for subsequent barley grain size-related gene mining.