Abstract
In barley, six-rowed barley is advantageous over two-rowed barley for feed due to the larger number of seeds per spike and the higher seed protein content. The growth of six-rowed barley is potentially important for breeding in agriculturally oriented countries, such as Kazakhstan. Nevertheless, until recently, very little attention was given to six-rowed barley in breeding projects in Kazakhstan, one of the largest countries in the world. In this study, phenotyping and single nucleotide polymorphism (SNP) genotyping data were generated from 275 accessions originating from six different breeding organizations in the USA as well as 9 accessions from Kazakhstan in field trials at six breeding institutions. The USA six-rowed barley was tested in comparison to local accessions over three years (2009–2011) based on analyses of key agronomic traits. It was determined that the average yield in the USA accessions in comparison to local lines showed heavier yield in all six tested sites. Principal Coordinate Analysis based on 1618 polymorphic SNP markers separated Kazakh lines from six USA barley origin groups based on PC1 (77.9%), and Montana lines from the remaining five USA groups based on PC2 (15.1%). A genome-wide association study based on eighteen field trials allowed the identification of 47 stable marker-trait associations (MTA) for ten agronomic traits, including key yield related characters such as yield per square meter, thousand grain weight, number of kernels per spike, and productive tillers. The comparison of chromosomal positions of identified MTA with positions of known genes and quantitative trait loci suggests that 25 out of those 47 MTAs are presumably novel. The analysis of 42 SNPs associated with 47 MTAs in the Ensemble genome annotation system (http://ensemblgenomes.org) suggested that 40 SNPs were in genic positions of the genome, as their sequences successfully aligned with corresponding Gen ID.
Highlights
In barley, two-rowed (TR) and six-rowed (SR) germplasm groups can be separated based on the arrangement of triplets at rachis nodes [1]
The genotype (G) showed significant importance in genotype-environment interaction (GEI) as the origin of the accessions played an important role for three agronomic traits related to the spike architecture (NKS and thousand grain weight (TGW)), and contributed to the plant height (PH) (Table 2)
The results suggest that three MT lines are better adapted and advantageous in the northern region, which confirms a report from the study of TR barley [23]
Summary
Two-rowed (TR) and six-rowed (SR) germplasm groups can be separated based on the arrangement of triplets at rachis nodes [1]. The main objective in barley breeding is the development of new cultivars for feed, as the malting industry is largely undeveloped in this country. Countries with similar environments to Kazakhstan in terms of climate and latitude, such as the USA, are potential sources of germplasm for SR barley activities. This approach to the selection of foreign germplasm is interesting, as the USA barley-oriented research organizations have a long history for breeding SR barley [1, 7]. The USA barley cooperative agricultural program (CAP) has generated large barley resources, including germplasm [10, 11] that are available for the development of breeding projects around the World
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