Morphological and Molecular Diversity of Barley (Hordeum vulgare L.) Genotypes and Assessment of Genetic Improvement in Ethiopia

Abstract

The effect of climate change together with the expected future demand represents a huge challenge for barley improvement in Ethiopia. Ethiopian barley germplasm is a potential source of useful traits to alleviate the production challenges of barley farming and to enhance yield productivity in both favorable and marginal environments. Performing morphological and molecular evaluation of barley genetic resources can provide an opportunity to develop improved cultivars that help to support production challenges and enhance its productivity. The overall objectives of the current study were to assess the morphological and molecular (SNP markers) diversity of barley genotypes and assess the genetic improvement of released food barley varieties in Ethiopia. Seventeen qualitative and twenty three quantitative traits of 125 barley genotypes were addressed using an alpha lattice design with two replications at Kulumsa Agricultural Research Center. The Shannon-Weaver diversity (H′) index was used to estimate qualitative traits of diversity. Principal component and cluster analyses were also applied to assess the qualitative and quantitative traits of diversity. For the molecular diversity study, genotyping using 10K single nucleotide polymorphism (SNP) marker was used to assess genetic diversity and population structure. Analysis of molecular variance (AMOVA) was carried out to address the total genetic variation that occurred within accessions and among populations. Fifteen qualitative traits of barley accessions originating from various regions and altitude ranges revealed high morphological variations. However, two traits namely stem branching and lemma awns were monomorphic. The highest (0.94) overall mean of H′ was obtained for glumes color, kernel row and kernel shape. The estimated H′ ranged from 0.41 to 0.99 across regions, and 0.52 to 0.99 across altitude ranges with an overall mean of 0.76. Heat map analysis based on qualitative traits of barley has grouped the genotypes into three distinct clusters. Estimates of variance (ANOVA) in the quantitative traits showed a significant variability that the majority of the measured traits had a wide range of variances. The heritability ranged from 16% for the number of tillers per plant to 94% for days to heading and flowering. The average gene diversity was 0.253, polymorphism information content (PIC) of 0.216, and minor allelic frequency (MAF) of 0.118 which revealed a high genetic variation in barley genotypes. The genetic differentiation also showed the existence of variations, ranging from 0.019 to 0.117, indicating moderate genetic differentiation between barley populations. The heat map, principal components and population structure analysis further confirmed the presence of four distinct clusters. Thus, this finding confirmed that the Ethiopian barley genotypes showed substantial genetic variations across the regions and altitude ranges. In the genetic improvement study, the yield of barley over the breeding periods showed consistent improvement. Based on regression analysis, grain yield has increased linearly at the rate of 0.021 tons ha-1 yr -1 . Over the past years, barley yield has significantly increased as a result of grain yield improvement. This improvement comes through consequent rounds of breeding involving the introduction of exotic and local collections in the barley breeding programs in Ethiopia. We recommend carefully considering this material as a source of genetic material for direct selection, the crossing of targeted traits to enhance productivity, tolerance to abiotic and abiotic stresses, and the quality of barley products using conventional programs and modern tools.