Phenotyping and Validation of Root Morphological Traits in Barley (Hordeum vulgare L.)

Barley (Hordeum vulgare L.) is an important cereal crop, but its sustainable production is significantly hampered due to the presence of various edaphic stresses. Understanding the variability in root morphological traits among diverse barley genotypes is critical for selecting those with suitable root traits for breeding new cultivars better adapted to stress environments. Root morphological traits in an early growth stage (30 days after transplanting) in a panel of 189 barley genotypes (mostly advanced breeding lines) were assessed using a semi-hydroponic phenotyping platform followed by a validation experiment of eight genotypes with contrasting root systems in two soils. The phenotyping experiment showed large variation (coefficient of variation values ≥ 0.25) in 16 of 26 measured root and shoot traits. A strong correlation among most of the selected traits was identified. Principal component analysis indicated four principal components (eigenvalues >1) captured 79.5% of the total variation. Root traits, including total root length, root length at various depths, root diameter and root length ratio (top 20 cm vs. lower section), could be considered in the barley breeding programs. Consistent ranking of the selected eight genotypes based on root biomass and root length in both the semi-hydroponic system and the columns with two different soils confirmed root trait performance in different growth environments as well as the reliability of the phenotyping method. This study identified phenotypic variability in root morphological traits in barley genotypes in the early growth stage. The genotypic variability in root traits represents a basis for mapping quantitative trait loci (QTLs) and molecular markers, particularly focused on breeding lines with optimal root properties for the efficient acquisition of soil resources and adaptation to drought and other abiotic stresses.