Harnessing the variability in root architecture and VsNGR gene expression for drought adaptation in common vetch

Root system architecture (RSA) is a key determinant of drought adaptation, particularly in rainfed crops such as common vetch (Vicia sativa L.). This study evaluated RSA traits together with shoot and root biomass in seedlings of 27 vetch genotypes from six countries under control conditions and water stress induced by 12.5% polyethylene glycol (PEG) using the rhizoslide system. Substantial genetic variation was detected for all traits, with generally high coefficients of variation and broad sense heritability. Significant genotype × environment interactions were observed for all traits except the maximum angle of adventitious or lateral root separation at 5cm depth. Based on their responses to water stress, genotypes were classified into four groups (A-D). Group C was the most sensitivity, whereas Group D, represented by genotype V25, showed the highest resilience and represents a promising source of drought-tolerance traits for breeding. The study also identified, isolated, and sequenced VsNGR, a candidate gene involved in controlling root growth angle and rooting depth. Quantitative PCR analysis of three representative genotypes revealed highly significant differences in VsNGR expression among taproot, adventitious roots, and lateral roots. A strong negative correlation (r = -0.98) was observed between root growth angle and VsNGR expression. These findings support the hypothesis that VsNGR is associated with root architecture in common vetch and represents a promising target for breeding varieties with deeper root systems and improved adaptation to drought and climate change.