Investigating the Role and Response of Root Groups of <scp> <i>Hordeum vulgare</i> </scp> subsp. <i>spontaneum</i> Germplasm to Drought Stress

<i>Hordeum vulgare</i> subsp. <i>spontaneum</i>, the wild progenitor of cultivated barley, shares the same chromosome number with domesticated forms and exhibits no significant biological barriers to interspecies crossing. Roots are essential for water uptake, nutrient acquisition, and structural support, making them key determinants of plant performance under drought stress. The present study aimed to investigate the diversity in root group responses to water deficit across 114 genotypes of wild barley. The experiment was conducted in an Augmented Block Design with two soil moisture regimes: normal conditions at 90%-95% field capacity (FC) and water stress at 50%-55% FC. Genotypes were classified into nine groups based on mean root length and root tissue density, calculated within a 95% confidence interval, under both moisture regimes. Discriminant analysis revealed that the three main discriminant functions explained 95.3% and 94.2% of the total variance under normal and water stress conditions, respectively. Analysis of variance revealed that the genotype × stress interaction effect was not significant for root diameter under drought stress. However, seedling length, root dry weight, root surface area density, and chlorophyll content were significant at <i>p</i> < 0.05, while all other measured traits were significant at <i>p</i> < 0.01. Mean root trait analysis demonstrated considerable variation among genotypes, indicating broad genetic diversity in root and shoot characteristics. Cluster analysis classified the root groups into three clusters under both water stress and normal conditions. These findings provide insights into the adaptive potential of wild barley roots under drought, supporting their use in breeding for stress tolerance.