This study was aimed to identify genotypic diferences in shoot growth rate and root architecture traits in response to waterdefcit stress at early growth stages of wheat seedling, and to quantify relationships between genotypic variation in shoot physiological traits and root system architecture with a drought tolerance at several development stages. Eight bread wheat cultivars, namely Bam, Mahooti, Roshan, Tabbasi, Atrak, Falat, Shiraz and Qods, were grown in polyvinyl chloride tubes flled with soil in the greenhouse under well-watered and water-defcit stress conditions. Water stress elicited genotypic variation in root traits and shoot growth across cultivars. Drought stress decreased root architecture traits, with greater efects in drought-sensitive cultivars compared with those that were drought-tolerant. Branch root length was less infuenced compared with seminal root length. We showed that cultivars Roshan and Bam were most tolerant to drought due to their shorter distance between the frst branch root and the root tip, higher branch root length, longer seminal roots and higher stomatal conductance compared to the other cultivars. Positive relationship between root growth and shoot physiological responses was quantifed upon drought stress, highlighting the role of leveraging more efcient root systems as a strategy to enhance resource uptake under water-defcit conditions. Thus, root growth responses can be used as a drought tolerance selection criterion at the seedling stage of employed genotypes.
