Unveiling early-stage responses of sensitive traits to water stress in tropical maize: a characterization study of a public panel

One of the major goals of modern agriculture is to achieve increased crop yield using less water. Despite significant advancements in genomics, an efficient phenotypic characterization remains indispensable for the success of modern breeding programs aiming to expedite genetic gains through early-stage selection deployment. Thus, this study aimed to identify which traits are most important to discriminate the maize genotypes to support early selection under contrasting water availability conditions. For this, we used a public diversity panel of 360 tropical maize inbred lines, involving two conditions, well-watered (WW) and water-stress (WS) across eight trials. Evaluations were carried out in the phenological stage V6 for shoot and root traits. There was a significant variation in the panel performance, mainly for root traits under WS conditions, composing six clusters. Notably, clustering patterns based on principal components were similar under WW and WS conditions. A strong correlation was found among roots length, surface area, and volume,  allowing the exclusion of more error-prone traits. Redundancy analysis (RDA) highlighted plant height, stalk diameter, and lateral roots length as the most sensitive traits to WS, suggesting their utility in early selection for water-use efficiency in maize breeding programs.