Root traits that enhance plant productivity under drought conditions are critical for improving crop yields in water-limited environments. Geneticists and breeders are well-positioned to develop plants with such traits, but a deeper understanding of root functional traits and their relationship to whole-plant strategies is needed. Key root traits associated with drought tolerance include small fine root diameters, long specific root length, and high root length density, especially in soil depths with available water. In late-season water deficits, small xylem diameters in seminal roots help conserve soil water for crop maturation, improving yields. Deep root growth and large xylem diameters in deep roots can enhance water acquisition when water is available at depth. Xylem pit anatomy that reduces "leakiness" and cavitation potential may improve productivity without negatively affecting yields under adequate water conditions. Rapid root regrowth after rewetting can also enhance productivity under episodic drought. Root traits are influenced by genetic factors, and breeding programs can target these traits to improve drought tolerance. However, the complexity of root systems, including differences between fine and coarse roots, requires careful consideration when screening for relevant traits. Early-stage root trait screening can predict mature traits, but case-by-case verification is necessary to ensure they are linked to increased productivity under drought. Examples from lesquerella and rice illustrate approaches to root trait phenotyping and current understanding of root trait genetics for breeding. Root systems in both woody and herbaceous plants consist of multiple root organs, with coarse roots providing structural support and fine roots involved in resource foraging. Root system size and allometry are important traits, with shifts in root-to-shoot ratios helping plants adapt to water shortages. Functional equilibrium theory suggests plants allocate resources to optimize growth, while optimal partitioning theory emphasizes whole-plant growth optimization. Root traits such as diameter, tissue density, specific root length, and specific surface area are associated with increased productivity under drought. These traits influence root length, surface area, and water uptake capacity. Xylem diameter affects root hydraulic conductivity and can influence plant productivity under drought. Large xylem vessels may increase hydraulic conductivity but also increase the risk of cavitation. Root traits such as xylem diameter, root hair production, and aquaporin expression can enhance water uptake and drought tolerance. Root growth and distribution under drought are influenced by environmental conditions and plant genotype, with deep roots being particularly important for water acquisition in dry environments. Root traits that allow for rapid regrowth after rewetting can enhance productivity under episodic drought. Root traits are often controlled by multiple genes, with interactions and environmental effects influencing their expression. Quantitative trait loci (QTL) associated with root traits under drought have been identified in various crops, including rice, wheat, and maize. These QTL can be used in marker-assisted selection (MAS) to improve drought tolerance. However, validation under field conditions is necessary before MAS can be effectively applied. Genetic diversity in root traits is important forRoot traits that enhance plant productivity under drought conditions are critical for improving crop yields in water-limited environments. Geneticists and breeders are well-positioned to develop plants with such traits, but a deeper understanding of root functional traits and their relationship to whole-plant strategies is needed. Key root traits associated with drought tolerance include small fine root diameters, long specific root length, and high root length density, especially in soil depths with available water. In late-season water deficits, small xylem diameters in seminal roots help conserve soil water for crop maturation, improving yields. Deep root growth and large xylem diameters in deep roots can enhance water acquisition when water is available at depth. Xylem pit anatomy that reduces "leakiness" and cavitation potential may improve productivity without negatively affecting yields under adequate water conditions. Rapid root regrowth after rewetting can also enhance productivity under episodic drought. Root traits are influenced by genetic factors, and breeding programs can target these traits to improve drought tolerance. However, the complexity of root systems, including differences between fine and coarse roots, requires careful consideration when screening for relevant traits. Early-stage root trait screening can predict mature traits, but case-by-case verification is necessary to ensure they are linked to increased productivity under drought. Examples from lesquerella and rice illustrate approaches to root trait phenotyping and current understanding of root trait genetics for breeding. Root systems in both woody and herbaceous plants consist of multiple root organs, with coarse roots providing structural support and fine roots involved in resource foraging. Root system size and allometry are important traits, with shifts in root-to-shoot ratios helping plants adapt to water shortages. Functional equilibrium theory suggests plants allocate resources to optimize growth, while optimal partitioning theory emphasizes whole-plant growth optimization. Root traits such as diameter, tissue density, specific root length, and specific surface area are associated with increased productivity under drought. These traits influence root length, surface area, and water uptake capacity. Xylem diameter affects root hydraulic conductivity and can influence plant productivity under drought. Large xylem vessels may increase hydraulic conductivity but also increase the risk of cavitation. Root traits such as xylem diameter, root hair production, and aquaporin expression can enhance water uptake and drought tolerance. Root growth and distribution under drought are influenced by environmental conditions and plant genotype, with deep roots being particularly important for water acquisition in dry environments. Root traits that allow for rapid regrowth after rewetting can enhance productivity under episodic drought. Root traits are often controlled by multiple genes, with interactions and environmental effects influencing their expression. Quantitative trait loci (QTL) associated with root traits under drought have been identified in various crops, including rice, wheat, and maize. These QTL can be used in marker-assisted selection (MAS) to improve drought tolerance. However, validation under field conditions is necessary before MAS can be effectively applied. Genetic diversity in root traits is important for