Rainfed sugarcane under water limitation: agronomic challenges and breeding perspectives

Sugarcane is a highly productive crop due to its high photosynthetic efficiency. Such productivity is associated with high water requirements, making sugarcane sensitive to water limitation. With a predominance of rainfed cultivation worldwide, sugarcane is increasingly exposed to drought under changing climate conditions. We highlight how sugarcane's response to water limitation is driven by plant developmental stage, canopy architecture and dynamics, root system functioning, and how these factors influence the identification of traits related to drought tolerance. We synthesize current knowledge on physiological, anatomical, and architectural mechanisms involved in drought tolerance, with particular emphasis on the formative growth phase, when water deficits have long-lasting effects on canopy development and yield. Water-use-related traits, including stomatal regulation and transpiration efficiency, are dependent on the plant developmental stages and often confounded by structural and microclimatic effects within the sugarcane canopy. Architectural and physiological traits can be leveraged through high-throughput field phenotyping, digital tools, and crop models to support trait-based breeding under water-limited conditions. However, the complexity of measuring these traits can limit their deployment in breeding programs. We conclude by identifying research priorities to integrate phenotyping, modeling, management practices and breeding approaches for developing sugarcane cultivars and production systems resilient to increasing water scarcity.