Rice Responses to Water Limiting Conditions: Improving Stress Management by Exploiting Genetics and Physiological Processes

Water-limiting conditions can severely affect rice yield. Therefore, increasing plant tolerance to water stress is a priority for many rice breeding programs. However, improving rice tolerance to this abiotic stress comes with several complications related to the seeding practices, the adopted water management system and the growth stage where water stress occurs. For this reason, it is challenging to outline single ideotypes showing traits suitable for overcoming drought at different times during the life cycle of rice in diverse cropping ecosystems. The current knowledge of genomics and biochemicals can contribute to drawing rice ideotypes flexible towards diverse water availability conditions. Traits identified in accessions of the wild ancestor of cultivated rice, as well as other wild rice species, in Oryza glaberrima and weedy rice were demonstrated to confer enhanced tolerance to water stress, while screenings of cultivated rice germplasms identified several genes/loci improving water stress resistance. New frontiers are represented by the dissection of the epigenetic control of stress tolerance and the implementation of the contribution of favorable microbiota. Innovative breeding technologies, whose feasibility is related to advancements in genomic analyses, are contributing to enhancing the knowledge-based development of water stress-tolerant rice varieties.