Root Phenotyping: A Contribution to Understanding Drought Stress Resilience in Grain Legumes

Global climate change predictions point to an increase in the frequency of droughts and floods, which are a huge challenge to food production. During crop evolution, different mechanisms for drought resilience have emerged, and studies suggest that roots can be an important key in understanding these mechanisms. However, knowledge is still scarce, being fundamental to its exploitation. Plant-based protein, especially grain legume crops, will be crucial in meeting the demand for affordable and healthy food due to their high protein content. In addition, grain legumes have the unique ability for biological nitrogen fixation (BNF) through symbiosis with bacteria, which contributes to sustainable agriculture. The exploitation of root phenotyping techniques in grain legumes is an important step toward understanding their drought resilience mechanisms and selecting more resilient genotypes. Different methodologies are available for root phenotyping, including the paper pouch approach, rhizotrons and the semi-hydroponic system. Additionally, different imaging techniques have been employed to assess root traits. This review provides an overview of the root system architecture (RSA) of grain legumes, its role in drought stress resilience and the phenotyping approaches useful for the identification of accessions resilient to water stress. Consequently, this knowledge will be important in mitigating the effects of climate change and improving grain legume production.