LAUSR

ABSTRACT Legumes are well recognized for their nutritional and health benefits as well as for their impact in the sustainability of agricultural systems, due to their ability to form a symbiosis with N2-fixing microorganisms. Nevertheless, legume N2 fixation has a high energy cost, and phosphorus (P) deficiency strongly hampers legume production, especially in low-P soils typical of most of the tropical regions. P-deficiency limits N2 fixation, since it has been described to have a strong impact on the growth and survival of both rhizobia and host plant. Legumes have evolved strategies at both morphological and physiological levels to adapt to P-deficiency. The maintenance of symbiotic N2 fixation seems to be a key aspect to assure legume productivity in low-P environments. During the last decades, physiological components and molecular players underlying P-deficiency adaptation responses have been elucidated. Hence, in order to design strategies to develop elite cultivars able to produce high-quality seeds and efficiently fix N2 under P-deficiency, it is important to understand how legumes cope with this nutritional constraint. In this review, we discuss future directions and research priorities that may lead to a better understanding of the physiological and molecular adaptations that allow the legumes to thrive under conditions of P-deficiency.