Abstract

For decades, Rhizobia were described as the single inhabitant of legume nodules. However, other bacteria, which are not typical rhizobia, are often found within nodules and suggested to affect the behaviour and fitness of the host plant. Here, we highlight their diversity, role in the promotion of legumes growth and in the recuperation of degraded soils. Studies have shown the capacity of Non-Nodular Endophytic Bacteria to stimulate plant growth by direct mechanisms including production of phytohormones such as auxins, facilitation of acquisition of plant resources/nutrients that plants lack such as fixed nitrogen, iron, phosphorous, besides, production of the enzyme 1-aminocyclopropane-1-carboxylate involved in reduction of plant ethylene, etc. Among the indirect mechanisms, those associated to the enhancement of plant growth are production of siderophores, antibiotics and lytic enzymes. Finally, we described greenhouse and field experiments that successfully used NNEB to both increase the growth and yield of legumes and to recover degraded soils.