Diversity of Rhizobia and Importance of Their Interactions with Legume Trees for Feasibility and Sustainability of the Tropical Agrosystems

Abstract

Symbiotic biological nitrogen fixation (BNF) is a complex process that involves rhizobia, a diverse group of α and β-proteobacteria bacteria, and legume species. Benefits provided by BNF associated with legume trees in tropical environments include improvements to efficiency of nitrogen (N) use, increase of soil carbon sequestration, stabilization of soil organic matter, decrease of soil penetration resistance, and improvement of soil fertility. All these benefits make BNF a crucial ecosystem service to the sustainability of tropical agriculture. Due to the importance of this ecological process and the high diversity of rhizobia, these bacteria have been extensively characterized worldwide. Currently, over 400 species of rhizobia are known, distributed into seven families. In the humid tropics, Leucaena leucocephala, Acacia mangium, Gliricidia sepium, and Clitoria fairchildiana are four of the most common species used by family farmers to create sustainable agricultural systems. These four legumes perform symbiosis with different groups of rhizobia. Exploring BNF could help to enable sustainable intensification of agriculture in the humid tropics, mainly because it can increase N use efficiency in an environment where N is a limiting factor to plant growth.

More diverse rhizobial communities can lead to higher symbiotic nitrogen fixation rates, even in nitrogen-rich soils

“…This differs markedly from our expectations and contrasts with evidence from the agricultural literature that co-inoculation only impacts SNF in N-limited conditions [15]. If high rhizobial diversity induces ‘luxury fixation’ in legumes over large spatio-temporal scales in nature, it could provide a potential mechanism for ecosystem N surpluses such as those seen in many tropical forests [41] that harbour high rhizobial diversity [42]. Together, these data suggest that rhizobia-driven BEF effects on legume function are not merely scientific novelties, but could have important implications for plant growth and ecosystem N cycling.…”

Rhizobium-Linked Nutritional and Phytochemical Changes Under Multitrophic Functional Contexts in Sustainable Food Systems

“…in Medicago truncatula and Mimosa pudica (Benezech et al, 2020b;Moura et al, 2020). Fungal species such as Cladosporium cladosporioides, Fusarium moniliforme, Fusarium oxysporum, Fusarium solani, Macrophominia phaseolina, and Rhizoctonia solani are known plant pathogens (Walker et al, 2016;Batnini et al, 2020;Chen et al, 2020;Lakhran and Ahir, 2020;Poveda et al, 2020).…”

Physiological responses of black locust‐rhizobia symbiosis to water stress

“…Root symbiosis can partially counteract these negative effects of drought on root functions. In this context, the legume‐ rhizobia symbiosis is of particular significance (Luescher et al, 2014), because it improves not only N nutrition by symbiotic N fixation and P availability in the soil (Du et al, 2018; Moura et al, 2020), but also water acquisition (Belimov et al, 2009). The latter is achieved by enhanced root hair development and lateral root growth, supporting water and nutrient uptake (Dimkpa et al, 2009).…”