The arbuscular mycorrhizal fungus Rhizophagus clarus improves physiological tolerance to drought stress in soybean plants

Abstract

Soybean (Glycine max L.) is an economically important crop, and is cultivated worldwide, although increasingly long periods of drought have reduced the productivity of this plant. Research has shown that inoculation with arbuscular mycorrhizal fungi (AMF) provides a potential alternative strategy for the mitigation of drought stress. In the present study, we measured the physiological and morphological performance of two soybean cultivars in symbiosis with Rhizophagus clarus that were subjected to drought stress (DS). The soybean cultivars Anta82 and Desafio were grown in pots inoculated with R. clarus. Drought stress was imposed at the V3 development stage and maintained for 7 days. A control group, with well-irrigated plants and no AMF, was established simultaneously in the greenhouse. The mycorrhizal colonization rate, and the physiological, morphological, and nutritional traits of the plants were recorded at days 3 and 7 after drought stress conditions were implemented. The Anta82 cultivar presented the highest percentage of AMF colonization, and N and K in the leaves, whereas the DS group of the Desafio cultivar had the highest water potential and water use efficiency, and the DS + AMF group had thermal dissipation that permitted higher values of Fv/Fm, A, and plant height. The results of the principal components analysis demonstrated that both cultivars inoculated with AMF performed similarly under DS to the well-watered plants. These findings indicate that AMF permitted the plant to reduce the impairment of growth and physiological traits caused by drought conditions.

Arbuscular Mycorrhizal Symbiosis: A Strategy for Mitigating the Impacts of Climate Change on Tropical Legume Crops

“…As a result of reduced photosynthesis under drought conditions, legume growth and yield are strongly inhibited. Reduction in various growth and yield parameters were also reported in drought-stressed green bean [ 62 ], soybean [ 21 , 60 , 61 ], and chickpea [ 65 ] plants ( Table 1 ).…”

“…Legumes respond directly to drought stress by triggering stomatal closure to prevent water loss through transpiration. This is evident from studies on soybean and green bean that reported a decrease in stomatal conductance and transpiration rate during a drought stress treatment [ 21 , 62 ]. Stomatal closure limits the CO 2 intake and subsequently inhibits photosynthesis.…”

“…Stomatal closure limits the CO 2 intake and subsequently inhibits photosynthesis. In a drought treatment, a drought-sensitive soybean cultivar Anta82 experienced reduced photosynthesis rate after 3 days [ 21 ]. As a result of reduced photosynthesis under drought conditions, legume growth and yield are strongly inhibited.…”

“…AMF colonize plant roots and develop an extensive network of extraradical hyphae in the soil surrounding the root, which help to absorb water from the soil [ 97 ] and enhance water uptake under drought conditions. Higher stomatal conductance, transpiration, and photosynthesis rates occurred in AMF-associated legumes such as soybean and green bean [ 21 , 62 ] ( Table 1 ). AMF treatment on legumes is also beneficial for the uptake of nutrients: When administrated with 45% to 75% water holding capacity, mycorrhizal green bean plants had increased macro- and micronutrients including N, P, K, Mg, Fe, zinc (Zn), manganese (Mn), and copper (Cu) [ 63 ].…”

“…One prime example is the arbuscular mycorrhizal fungi (AMF), which are natural root symbionts that are commonly referred to as bio-fertilizers [ 19 , 20 ]. Several studies have demonstrated that inoculating legumes with AMF boosts their resistance to abiotic stresses such as drought, heat, salinity, and extreme temperatures [ 21 , 22 ]. AMF may aid in the upregulation of tolerance mechanisms in host plants while also preventing the downregulation of key metabolic pathways [ 23 ].…”