Plant Stress (Aug 2022)
Symbiotic microorganisms affect the resilience of Hymenaea courbaril L., a neotropical fruit tree, to water restriction
Abstract
Hymenaea courbaril L. is a fruit species widely distributed throughout the Neotropics and possibly tolerant to a range of environmental variations, including adaptation to dry soils. Therefore, we hypothesized that growth-promoting microorganisms isolated from the roots and rhizosphere of this plant affect its resistance to water suppression. We aimed at testing our hypothesis by biopriming the seeds of this species using microorganisms previously tested for the expression of functional traits associated with growth promotion, followed by cultivating this plant under a water deficit regime for three months. The inoculation effect was evaluated in terms of growth parameters, photosynthetic pigments, photochemical performance, and gas exchange. Bacteria, particularly isolates of Bacillus cereus, B. thuringiensis, and Paenibacillus alvei, were more effective than fungi in promoting growth in H. courbaril L. under water suppression. However, the inoculation treatments with B. thuringiensis and Curvularia intermedia minimized the water deficit-induced photochemical damage, with the observed values being similar to or higher than those observed in irrigated plants. In general, microbial inoculation increased the photosynthetic rate and stomatal conductance in leaves, and the C. intermedia and B. thuringiensis inoculation induced the rates of net assimilation and carboxylation efficiency that also exceeded the average observed in irrigated plants. These microorganisms potentially assist H. courbaril L. in its dispersal through water-poor soils and, based on the plant growth-promoting rhizobacterial effect observed in B. thuringiensis, could be applied in agriculture as stress reducers and growth promoters. Aiming the future production of inoculants, we indicate the use of B. thuringiensis and C. intermedia, however, we suggest that phytopathogenicity studies are previously carried out with this endophytic strain of C. intermedia. Alternatively, this work showed the expression of phytopathogenic traits by the rhizospheric fungus Penicillium shearii, possibly stimulated by drought stress conditions.
