Plant growth promoting potential of endophytic Aspergillus niger 9-p isolated from native forage grass in Pantanal of Nhecolândia region, Brazil

Abstract The use of plant growth-promoting fungi (FPCP) is a more environmentally friendly strategy than the use of fertilizers and pesticides in the field. These beneficial fungi have direct and indirect mechanisms that promote plant growth and protection. This study aimed to biochemically characterize the fungal Aspergillus niger 9-P isolated from native forage grass in the Pantanal of Nhecolândia region, concerning the production of molecules responsible for the direct and indirect promotion of plant growth. The production of indole-3-acetic acid (IAA) was determined in relation to different physical-chemical parameters, phosphate solubilization, and production of siderophores by qualitative and quantitative methods. In addition, we investigated the production of ammonia, acid 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and enzymes such as phosphatases, proteases, and other hydrolases (amylase, CMCase, pectinase, and xylanase) of agricultural interest. A pot experiment using common bean plants was carried out in a greenhouse for 30 days to evaluate the effect of the isolate on promoting plant growth. Briefly, the fungus showed the production of IAA (32.65 ± 1.26 μg mL-1), siderophores (88% of siderophore units after 10 days), and high phosphorus solubilizing activity (1138.85 μg mL-1). The isolate synthesized ACC deaminase, produced ammonia, and all other enzymes evaluated in this study. In addition, the results indicated that inoculation with the isolate provided higher values of height and fresh and dry mass of the aerial part and the root compared with the non-inoculated treatment of the common bean plant. The results of this study suggest the potential of the isolate A. niger 9-P for the formulation of biofertilizers aimed at promoting plant growth.