Bioprospecção de fungos rizosféricos associados à cactáceas em área de processo de desertificação para promoção de crescimento em plantas

Abstract

Over time, cacti have acquired mechanisms to establish themselves in scarce water and nutrient environments. The objective of this study was to isolate and identify rhizospheric fungi in association with cacti (Opuntia cochenillifera) that occur spontaneously in an area under exponential salinization and desertification, as well as to model their chemical and mineralogical attributes and to perform bioprospecting of the isolated fungi and their capacity as growth promoters in plants. To determine the microbial population, soil collection was performed at a depth 0-20 cm from the surface in the area corresponding to the rhizosphere. The dilution was carried out up to the fraction 10-3, 10-4 and 10-5 and inoculated in Petri dishes containing selective culture media and the counting of colony forming units (CFU) and the morphological and molecular identification of the isolated strains were performed. It was possible to observe the presence of rhizospheric fungus in association with O. cochenillifera, in an area undergoing desertification and salinization. Through comparison (e-value> 99%), similarities for Aspergillus spp. (isolate F02) and Coprinellus spp. (isolate F05). the strains were subjected to phosphate solubilization assays, production of 3-indole acetic acid (IAA), antagonism against phytopathogenic fungi, cucumber seedling development and growth in water-restricted culture medium. Finally, an in vivo test was carried out to promote growth in association with silicate rock powder. All test results were subjected to statistical analysis and averaging or regression testing, when appropriate. These species are known in the literature for their metabolic richness, being applicable to biotechnological processes to promote growth in cultivated plants. The strains studied were able to solubilize phosphate, being F04 and F05 the ones with the highest solubilization rates. As for the production of IAA, the strains F02 and F07 were the most promising, with values above those stipulated to check as highly producers, although all strains have produced the hormone, even at lower levels. All strains studied were able to inhibit the growth of Colletotrichum sp. and Fusarium sp., with rates above 80% of mycelial growth inhibition, acting by mechanisms of direct confrontation, overlap or production of metabolites. The development of cucumber seedlings was evidenced for strains F07, F08, F09 and F10, as well as for radicle emission. The water restriction provided the mycelial growth of the strains, with a decrease from the concentration of 10%. Growth promotion was verified in vivo with and without association with silicate rock powder. Therefore, these characteristics give these strains growth-promoting characteristics in plants.