Fungos da caatinga e seu potencial na promoção da fertilidade do solo de áreas em processo de desertificação

Abstract

The Caatinga domain has a rich and poorly studied soil microbiome, which is only now beginning to be unveiled with metagenomic approaches. Despite this advance, there is a gap about the knowledge of fungal diversity of the soil in desertification nuclei in the semiarid region and its potential for technological recovery of degraded areas. In this context, this study aimed to isolate and evaluate the potential of fungi from Caatinga soils in order to select promising strains for the development of inoculants that can be used to mitigate the effects of desertification. For this, soil collections were carried out in three different landscapes in the desertification nucleus of Irauçuba, Ceará. Two highly degraded pasture areas, two areas surrounded for 18 years, in the process of natural regeneration and an area of natural vegetation were sampled. The soil samples were diluted serially (10−1 to 10−8) in 0.15 M NaCl solution and the dilutions were plated in triplicates, in Potato Agar plates and stored at room temperature. The plates were daily inspected and after the colonies had grown, the characteristics of the morphotypes were captured using a magnifying glass. As a result, 22 morphotypes were selected and preserved as pure cultures in distilled water at 4 ºC. The morphotypes were evaluated for there potential in phosphate solubilization and siderophores prodution, important activities for plant fertility. The molecular identification of the isolates was performed by sequencing the intergenic region ITS1 and ITS4 by the Sanger method. The obtained sequences were treated in the Geneious R10 program and the genera and species identified through comparisons with reference sequences deposited in public banks. Of twenty-two morphotypes analyzed, 33% showed phosphate solubilization activity and 64% siderophores production. Among the isolates, six stood out with four of them coming from the natural recovery areas and two from the natural vegetation area. Based on the criteria of good phosphate solubilization and siderophores production, three isolates were selected as the most promising. No isolates from desertified areas were selected based on these criteria. The three isolates were identified as Aspergillus spp. The results of this study represent the first step towards the discovery of new fungi strains adapted to the semiarid conditions and potential candidates for inoculants able to accelerate the recovery of degraded soils.