Ocorrência e potencial simbiótico de populações de rizóbios nativas de solos do semiárido

Abstract

The use of nitrogen-fixing bacteria through the rhizobium-legume symbiosis is a sustainable baseline solution to reduce potential environmental impacts caused by the use of industrialized fertilizers and the burning of fossil fuels. For this, it is necessary to select efficient rhizobia adapted to the edaphoclimatic conditions of each region. Thus, this work aimed to evaluate the occurrence and symbiotic potential of the bean rhizobia populations naturally established in semi-arid soils. In order to capture the isolates, areas with dense caatinga cover (with little anthropic interference) and the main soil classes occurring in the biome were selected: Argissolo, Neolithic, Quartzarenic Neosol, Regolithic Neosol, Latosol, Luvisol and Planosol of different municipalities located in Agreste and Sertão de Pernambuco. A randomized block experiment with three replicates was conducted. The species used as plant-bait was cowpea (Vignaunguiculta (L.) Walp), BRS Pujante variety. Five nodules were randomly chosen from each replicate to proceed to isolation. After the isolation and growth of the isolated colonies, the morphophysiological characterization of the isolates was evaluated, evaluating the reaction of pH in culture medium, growth time and exopolysaccharide production. Bean Cowpea developed normally, presenting 100% survival. For nodulation, in all soil classes studied, populations of rhizobia capable of nodulating the crop were observed. 338, mostly fast growing, were included that acidify the culture medium and have a lot of mucus. The characteristics have been used for these noduliferous species of different species of legumes natives of semi-arid regions of Brazil.