Diversidade fenotípica de bactérias nodulíferas de solos da caatinga associadas a Enterolobium contortisiliquum (Vell) Morong

Abstract

Nodular bacteria are able to carry out biological nitrogen fixation and establish complex interactions, which can be specific or common with their host plants. These symbionts form an ecological group and are commonly known as rhizobia, containing representatives of different genera, among them, the best known are: Rhizobium, Bradyrhizobium, Azorhizobium, Ensifer and Mesorhizobium. The Caatinga is an exclusively Brazilian biome, which has a high degree of biological diversity, which can represent a very promising ecosystem for the prospection of efficient rhizobia in the BNF process. The Fabaceae is one of the most important families in tropical forest biomes, due to its diversity of species, large number of individuals and the ability to associate with different species of rhizobia, attributing to them the ability to capture most of the nitrogen necessary for their growth, directly from the atmosphere, through this mutualistic relationship. The aim of this study was to evaluate the phenotypic diversity of bacteria associated with Tamboril (Enterolobium contortisiliquum) nodules. The 45 nodules isolated in this research came from a capture test previously carried out on soil samples from four areas of Caatinga in the state of Alagoas. The nodules were submitted to a process of maceration and bacterial suspension inoculated in YMA culture medium and after growth their cultural characteristics were tabulated, such as: growth time, pH change, colony color, mucus production and consistency. The nodulation capacity of the isolates was evaluated through an authentication test using the plant under study. After 60 days of plant germination, nodulation was evaluated, 29 bacteria were isolated, which formed 10 phenotypically diverse groups. There was a predominance of slow-growing isolates, corresponding to 58.62% of the collection, while fast-growing isolates accounted for 41.37%. All isolates showed the ability to establish a specific interaction with Monkfish, confirmed by the formation of root nodules in the plants. It is concluded that all soil samples used to capture rhizobia present phenotypically diverse populations of native noduliferous bacteria capable of nodulating Enterolobium contortisiliquum, and may have promising potential as inoculants, as they are adapted to the edaphoclimatic conditions of the Caatinga biome.