Diversidade e potencial de utilização de bactérias fixadoras de N2 em Brachiaria brizantha

Abstract

The objective of this research was to analyze the diversity of nitrogen fixing bacteria associated and endophytic B. brizantha, study the potential the solubility of inorganic phosphates of iron and aluminum, produce acid-3-indole acetic (AIA) and to evaluate the effect of inoculation of these isolates in Brachiaria brizantha cv MG 05 Victoria. The bacteria were isolated from soil samples grown under Brachiaria and parts of plant tissue this grass, the dry and wet periods in the municipalities of Alfenas and Machado, southern Minas Gerais. Five semisolid culture media and semi-selective were used: FAM (Azospirillum amazonense), JMV (Burkholderia sp.), JNFb (Herbaspirillum spp.), LGI (A. amazonense) and NFb (Azospirillum spp.). The phosphate solubilization tests and AIA production were performed in vitro and were used as of 22 bacterial isolates selection criteria used in the inoculation of B. brizantha cv MG 5 Victoria, grown in pots containing 20 dm3 of soil. There were two cuts, in what form evaluated the following parameters: height (Al), width (LF) and leaf length (CF), number of tillers (NP), length (CR) and root dry mass (MSR) dry matter (DM), dry matter yield (PMS), neutral detergent fiber (NDF) and acid (ADF) and crude protein in dry matter (PBMS). A total of 332 isolates were obtained, most endophytic. The greatest number and diversity were from the city of Alfenas. During the rainy season was verified greater number and diversity of isolates in both municipalities, when compared to the dry season. Thirty-five isolates solubilized iron phosphate and 78 produced AIA, especially the isolated UNIFENAS 100-17, 21, 40 and 78, able to do both simultaneously. The inoculation of nitrogen fixing strains of endophytic origin and rhizospheric influenced the development of B. brizantha cv MG 5 victory, contributing to the production of MS, PMS and PBMS in the two cutting heights highlighting the UNIFENAS-100-16 isolated, 21, PBMS 78 whose content was more than 7%.