The inoculation with Nitrospirillum amazonense through the activity of biological nitrogen fixation (BNF) and production of phytohormones, causes changes in the availability of nutrients in the soil and in the architecture of the root system of sugarcane, which may affect the competitive capacity of pre-fertilized seedlings. -sprouted (MPB) to weed species, and the use of pre-emergent herbicides used in the crop can have a toxic effect on bacterial cells. Thus, this work will aim to evaluate the impact of inoculation with Aprinza (N. amazonense) on the competitiveness of sugarcane MPB's, as well as the effect of weed competition on the rhizospheric microbiota, and to evaluate the toxicity of pre-emerging herbicides to bacterial cells. In the first test, three weed species (Merremia aegyptia, Urochloa decumbens and Cyperus rotundus) will be evaluated at 4 densities (10, 20, 40 and 80 plants m2), coexisting with MPB's in the presence and absence of inoculation with Aprinza (N.amazonense ), in addition to controls (weed only and MPB only, with and without inoculation). At 150 days after planting (DAP) the seedlings will be evaluated in relation to height (cm), leaf area (cm2), dry biomass of the aerial part (g), length (cm) and dry biomass of the root (g). Still at 150 DAP the rhizospheric soil will be evaluated in relation to bacterial and fungal diversity through metagenomic analysis of the soil, through DNA extraction and sequencing, targeting the 16S rDNA region of bacteria and the intergenic ITS region of fungi, and in in relation to microbial activity, through the analysis of the activity of ²-glucosidase and arylsulfatase enzymes, through the p-nitrophenol quantification method. To evaluate the toxicity of herbicides to N. amazonense bacteria, four in vitro assays will be performed. In the first in vitro test, ten pre-emergent herbicides registered for sugarcane (clomazone, imazapic, tebuthiuron, indaziflam, s-metalachlor, metribuzin, isoxaflutole, sulfentrazone, flumioxazin) will be evaluated for their minimum inhibitory concentration (MIC). The herbicides will be evaluated in 5 doses (1/4DC, 1/2DC, DC, 1.5DC, 2DC), in addition to controls without herbicide. In the second in vitro test, the resistance of N. amazonense to the application of the same herbicides in the soil will be evaluated, through the quantification of the Most Probable Number (MPN) of N. amazonense g. solo-1 using the McCrady table. In the third test, the herbicides will be evaluated at the commercial dose for the impact on the BNF capacity of the N. amazonense bacteria. For this, bacterial cells will be evaluated in N-free NFb semi-solid medium by the semi-micro Kjeldahl digestion method. In the fourth in vitro assay, N. amazonense cells will be evaluated for the impact of herbicides on the ability to inhibit the production of indole-acetic acid (IAA). Ten herbicides will be evaluated at the commercial dose. Bacterial cells will be subjected to the AIA production test by adding Salkowiski's reagent. The data from the experiments will be submitted to analysis of variance and, when significant, the means will be compared by Tukey's test at 5% probability.
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