Influência de fatores abióticos sobre o desenvolvimento de bactérias promotoras de crescimento vegetal dos gêneros Bacillus e Pantoea

Abstract

Incorrect handling during the application of most agricultural pesticides has been causing contamination in soils, groundwater, fauna and flora in Brazilian agroecosystems, in addition to increasing costs in agricultural production. The microbiota when subjected to dosages above the recommended level of certain pesticides suffers deleterious effects on their populations. And as a way to reduce input costs and the search for more sustainable agricultural production, the use of growth promoting bacteria and bioremediators is a biotechnological tool of great potential. Another factor that influences agricultural production is salinity. It is a term that qualifies a situation of excess soluble salts in the environment. This problem is one of the main causes of soil degradation in regions of arid and semi-arid climate, culminating in serious agricultural income. To contribute to the recovery of these degraded soils, plant growth promoting bacteria have been shown to be useful in the development of strategies to promote plant growth in saline soils. In view of the above, the present work had as objectives: i) to evaluate the tolerance to the methomyl pesticide and the potential biodegradation capacity of this pesticide by Bacillus plant growth promoting bacteria; and ii) to evaluate the production of exopolysaccharides under saline stress by plant growth promoting bacteria of the genus Pantoea. For the evaluation of pesticide tolerance, the Bacillus bacteria (UAGAT35 and UAGAT71). were inoculated in modified Minimal Mineral Medium (MMM), plus glucose as carbon source, followed by different concentrations of Methomyl. And to assess the potential for biodegradation, the carbon source has not been increased. In the experiment on salinity, five bacterial strains of the genus Pantoea were used (UAGC 906, UAGC 977, UAGC 858, UAGC 907 and UAGC 972), which were grown in solid medium with sucrose and added different concentrations of NaCl in each tr. For 10 days, the growth of the halo was measured with the aid of a pachymeter, being done five readings, in intervals of 48 hours. The two strains of the genus Bacillus demonstrated tolerance and biodegradation to methomyl insecticide, in their different concentrations. While the 5 bacterial strains of the genus Pantoea submitted to the different concentrations of NaCl presented production of Exopolysaccharides (EPS), showing their survival in environments under IX salt stress. Therefore, the evaluated bacteria presented potential for future studies aiming to promote growth in adverse environments.