Ação de Pseudomonas fluorescens sobre fungos de solo e como promotora de crescimento com a associação de Azospirillum brasilense em plantas de soja

Abstract

Soybean (Glycine max) is the main grain-producing crop among legumes, being a commodity of great importance in the world economy, as it provides raw material to various industries, mainly for animal and human feeding. Among the main factors that affect crop yields are diseases caused by different phytopathogens, and the use of chemicals, in addition to losing their efficiency, have an environmental appeal to reduce use. In view of this reality, it is necessary to be adhering to more sustainable management alternatives, such as the use of biocontrol agents. For this, it is importante to study promising microorganisms such as the rhizobacteria Pseudomonas fluorescens and Azospirillum brasilense that act beneficially in association with plants, promoting their growth and solubilizing nutrients present in soils, besides presenting antagonistic potential on soil fungi. In this sense, two experiments were developed, the first with the objective of evaluating the potential of the rhizobacterium Pseudomonas fluorescens in the in vitro control of soil phytopathogens Fusarium tucumaniae, Macrophomina phaseolina, Sclerotinia sclerotiorum, Phomopsis longicolla and Rhizoctonia solani that affect soybean culture. In the second experiment, we sought to evaluate the efficiency of Pseudomonas fluorescens in association with Azospirillum brasilense in promoting soybean plant growth. The in vitro experiment was carried out in the biochemistry laboratory of the Federal Technological University of Paraná- Campus Dois Vizinhos, following the method of direct confrontation by pairing. Composed of ten treatments, being T1; T2; T3; T4 and T5 (Witnesses with pathogens) and T6= Pseudomonas fluorescens + Fusarium tucumaniae; T7= Pseudomonas fluorescens + Macrophomine phaseoline; T8= Pseudomonas fluorescens + Sclerotinia sclerotiorum; T9= Pseudomonas fluorescens + Phomopsis longicolla and T10= Pseudomonas fluorescens + Rhizoctonia solani. The experimental design adopted was completely randomized (IHD), with four replications. The mycelial growth of fungi and the formation of inhibition halos every 24 h, lasting 192 hours, were evaluated. In the second experiment, to evaluate the performance of rhizobacteria as growth promoters, seeds were inoculated, and they were sowed in PCV tubes of 200mm x 70cm, containing substrate. The experiment consisted of four treatments, t1= control; T2= Azospirillum brasilense; T3= Pseudomonas fluorescens and T4= Azospirillum brasilense + Pseudomonas fluorescens. Following IHD as an experimental design, with four replications. The aerial length, root system length and green mass of the shoot and root system were evaluated. The results were submitted to Lilliefors normality test, after variance analysis (ANOVA) and the means grouped by Tukey test at 5% probability. In general, under the conditions of the present study, the bacterium Pseudomonas fluorescens showed a reduction in mycelial growth only of Fusarium tucumaniae.And it showed promising results in promoting soybean growth when associated with Azospirillum brasilense.