Potencial de Beauveria bassiana e metabólitos na indução de resistência e no controle de doenças foliares em soja

Abstract

Soybean cultivation (Glycinemax (L.) Merril) presents great importance in the Brazilian economy and worldwide, however, the high number of pests and diseases in this crop brings significants losses in production. The Beauveira bassiana is widely used in biological controlo of insect pests in soybean crop. However, this fungus and metabolites had been reported with potential of inducing plants resistance against insects and diseases. The objective of this work was to evaluate the potential of B. bassiana and its metabolites in the activation of plant defense and in the control of foliar diseases in soybean crop. The experimente was carried out in the Biological Control Laboratory, Biochemistry and Resistance Induction Laboratory and at the Experimental Station of Universidade Tecnológica Federal do Paraná (UTFPR) Dois Vizinhos Campus, Paraná (PR). The experimental design for all the experiments was completely randomized. In the first work the treatments of B. bassiana, its metabolites and Acienzolar-S-Metil were evaluated in soybean cotyledons. Seeds were planted in trays of polypropylene, having as substratum autoclaved sand. After seven days the cotyledons were removed from the seedlings and washed in destilled water and determined the mass of fresh matter. In the cotyledons abaxial face, superficial cuts were made and above this cuts, the elicitor solutions were deposite or, as control, destilled water. Next, deposited in Petri dishes. The plates were properly closed and unsealed and kept in a BOD chambre at 26oC and no light. After 20 hours, the cotyledons were removed to biochemical analyzes and quantification pf phytoalexins, phenylalanine ammonia-lyase (PAL) enzyme activity and phenolic compounds. With the results from the previous work, it was observed potential of vegetal defense, so, two other studies were developed verifying the potential of this activation in acting effectively in the control of foliar diseases. In order to verify effects on Asian rust and powdery mildew, the in vivo studies were carried out using the detached leaf methodology (FRAC - Fungicide Resistance Action Committee) and also applied to the field. The treatments for these two studies in leaf diseases were B.bassiana, metabolites and the fungicides trifloxystrobin + prothioconzol and copper oxychloride. The results were tabulated, evaluated for normality and the analysis of variance was performed. Results indicated that B.bassiana and metabolites induced resistance in soybean plants, activating the PAL enzyme, the synthesis of phytoalexins and increase in phenolic compounds. However, it has no potential to control leaf diseases rust and powdery mildew in soybean cultivation.