Silicato de cobre na indução de resistência para o manejo do oídio (erysiphe diffusa) na cultura da soja.

Abstract

Soybean (Glycine max) is the main commodity of Brazil, and one of the factors that limit its productivity is the occurrence of diseases such as oidium. Soybean oidium, Erysiphe diffusa, is a biotrophic fungus that affects the crop at any stage of plant development and, when not properly managed, can cause losses ranging from 20 to 40%. The control measures adopted for this disease involve the use of resistant cultivars and the application of fungicides. However, the use of mineral elements such as copper and silicon are characterized as an efficient alternative in disease management. These elements have antifungal properties and act inducing plant defense mechanisms. In this context, the objective of the work was to evaluate the effects of copper silicate on soy defense responses and oidium management. Two experiments were carried out in a vegetation house, designed in causalized blocks (DBC). The experiment I aimed to evaluate the antifungal effect of copper silicate against oidium and was installed in DBC, with seven treatments, four repetitions and two plants per plot. The treatments consisted of: a negative control (without application of the product), a positive control with the fungicide registered for disease management (fluxapyroxade + pyraclostrobin), the commercial resistance inducer (Acibenzolar-S-methylASM) and copper silicate in the following doses 2.5, 5, 7.5 and 10 mL/L. The application of the products was carried out in stages V2/V4. Seven days after the application of the products, the plants were inoculated with E. diffusa. The severity of the oidium was evaluated. Experiment II aimed to evaluate the inductive effect of copper silicate and was conducted in BCD, with four treatments and four repetitions. The treatments consisted of: a negative control (without application of the product), a positive control with commercial inductor (ASM) and copper silicate in doses of 5 mL/L and 10 mL/L. The application of the products was carried out in stages V2/V4. For the analysis of the enzymes phenylalanine ammonia-lyase (PAL), superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), chitinase (QUI), lipid peroxidation and phenolic compounds, samples were collected at 0, 24, 48, 72 and 96 hours after application of the treatments. For the quantification of soluble lignin, collection was carried out 14 days after the products were applied. The quantification of the isoflavonoids daidzein and genistein was also performed. The application of copper silicate significantly reduced the progress of soy oidium, with emphasis on doses of 5 and 10 mL/L, which promoted reductions of 27.2% and 34.6% in AACPD, respectively, compared to negative control, in addition to stimulating plant defense responses, with increased activity of enzymes such as PAL, SOD, CAT and chitinase, application of copper silicate promoted a point increase in lipid peroxidacon, compatible with the initial activation of defense mechanisms. The application of copper silicate at a dose of 5 mL/L also resulted in an increase in the content of soluble lignin and isoflavonoids daidzein and genistein. in this way, copper silicate is a promising alternative for the integrated management of soybean oidium, contributing to more sustainable agricultural systems