Aplicações foliares de tetraaminoetanol de cobre no manejo da antracnose em soja

Abstract

Soybean (Glycine max (L.) Merril), belonging to the Fabaceae family, is the main grain crop produced in Brazil. Among the factors that limit soybean yields is the occurrence of diseases, such as anthracnose, whose etiological agent is the fungus Colletotrichum truncatum. This disease causes significant losses in crops and can occur from planting until the end of the crop cycle. Among the most used control measures, chemical control stands out in its efficiency in the management of soybean diseases, and the use of copper fungicides is an alternative anti-resistance strategy. The objective of this work was to evaluate the effect of copper tetraaminoethanol in the management of anthracnose in soybeans and in the defense mechanisms of the plant against the pathogen. The product was evaluated at different doses with isolated applications and in association with the fungicide fluxapyroxad + pyraclostrobin in plants at the V7 stage. The experiments were conducted under in vitro and greenhouse conditions. The in vitro experiment evaluated the efficacy of tetraaminoethanol tested at different doses in reducing C. truncatum mycelial growth, spore production and spore viability. For the experiment conducted in the greenhouse, copper was applied and 3 days after the application, the pathogen inoculation was performed. The severity of the disease on the plants was evaluated weekly after the occurrence of the first symptoms. After the application of the products, leaves were collected at different times (after application of the product and after inoculation of the pathogen) to quantify the activity of the enzymes phenylalanine ammonia-lyase (PAL), peroxidase (POX) and polyphenol oxidase (PPO) and the levels of total soluble phenolic compounds and soluble lignin. The design used in the in vitro was completely randomized with 6 replications and in a greenhouse, randomized blocks with 4 replications. Copper tetraaminoethanol in isolated doses inhibited C. truncatum sporulation in Petri dishes, but did not inhibit mycelial growth. The product in doses of 2 mL and 3 mL ha-1 it controlled the severity of anthracnose in the greenhouse, increased the activity of PAL and PPO enzymes and the production of soluble lignin in the plants. It is suggested that the copper tetraaminoethanol acted in a protective manner on the leaves, inhibiting sporulation and colonization, and presented a systemic effect on plants, contributing to the activation of constitutive defense mechanisms.