Níquel e selênio no controle da ferrugem asiática (Phakopsora pachyrhizi Syd. & P. Syd.) e seus efeitos bioquímicos na cultura da soja

Abstract

Micronutrients can be used as a new technology in the management of Asian rust (Phakopsora pachyrhizi) in soybeans, since mineral nutrients are directly involved in the activation of defense mechanisms, such as enzymatic activators, inhibitors and metabolism regulators. In this context, the objective of this work was to evaluate the effect of nickel and selenium with and without association with a fungicide (azoxystrobin + benzovindiflupir) in the control of the fungus P. pachyrhizi and its effects on the agronomic and biochemical components and productivity in the culture of soy. Two tests were carried out, conducted simultaneously from October 14, 2020 to February 28, 2021, at the Experimental Farm of the Faculty of Agricultural Sciences (FAECA) of the Federal University of Grande Dourados (UFGD) - Dourados-MS. In trial one, the cultivar sw Briza RR was used and the experimental units were composed of six soybean sowing lines (in both trials). For the evaluations, the two central lines were considered. The tests were conducted in a randomized block design, in a 6x2 factorial scheme, totaling 12 treatments. In the first trial, the treatments were: with nickel (Ni) and Ni associated with the fungicide (azoxystrobin + benzovindiflupir), with Ni concentrations (0; 20; 40; 60; 80 and 100 g ha-1) using nickel (NiSO4(H2O)6, and with a concentration of 200 g ha-1 of commercial fungicide, applied during the soybean phenological stage R1. In the second trial, the cultivar used was Monsoy 6410 IPRO, and the treatments were: selenium ( Se), and Se associated with the fungicide, at concentrations (0; 10; 20; 30; 40 and 50 g ha-1) using sodium selenite (Na2SeO3) and associated or not with the fungicide (azoxystrobin + benzovindiflupir), in dose and time specified in the experiment with Ni. The following were evaluated in both experiments: chlorophyll index (SPAD), severity (SEV), area under the disease progress curve (AUDPC), agronomic components and soybean yield, catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), lignin (LIG), cellulose (CEL) and hemicellulose (HEM) and leaf nitrogen (N). Ni application reduced SEV and AUDPC. At 1000G, PROD, GL, AP and SPAD Index - 1 and 2, there were no differences between Ni treatments, and Ni associated with the fungicide, there was no significant effect on the factors, dose, interaction between dose and treatment and block. Ni associated with the fungicide reduced severity by 43.39% compared to Ni, and showed lower AUDPC indices and lower severity compared to Ni. Ni and Ni associated with the fungicide stimulated the production of structural components in the cell wall, such as cellulose, hemicellulose and lignin. There was a significant interaction between the factors, dose and treatment, both for Ni and for Ni associated with the fungicide for the nitrogen content in soybean trefoils. The CAT, POD, SOD, PROT enzymes showed a quadratic fit in the Ni and Ni treatment combined with the fungicide, indicating an increase in activity up to a concentration close to 40 g of Ni ha-1, with an increase in higher concentrations there was a decrease subsequent enzyme and PROT in the tested treatments. For the mass of 1000G, there were no significant differences in Se, and in Se associated with fungicide. For the variable AP, with the increase in the dose of Se and Se associated with the fungicide, there was a negative linear effect, with lower plant height at the dose of 50 g ha-1. The same was observed in SPAD-1. The treatments of Se, and Se associated with the fungicide led to an increase in the CEL and HEM contents, responding with a linear adjustment to the treatments. The CAT, POD, SOD and PROT enzymes showed quadratic adjustment for the treatment of se and selenium combined with the fungicide, indicating an increase to the maximum point, followed by a decrease in enzymatic activities and total protein in soybean trefoils, which may be caused by the toxic effect of Se.