Potencial de controle in vitro de fungos e nematóide, isolados do morango, por extratos de Calendula officinalis em diferentes concentrações

Abstract

The strawberry, Fragaria x ananassa Duch., due to its high perishability comes receiving a high load of chemical and synthetic products, increasing the number of researches related with the use of alternative products in the cultivation. The calendula, known for its therapeutic potential, is being tested in the agricultural environment with the intention of determining its potential to protect the phytopathogenic agents that could attack agricultural crops. Due to the small number of studies involving the use of calendula in agriculture, the present study aimed to investigate, in vitro, the fungicidal potential against Colletotrichum acutatum and Botrytis cinerea as well as the nematicides potential on Meloidogyne hapla. To do so, were prepared, separately, the aqueous crude roister extract (EBAFO) and chapters (EBACA) of calendula, both 10%. In the trial that assessed the fungicidal activity, the concentrations of 0% (control); 1,25%; 2,5%; 5% and 10% of EBAFO and EBACA, were mixed, individually, in the middle of PDA (potato dextrose agar) flux cultivation. The experimental design used was completely randomized (CRD), with 5 treatments and 4 repetitions. It was evaluated the mycelial growth of fungi until one of the treatments have reached the edge of the plate, when was also evaluated the sporulation in the Newbauer chamber. For the evaluation of the nematicide potential, were used the concentrations of 0% (control); 6,25%; 12,5%; 25% and 50% with the same design, where after obtaining the eggs, they were placed in microtiter plates (ELISA type), and the outbreak was evaluated at 12 days. The data were submitted to analysis of variance with the help of the statistical software SASM – Agri and averages submitted to regression analysis with the help of the Excel Spreadsheet, where the following variables were analyzed: extract/mycelial growth; sporulation/extract; extract/outbreak. The results obtained demonstrate that the EBACA has an inhibitory effect on the fungus B. cinerea, for which the concentration of 5% and 10% were the most inhibited in the mycelial growth compared to the control. In the trial with EBAFO, the treatments stimulated the mycelial growth compared to the control. In front of the fungus C. acutatum, fungistatic effect was not observed in any of the concentrations of both extracts tested, but rather a gradual stimulating effect in most of the treatments compared to the control, with the difference reaching 1,4 cm with the implementation of the extract of chapters and 4,2 cm for the roister. There was no significant difference among the treatments, when was evaluated the sporulation of both pathogens. Different concentrations of the extracts derived from the chapters and leaves of C. officinalis exerted a significant effect on the outbreak of J2 in relation to the control, being possible to observe a reduction in the percentage of the outbreak compared with the control already in the lowest dose of the extract (6,25%).