Uso de fosfito de potássio no controle de Sclerotium rolfsii

Abstract

The fungus Sclerotium rolfsii is an important pathogen that attacks seedlings and plants in both monocotyledonous and eudychotyledonous cultures, being difficult to control and for this reason many researches are carried out with alternative products to combat fungus. The objective of this work was to evaluate the effect of the in vitro potassium phosphite control of Sclerotium rolfsii on seed germination and the incidence of S. rolfsii in soybean seedlings. The experimental design was completely randomized with five doses and five replicates. The variables analyzed were: in vitro mycelial growth of fungus S. rolfsii, percentage of seed germination and incidence of S. rolfsii in soybean seedlings. For the in vitro test the potassium phosphite was added in the BDA culture medium at the concentrations of 0, 2, 4, 6 and 8 mL. L-¹. Afterwards a mycelial disc of the fungus was placed in the center of the Petri dish containing the BDA medium plus the phosphite and evaluated the mycelial growth in the different doses. For the treatment of soybean seeds, concentrations of 0, 2, 4, 6 and 8 μL potassium phosphite were used for 100 g of seed and seeded in gerbox boxes filled with 100 g of substrate colonized with S. rolfsii and evaluated germination and incidence of fungus in soybean seedlings. The results were submitted to analysis of variance by the F test (p≤0.05), and the regression test was performed, at a 5% probability level. Potassium phosphite reduces the incidence of S. rolfsii in soybean seedlings and promotes reduction of mycelial growth rate in vitro, and the highest reduction in the incidence and in vitro control levels was in the concentration of 8 mL L-¹, with 85.74% and 42.8%, respectively. The use of potassium phosphite improves the germination of soybean seeds up to the dose of 5.6 μL / 100g-¹ seeds, and is not phytotoxic until this dosage.