Caracterização e controle alternativo de espécies de fusarium associadas ao damping-off no coentro

Abstract

The incidence of damping off of coriander seedlings limits the production of this vegetable in northeastern Brazil, due to reduced stand. There are still no concrete studies on the specific cause of the disease in culture. However, knowing the etiological agent is essential for the development of control methods. Therefore, the objective of this work was to identify and characterize phytopathogenic agents associated with the damping-off of coriander seedlings in the states of Alagoas, Pernambuco and Ceará, and to evaluate their sensitivity to essential oils of clove, cinnamon, citronella and tea tree. Soils were collected in different coriander producing areas, taken to the laboratory where they were distributed in 300 vases with a capacity of 250mL and identified according to the municipality of collection. To obtain the isolates, six coriander seeds of the Verdão cultivar (Isla seeds LTDA) were sown in each pot. Seed germination occurred seven days after planting and, 10 days after germination, the seedlings showed symptoms of wilting followed by damping off, thus performing the indirect isolation of pathogens. Morphocultural and molecular analyzes were performed with specific primers for RNA polymerase subunit II (RPB2) and elongation factor (TEF-1α) genes. In the test to assess the sensitivity of the F. fabacearum and F. falciforme species, the experimental design was completely randomized (4 essential oils x 5 concentrations), with five replications, with the experimental unit consisting of a Petri dish. Treatments were generated by combining concentrations (0; 12.2; 25; 50; 100 and 200 μL mL-1) of essential oils. The plates were inoculated with the pathogens for seven days at 25 ± 2 °C. To verify the difference between treatments, the mycelial growth velocity index (IVCM) and the mycelial growth inhibition percentage (PIC) were calculated. A total of thirty-eight Fusarium isolates were obtained. Of these, thirty isolates clustered in the F. oxysporum complex (one isolate of F. elaeidis; one isolate of F. gossypinum and twenty-eight isolatesof F. fabacearum) and eight isolates in the F. solani complex, together with the species F. falciforme. In the sensitivity test, cinnamon essential oil was the one that showed the best result from the concentration of 50 μL mL-1 with fungicidal action on mycelial growth for the species F. fabacearum and F. falciforme when compared to the other oils. Based on this, this is the first report of F. fabacearum, F. gossypinum and F. elaeidis causing damping off in coriander seedlings in the world.

Keywords: Coriandrum sativum, Damping-off, Natural fungicide.