ESSENTIAL OILS OF PITANGA AND GOIABA IN THE MYCELIAL DEVELOPMENT AND DEVELOPMENT OF SCLERODES OF Sclerotinia sclerotiorum

The fungus Sclerotinia sclerotiorum has a wide range of hosts, attacking more than 75 families, 278 genera and 408 species of plants, and several of these hosts are weeds. This fungus has the ability to form sclerotia that guarantee its survival under adverse environmental conditions. The effect of metabolites extracted from plants such as essential oils have a potential as natural fungicides inhibiting fungal activity. The objective of this work was to evaluate the effect of essential oils of Pitanga (Eugenia uniflora) and Goiaba (Psidium guajava) under mycelial growth and development of sclerotiorum sclerotia. The work was carried out during the year 2018, in the Phytopathology laboratory of UTFPR - Campus Dois Vizinhos. The essential oils obtained by steam trapping in Clevenger-type equipment, at a concentration of 15μL, were applied on autoclaved filter paper (1cm2) and attached to the top lid of the Petri® plate. A mycelial disc (7mm) of the fungus S. sclerotiorum was placed in the center of the plate containing BDA (Potato-Dextrose and Agar) medium. For control, distilled water was used instead of the oil. The plates were kept in a B.O.D. type incubation chamber for 10 days at a temperature of 25 °C ± 1 °C and a 12 hour photoperiod, and mycelial growth was evaluated daily and at the end of the experiment the formation of sclerotia. The data measured were MCM, MIC (Mycelial Growth Index), IVCM (Mycelial Growth Rate Index), QEF (Number of Formed Sclerodes) and TME (Mean Sclerode Size). The experimental design was completely randomized, and the experimental unit was composed of a plate with five replicates. According to the results, the essential oil of pitanga presented better Average of Mycelial Growth (6.35 cm2), differing from the control (7.32 cm2) and goiaba oil (7.51 cm2). This statistical difference of the pitanga oil for the other treatments also occurred in the ICM, whereas for the IVCM, the three treatments did not differentiate each other. As for the production of sclerotia, the essential oil of pitanga did not allow the fungus to produce this structure of resistance, whereas the goiaba oil and the control presented an average of 16.6 and 15.8 sclerotia respectively. Goiaba oil presented larger sclerotia of the control. It was concluded that the essential oil of pitanga was the most efficient, since it did not allow the formation of sclerotia, thus controlling S. sclerotiorum in vitro.