In vitro antifungal activity of Myrcia ovata essential oils and their major compounds against pathogens of citrus, sweet potato, and coconut

Abstract

Myrcia ovata, an endemic species to the Brazilian Atlantic Forest, presents antifungal properties. The phytopathogens Colletotrichum acutatum, Plenodomus destruens, and Thielaviopsis paradoxa are responsible for the diseases citrus postbloom fruit drop, sweet potato foot rot, and coconut stem bleeding, respectively. The antifungal activity of the essential oils of five M. ovata chemotypes (MYRO-159, nerolic acid chemotype; MYRO-180, nerolic acid + linalool chemotype; MYRO-388, geraniol chemotype; MYRO-157, citral + (E)-nerolidol chemotype; and MYRO-174, isopulegol + linalool chemotype), four major compounds (nerolic acid, nerolic acid + linalool, geraniol, and citral + (E)-nerolidol), and three pure compounds (citral, (E)-nerolidol, and linalool) against the fungi C. acutatum, P. destruens, and T. paradoxa were evaluated. For this, in vitro tests were conducted in a completely randomized design with three replications, testing concentrations (v/v) ranging from 0.01 to 1.0 μL.mL^-1. All treatments presented toxicity at different levels to the three fungi. For C. acutatum, the essential oil from the individual MYRO-180 (nerolic acid + linalool chemotype) and its major compound showed the lowest Minimal Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) of 0.03 and 0.1 µL.mL^-1, respectively. For P. destruens, the essential oil from the individual MYRO-159 (nerolic acid chemotype) presented the lowest MIC of 0.05 μL.mL^-1. The nerolic acid + linalool chemotype and its major compound presented an MFC of 0.07 μL.mL^-1. For T. paradoxa, the major compound citral + (E)-nerolidol stood out with the lowest MIC and MFC of 0.03 and 0.2 µL.mL^-1, respectively. Linalool presented the lowest toxicity to the three tested fungi.