Óleos essenciais com potenciais antifúngicos no controle da mancha-alvo causada por Corynespora cassiicola em tomateiro (Solanum lycopersicum)

Abstract

Tomato is one of the main horticultural crops worldwide due to its nutritional and economic importance. However, some phytosanitary problems limit the cultivation of this vegetable. In the northern region of the country, the target spot caused by the fungus Corynespora cassiicola is among the most important diseases that attack the aerial part of the tomato. The objective of this work was to evaluate the potential of essential oils of some species of the genera Lippia, Mentha and Ocimum, in the control of the target spot in tomato crop. Essential oil extraction, pathogenicity test, chemical analysis of oils, evaluation of the effect of oils on mycelial growth index, percentage of inhibition of sporulation, percentage of inhibition of germination and evaluation of disease severity in greenhouse were evaluated. The analyses of the results were performed with the aid of the SISVAR version 5.3 program. The values were submitted to variance analysis and the means compared by the Scott-Knott test, at 5% significance. Chemical analysis of essential oils revealed the major components for Lippia sidoides (thymol – 89.1%), Mentha arvensis (menthol – 89.8%), Mentha piperita (menthol – 38.3 %), and Ocimum gratissimum (1.8-cineol – 47.9%). In the in vitro assay, Lippia gracilis, L. sidoides and M. arvensis treatments had the lowest mycelial growth index and the highest percentage of sporulation inhibition. Regarding the percentage of germination inhibition, the highest value was obtained with the treatments Lippia gracilis, L. sidoides, M. arvensis and M. piperita. In the in vivo assay, the essential oils of L. gracilis and L. sidoides showed better performance in controlling the severity of the disease.