In vitro control of Fusarium oxysporum f. sp. lycopersici Race 3 by the innovative formulation consisting of a thymol-based emulsion, and evaluation of its effects on the vigor of tomato seeds

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is one of the major production constraints of tomato yield. The use of seed treatment is an alternative strategy to mitigate the occurrence of Fusarium wilt, induced by the Fol. Thus, the present study aimed to select the best condition for obtaining a thymol-based emulsion (Thy -E), considering surfactant concentration, vortex homogenization time (HVtx) and highintensity ultrasound (HUS) time, using both the visual/macroscopic and the microscopic approaches to evaluate Thy -Es. Thy -E prepared with 9.0 % ( w -1 ) surfactant, 2.5 min of HVtx and 3.0 min of HUS (Thy -E9 %S1) was achieved as the best condition to obtain a Thy -based emulsion, and was studied over time to evaluate the mean droplet diameter, hydrogen potential (pH) and electrical conductivity (EC) values. In addition, the effectiveness of Thy -E9 %S1 on Fol in terms of spores/conidial germination and mycelial growth, and its impact on vigor (germination, germination energy, germination index, hypocotyl, primary root growth, pH and EC tests) of tomato seed were assessed. Thy -E9 %S1 showed no evidence of considerable droplet destabilization or phase separation during 28 days of storage at 25 degrees C. The effective concentration values for 50 % (EC 50 ) and 90 % (EC 90 ) inhibition of Thy -E9 %S1 against Fol were 0.05 and 0.27 mg mL -1 thymol (Thy), respectively. No signs of phytotoxicity were observed in tomato seeds exposed to Thy -E9 %S1 at concentrations ranging from 2.5 to 10.0 mg mL -1 Thy, without affecting the vigor of tomato seeds for the concentrations used to control Fol. Thy -E9 %S1 showed stability over the time, fungicidal activity against Fol and did not affect the vigor of tomato seeds, enabling an alternative for the integrated plant disease management. These findings pointing out the Thy -E9 %S1 as an innovative delivery system to act as an antifungal for the seed industry.