Background:

Natural products have a high potential to replace synthetic fungicides, however, these compounds vary depending on the growth stage of the plant and climatic conditions of collection, as well as the mixture of compounds present in the plant material. The separation of these active principles and the evaluation of their efficacy on various phytopathogenic fungi, could increase their use under a biorational scheme and according to the principles of green chemistry.

Objective:

To evaluate in vitro the effect of the active ingredients of botanical origin (PAB): 1-8 cineol (Eucaliptol), β-citronelol, D-limonene and allyl isothiocyanate, on the mycelial growth of the fungi Alternaria solani, Fusarium oxysporum and Rhizoctonia solani.

Methods:

The inhibitory concentration (IC50) of the PAB was determined for each species of phytopathogen, by means of bioassays in a poisoned PDA culture medium. Cultures were prepared with eight concentrations plus one control for each compound: 20-160 ppm for β-citronelol, 500-4000 ppm for allyl isothiocyanate and 1000-4500 ppm for eucalyptol and D-limonene, with intervals of 20 and 500 ppm. Daily mycelial growth readings were taken until the petri dish cover (Ø 9 cm). Maximum likelihood estimation of the multivariate probit regression model was applied to the results for the determination of the IC50s and their fiducial limits.

Results and conclusion:

β-citronellol presented the lowest IC50, followed by allyl isotocyanate, D-limonene and eucalyptol. The IC50s of β-citronellol were 5.44, 6.25 and 6.89 ppm for F. oxysporum, R. solani and A. solani respectively. According to the results obtained, the use of these PABs is recommended for the control of the phytopathogens studied.

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