- 1School
of Biological Sciences, University of Nairobi, P.O. Box 30197-00100,
Nairobi, Kenya; Department of Biology, Faculty of Science, Mwenge
Catholic University, P.O. Box 1226, Moshi, Tanzania.
- 2School of Biological Sciences, University of Nairobi, P.O. Box 30197-00100, Nairobi, Kenya.
- 3Department
of Biological Sciences, School of Science and Information Sciences,
Maasai Mara University, P.O. Box 861-20500, Narok, Kenya.
Abstract
The objective of this study was to determine the chemical composition and antibacterial activity of essential oils (EOs) of Tagetes minuta against three phytopathogenic bacteria Pseudomonas savastanoi pv. phaseolicola, Xanthomonas axonopodis pv. phaseoli, and Xanthomonas axonopodis pv. manihotis. The essential oils were extracted using steam distillation method in a modified Clevenger-type apparatus while antibacterial activity
of the EOs was evaluated by disc diffusion method. Gas chromatography
coupled to mass spectrometry (GC/MS) was used for analysis of the chemical
profile of the EOs. Twenty compounds corresponding to 96% of the total
essential oils were identified with 70% and 30% of the identified
components being monoterpenes and sesquiterpenes, respectively. The
essential oils of T. minuta revealed promising antibacterial activities against the test pathogens with Pseudomonas savastanoi pv. phaseolicola
being the most susceptible with mean inhibition zone diameters of 41.83
and 44.83 mm after 24 and 48 hours, respectively. The minimum
inhibitory concentrations and minimum bactericidal concentrations of the
EOs on the test bacteria were in the ranges of 24-48 mg/mL and
95-190 mg/mL, respectively. These findings provide a scientific basis
for the use of T. minuta essential oils as a botanical pesticide for management of phytopathogenic bacteria.
