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In vitro activity of essential oil of Ocimum selloi and its major chemical compound against Moniliophthora perniciosa, causal agent of witches’ broom disease in cacao

Costa, L. C. B., Costa, J. C. B., Pinto, J. E. B. P., Bertolucci, S. K. V., Alves, P. B., Nicolau, E. S.
Acta horticulturae 2016 no.1125 pp. 137-144
Alternaria alternata, Glomerella cingulata, Moniliophthora perniciosa, Ocimum selloi, antifungal agents, antifungal properties, beta-caryophyllene, dose response, essential oils, fungi, gas chromatography-mass spectrometry, methyl chavicol, methyl eugenol, minimum inhibitory concentration, mycelium, oils, plant pathogens, spathulenol, spore germination
The efficacy of Ocimum selloi essential oil was evaluated for controlling the growth of mycelia and spore germination of phytopathogens. Six compounds (99.89%) of the total oil were identified by GC-MS, methyl chavicol, methyl eugenol, β-caryophyllene, germacrene-D, bicyclogermacrene and spathulenol. Essential oil was tested for anti-fungal activity against Moniliophtora perniciosa, Colletotrichum gloeosporioides and Alternaria alternate, which was determined by disc diffusion and minimum inhibitory concentration (MIC) determination methods. Application of the oil reduced mycelial growth in all three fungi in a dose dependent manner, with maximum inhibition being observed at a concentration of 1000 ppm. Such antifungal activity could be attributed to methyl chavicol since the pure compound was shown to be similarly effective against M. perniciosa at 1000 ppm. The oil, when applied at a concentration of 1000 ppm, reduced the spore germination of C. gloeosporioides and M. perniciosa by 93 and 87%, respectively, but had no effect on the A. alternata. It is concluded that the oil from O. selloi and its major constituent, methyl chavicol, are efficient in inhibiting M. perniciosa, but less effective against C. gloeosporioides and A. alternata. The results obtained from this work may contribute to the development of alternative anti-fungal agents to protect the cacao crop from fungal disease.