JAZET DONGMO PIERRE MICHEL*;
Tchinda S.E., Ambata A.H.T., Davy M.V., Bidja M.J.P., Kenfack N.S.B;
Kabeyene M.O.*, Tchinda S.E., Ambata A.H.T., Davy M.V., Bidja M.J.P., Kenfack N.S.B., Sameza M.L. and Jazet D.P.M.
Laboratory of Biochemistry, Department of Biochemistry, Faculty of Sciences, University of Douala, Cameroon,
P. O. Box 24 157 Douala, Cameroon.
*Corresponding : E-mail : mjazet@yahoo.com Tel: +(237) 699440618/ 674859412
INTRODUCTION
In Cameroon, the cocoa sector faces several constraints, notably black rot caused by fungi of the genus Lasiodiplodia. The use of synthetic fungicides, although effective, is expensive and polluting. Hence the orientation towards natural substances to alleviate this problem. It is in this perspective that this work was carried out with the objective of evaluating the antifungal activity of essential oils and formulations of the flower buds and leaves of Syzygium aromaticum on the fungus Lasiodiplodia pseudotheobromae, the causal agent of black rot of cocoa.
METHODOLOGY
The pathogen was isolated from infected pods and identified by macroscopic and microscopic observations. The essential oils were extracted by hydrodistillation using Clevenger-type equipment and their chemical composition analysed by GC/MS. The microemulsions (ME) were prepared cold under mechanical stirring with Tween 80, Glycerol and Monopropylene glycol as surfactants. The antifungal activity of the essential oils and their formulations was evaluated in vitro on mycelial growth by the agar incorporation method.
RESULTS
Based on the pathogenicity test, the ability of the isolated pathogen to induce disease and macroscopic and microscopic observations, identified it as Lasiodiplodia pseudotheobromae. Extraction yields were 10.3% for flower buds and 0.93% for leaves. The analysis of the chemical composition revealed Eugenol (87.08% and 90.54%) and Caryophyllene (6.40% and 8.43%) as the major compounds for the flower buds and leaves of S. aromaticum respectively. The microemulsions obtained were found to be stable, whitish in colour, homogeneous with mean particle sizes of 116.937 and 110.763μm. The in vitro antifungal activity on mycelial growth revealed significant inhibition for the essential oils and microemulsions at MICs of 750ppm and 650ppm respectively.
IMPACT OF RESULTS
The different essential oils and microemulsions of S. aromaticum could be potential alternatives in the phytoprotection of cocoa.
Keywords : Essential oil, microemulsions, black rot, antifungal potential, plant protection.
