<i>In vitro</i> and <i>in situ</i> Activity of <i>Cymbopogon citratus</i> Essential Oil Against <i>Alternaria alternata</i> and <i>Phomopsis carica-papayae</i>, Causal Agents of Papaya Leaf Diseases

Abstract

Papaya cultivation is considered to be one of the most important fruit-growing activities in Cameroon, and plays a vital role in improving the livelihoods of local producers. However, leaf diseases caused by devastating fungi are a real obstacle to the development of this crop. The aim of this study was to evaluate the antifungal potential of <i>Cymbopogon citratus</i> essential oil against <i>Alternaria alternata</i> and <i>Phomopsis carica-papayae</i>, fungal agents associated with the deterioration of papaya leaves in the Moungo region of Cameroon. The essential oil of fresh <i>C. citratus</i> leaves was extracted by hydrodistillation. Analysis of the chemical composition by GC then GC/MS revealed Geranial (45.24%), Neral (35.57%) and Myrcene (7.21%) as the majority compounds. <i>In vitro</i> antifungal tests on mycelial growth by incorporation into agar gave MICs of 900 ppm and 700 ppm against <i>A. alternata</i> and P<i>. carica-papayae </i>respectively. The MIC of 700 ppm proved fungicidal on <i>P. carica papayae</i>, while for <i>A. alternata</i> the fungicidal effect was obtained at a concentration of 900 ppm. <i>In situ</i>, the essential oil proved significantly active in inhibiting necrosis caused by the conidial complex of the two pathogens on papaya leaves, with a percentage inhibition of 85.93% at a concentration of 6000 ppm. <i>C. citratus</i> EO could therefore be used as an alternative to chemical fungicides in the fight against papaya leaf disease pathogens.