Antifungal Activity of Jatropha curcas Seed Extracts Analysed by GC-MS against Two Cowpea (Vigna unguiculata L.) Pathogenic Fungi

Abstract

Cowpea (Vigna unguiculata L. Walp.), native to Africa, is one of the most popular and widely grown seed legumes in arid and semi-arid areas. In these areas, fusarium wilt and white rots caused by Fusarium oxysporum Schl. f.sp. tracheiphilum and Sclerotinia sclerotiorum are the most devastating pathogens of cowpea crops, causing losses of 50-100 %, respectively. This study aims to evaluate the antifungal potential of biochemical compounds in Jatropha curcas L. seed extracts identified by GC-MS analysis against F. oxysporum and S. sclerotiorum. In vitro tests were carried out using aqueous, acetone and hexane extracts of J. curcas seeds at concentrations of 15, 30, 60 and 120 μL/mL and a synthetic fungicide (3.33 g/L). Mycelial growth and Minimal Inhibitory Concentrations (MIC50) were assessed. As a result, J. curcas seed extracts are rich in phytochemical molecules such as 9,12-octadecadienoic acid (Z,Z) ; n-Hexadecanoic acid ; Squalene ; D-Limonene ; 9,15-octadecadienoic acid, methy and 1,3-Dioxane, 5-ethyl-2,2-dimethyl, with antifungal activity. Total inhibition (100%) of mycelial growth of F. oxysporum and S. sclerotiorum was obtained in Petri dishes contaminated with the aqueous and acetone extracts at concentrations C3=60 µL/mL and C4=120 µL/mL, as well as with the synthetic fungicide. The MIC50 obtained with isolates of S. sclerotiorum and F. oxysporum were 9.2 and 9.96 µL/mL with the aqueous extract, respectively followed by the acetone extract (12.96 and 14.97 µL/mL). All Jatropha curcas lethal extracts tested were fungistatic, but the synthetic fungicide was fungicidal. Bioformulation based on J. curcas and characterization of pathogen are needed.