Chemical Compositions, Phytochemical Screenings and Antifungal Activities of Cashew Nut Shell Liquid Extracts on Phytopathogenic Fungi of Yam (Dioscorea rotundata)

Abstract

This study was carried out to evaluate the antifungal activity of Cashew (Anacardium occidentale L.) nutshell liquid on fungal pathogens of dry rot diseases of yam (Dioscorea cayennensis subsp. rotundata). The Soxhlet extraction method was used and constituents were identified and quantified using Gas chromatography. Isolation and identification of fungi complexes associated with dry rot disease of yam were made using Potato dextrose agar (PDA) as a medium. The antifungal activity of CNSL was evaluated using the food poisoning technique on PDA at 25, 50, 75 and 100% concentrations of CNSL dissolved in dimethyl sulphoxide. Azulene (57.65%) was the major chemical component of CNSL with phenolic compounds; anacardol, cresols and anacardic acid, among other compounds. CNSL phytochemical screening showed the presence of flavonoids, alkaloids, saponins, tannins, phenols, terpenoids, volatile oil and steroids. Infected yam tubers were isolated, four fungal strains (Fusarium solani, Lasiodiplodia theobromae, Aspergillus fumigatus, and A. niger) were identified, and pathogenicity test confirmed the association of the fungi species with the dry rot disease of white yam. CNSL was active against the identified fungi and could potentially compete with conventional standard as a suitable fungicide against dry rot disease of white yam.