Comparative Assessment of Pathogenicity of Storage Rot Causing Fungi of Cocoyams (Colacasia Esculenta) (L.) Schott and their Host-Pathogen Interactions

Abstract

Pure isolates of five storage rot causing fungi of cocoyam (Colocasia esculenta) (L)Schott) corms were assessed for their potency in causing rot of the corms during storage. The isolates were Sclerotium rolfsii Sacc., Botryodiplodia theobromae Pat., Fusarium solanii (Mart) Sac., Fusarium SP. and Rhizopus stolonifer (Ehren ex. Fr) Lind. Each of the fungal organisms were inoculated on five corms of cocoyam free from blemish and were left for two weeks after which the extent of rot was determined by assessing both the area and volume of rot caused by each pathogenic fungus. S. rolfsii and B. theobromae proved most potent in causing rot with mean percentage volume of 14.50 cm3 and 10.14cm3 respectively. The area of rots caused by these two fungal organisms was again significantly higher (P.0.05) than the rest. The least pathogenic organism was R. stolonifer with only 3.10cm3 mean volume of rot caused and less than 2 cm2 mean area of rot. Fungal hyphae penetrated the corms of cocoyams from cell to cell both inter-and intra- cellularly in the carbohydrate rich storage parenchyma.

Key words: Comparative Assessment, Pathogenicity, Storage rot fungi, Cocoyam, host-pathogen interactions.