Antimicrobial Activity of Selected Indigenous Wild Flora in Kenya against Alternaria Pass/Florae Causing Brown Spot of Passion Fruit

Abstract

Antifungal activities of botanicals have been known since antiquity and used to extend shelf life of foods and treat human and animal diseases. Antifungal activity of heat stable extracts of six botanicals growing wildly in Kenya against Alternaria passiflorae the causal organism of brown spot of passion fruit were evaluated under laboratory condition (in vitro). Heating techniques mimicking the traditional methods were used in the extraction of active compounds. The extracts exhibited various activities against Alternaria passiflora colony growth and sporulation. Warbugia ugandensis, Rosemarinlls officinalis and Urtica massaica were more toxic to Alternaria passiflora than Aloe volkensii, finger euphobia and solanam nigrum which were not significantly different from each other. Solanum nigrum was however relatively more effective in inhibiting sporulation followed by Rosemarinus officinalis and Warbugia ugandensis. Further tests on W. lIgandensis, R. officinalis and S. nigrum using different quantities of the botanicals indicated that the effects were concentration dependent. The fungitoxicity however decreased fast with incubation period. Concentrations >40 g of botanical materials/50 ml of PDA media were more toxic to the fungus. There is need for further studies to identify the active ingredients and best extraction methods as heat is known to destroy some compounds.