ANTIMICROBIAL ACTIVITIES OF Tithonia diversifolia AND Kigelia africana AGAINST Fusarium oxysporum IN TOMATOES

Abstract

Fusarium wilt disease caused by the soil-borne fungus Fusarium oxysporum Schlechtthe is a serious threat to tomato production worldwide. Chemical and cultural methods of management used are either ineffective or toxic to the environment. Plant secondary metabolites; therefore, pose a possible alternative because they are environmentally friendly and have minimal effect on non-target organisms. This study screened phytochemical compounds of two plants; Tithonia diversifolia and Kigelia africana and assessed their potency in controlling plant fungal pathogen F. oxysporum, the causative agent of Fusarium wilt disease in tomatoes. Leaf extracts of T. diversifolia and fruit extract of K. africana were used in this study becauses they are readly available and the plnts have been used in the treatment of varius diseases in humanbeings. The plant etract were concentrated in water and screened for phytochemical contents using standard procedures. Concentrations used were 25 g/L, 50 g/L and 100 g/L to sock the disc. Fusarium oxysporum was isolated from infected soil using potato dextrose agar media while the antifungal activity was evaluated by measuring the zone of inhibition against the test organism. In determining the antimicrobial properties of each of the plant extract, a 3×3 randomised complete block design was used, replication was done 3 times. The results showed that the mean inhibitory zones were highest at 100g/l in both plants, although K. africana fruit extract portrayed the higher inhibitory activity compared to Tithonia africana. The effect of the plant extracts and the positive control were statistically significant (pα0.05). This study indicates that K. africana and T. diversifolia possess the antifungal activity and can be used as a broad-spectrum fungicide against F. oxysporum. The effect of the plant extract was statistically significant (p<0.05). The Mean of inhibition ranged from 23.67 to 7.78 mm for Tithonia diversifolia and 23.67 to 11.75 for Kigelia africana. While for the combined extract the The Mean of inhibition ranged from 22.78 to 7.93 . The minimum reduction in sporulation was recorded in the positive control, which was significantly lower than the rest of the treatments.These plant extracts may provide an effective measure for the management of Fusarium wilt of tomatoes that may form an integral part of integrated pest management and become a prospect alternative to conventional fungicides.