Abstract

Fusarium wilt can cause severe losses in many vegetables and flowers, field crops and plantation crops. The main method for controlling Fusarium wilt is through chemical methods which have the disadvantage of polluting the environment and are expensive. Thus, there is a need for more environmentally friendly and cheaper techniques for controlling Fusarium Wilt. This study screened the phytochemical compounds of two plant extracts; Tithonia diversifolia and Kigelia africana and assessed their potency in controlling plant fungal pathogen F. oxysporum, which causes fusarium wilt in tomatoes. The phytochemical analysis revealed that the two plant extracts contained saponins, tannins, terpenoids, flavonoids, glycosides and phenolics except alkaloids and steroids which were only found in T. diversifolia. The mean inhibitory zones ranged from 7.93 to 10.44 mm for T. diversifolia at 25 to 100 g/l. The mean inhibitory zones for K. Africana ranged from 12.07 to 15.56 mm at 25 to 100 g/l. K. Africana extracts had the highest inhibitory (antimicrobial) activity. Combining both extracts was more effective compared to the single extract. The effect of the combined plant extract and positive control was statistically significant (p < 0.05). This study provides scientific evidence that K. africana and T. diversifolia extract possess antifungal activity and can be used as a broad-spectrum in managing microbial diseases.

Key words: Plant extracts, phytochemical screening, antimicrobial and antifungal properties, Fusarium oxysporum.