Important pathogenic fungi such as Fusarium species are mostly associated with the wilting of tomato plant leaves and constitute a serious limiting factor for tomato production. Therefore, this study aimed to screen tomato varieties commonly cultivated in Nigeria to determine their host resistance status to Fusarium oxysporum. The treatments included Trichoderma asperellum, Trichoderma harzianum, and Mancozeb fungicide. Data recorded included the incidence and severity of the pathogen, plant height, leaf number, and fruit yield of the tomato plants. Tomato plants grown with Trichoderma sp. exhibited better performance in terms of average fruit yield with 6.5 for Trichoderma asperellum and 6.7 for Trichoderma harzianum compared to the average yield of 1.7 fruit for Mancozeb fungicide. The lowest disease incidence was recorded in the Variety Three plants (NGB00737) with a 5.81% incidence in the Mancozeb-treated plants. Conversely, Trichoderma asperellum-treated plants in Variety Three (NGB00737) had the highest disease incidence of 46.49%. In Variety Four (NGB00695), plants treated with Mancozeb had the least disease variety with a severity rating of 1. Similarly, Variety Five (NGB00725) plants treated with T. asperellum showed the least disease severity rating of 1. All other treated plants showed higher severity values of 4. The Trichoderma species also improved the fruit yield and some agronomic parameters of the tomato plants compared to the chemical control. Local farmers are therefore encouraged to further exploit the potential of Trichoderma species as means of control for fungus-based diseases in tomato plants such as those caused by Fusarium.

Keywords: Tomato, Fusarium, Trichoderma, antagonism, biological control, fungicide