Abstract

Fusarium wilt is among the most destructive diseases limiting tomato production worldwide. Accurate pathogenicity assessment is essential for understanding host–pathogen interactions and developing effective disease management strategies. This study investigated the influence of different inoculation methods on the pathogenicity of Fusarium isolates infecting two susceptible tomato varieties. Wilted tomato plants were collected from major tomato-producing areas in Northern Nigeria, namely Bomo and Kwarin Bala (Kaduna State), Kadawa (Kano State), and Danja (Katsina State). Fungal isolates obtained from diseased vascular tissues were identified using morphological characteristics and molecular sequencing. Three Fusarium isolates were selected for pathogenicity evaluation using soil inoculation, leaf smear, and foliar spraying methods on tomato varieties NHT332 and NHT18 under screen house conditions. Disease severity was assessed fourteen days after inoculation using a five-point rating scale. Significant differences (P < 0.05) were observed among inoculation methods, Fusarium isolates, and tomato varieties. Soil inoculation resulted in the highest disease severity (3.33), followed by leaf smear (3.00), whereas foliar spraying recorded the lowest severity (1.33). The Danja isolate (FUSDJ) exhibited the greatest virulence, while the Kwarin Bala isolate (FUSKB) was the least virulent. Variety NHT332 showed significantly greater susceptibility than NHT18. Significant interactions among isolate source, inoculation method, and tomato variety were also observed. The findings indicate that soil inoculation most effectively reproduces Fusarium wilt symptoms and represents the most suitable method for pathogenicity studies involving tomato and Fusarium species.