Pathogenicity assessment of five Fusarium Species from onion (Allium cepa L.) on four tomato (Solanum lycopersicum L.) varieties in Burkina Faso

Abstract

Fusarium species are among the most destructive plant pathogens, causing significant yield losses in many crops, including tomato. Their wide host range raises concerns about cross-pathogenicity between crops commonly grown in market gardening systems, such as onion and tomato. The present study evaluated the pathogenicity and aggressiveness of Fusarium strains isolated from onion on four tomato varieties (UC82B, Cobra 34 F1, Mongal F1, and Petomech) under controlled conditions. Disease incidence (DI) was assessed at 21, 28, and 35 days after inoculation (DAI). Results demonstrated significant variation in aggressiveness among the tested species. Fusarium oxysporum was the most virulent, reaching 85 ± 10% DI in UC82B at 35 DAI. F. proliferatum and F. falciforme also induced severe infections, with DI of 78.33 ± 16.67% in Cobra 34 F1 and 70.83 ± 5% in Petomech, respectively. F. solani and F. acutatum were comparatively less aggressive but still caused substantial disease in certain varieties. Varietal responses revealed that UC82B was the most susceptible, recording DI values exceeding 80% for multiple species, while Mongal F1 and Cobra 26 F1 exhibited moderate resistance, and Petomech showed intermediate susceptibility. Control treatments remained symptom-free, confirming Fusarium as the causal agent. Re-isolation and morphological characterization of the fungi fulfilled Koch’s postulates, confirming the identity of F. acutatum, F. solani, F. proliferatum, F. oxysporum, and F. falciforme. These findings demonstrate strong cross-pathogenicity of onion-derived Fusarium strains on tomato, highlighting the importance of resistant cultivars and integrated management strategies to limit disease spread in intensive vegetable cropping systems.