Isolation, identification, prove the pathogenicity and pathogenic variability of Fusarium oxysporum f. sp. lycopersici

Fusarium wilt, caused by Fusarium oxysporum f. sp. lycopersici (Fol), is a significant threat to tomato production worldwide. This study aimed to isolate, identify, and assess the pathogenicity and pathogenic variability of Fol isolates from the Jalna district of Maharashtra, India. Eight Fol isolates were collected from different tehsils and isolated using the tissue isolation technique on Potato Dextrose Agar (PDA) medium. Identification was based on morphological and cultural characteristics. Pathogenicity tests were conducted using sick soil and water agar methods on the susceptible tomato variety PKM-1. All isolates were confirmed pathogenic, satisfying Koch's postulates. Pathogenic variability was observed, with mortality rates ranging from 51.05% to 94.65% in the sick soil method. Five isolates (Fol-2, Fol-4, Fol-5, Fol-7, and Fol-8) were categorized as highly virulent, causing over 84% mortality. The water agar method resulted in 100% mortality for all isolates, with Fol-4 exhibiting the earliest symptoms. This study provides insights into the pathogenic diversity of Fol in the Jalna region, which may inform disease management strategies and breeding programs for Fusarium wilt resistance in tomatoes.