This research investigates the pathogenic variability of Pythium aphanidermatum and its impact on tobacco (Nicotiana tabacum L.) cultivation, specifically bidi tobacco, a major cash crop of Gujarat, India. Key findings include the isolation and identification of 15 pathogenic isolates from infected soil, with Pa4 and Pa14 isolates showing the highest virulence, causing up to 98% seedling mortality. Screening across 28 wild Nicotiana species and tobacco varieties revealed varying resistance, with ABT 10 and Anand 2 being relatively more resilient, while no variety was entirely resistant....