Importance of the early blight disease <p>Tomato is a globally important vegetable crop that faces numerous pathogenic threats throughout its growth period. Among these, early blight caused by <i>Alternaria solani</i> is a destructive disease that leads to significant losses for tomato growers across different seasons.</p> Aim of the study <p>This study aims to understand the variation within the <i>A. solani</i> infecting tomato plants.</p> Method <p>The fungus was characterized through phenomorphology and PCR identification utilizing markers such as ITS, SSU, LSU, and β-tubulin and genetic variation identified through Restriction Fragment Length Polymorphism (RFLP).</p> Results <p>Roving survey indicated that during the vegetative stage, early blight severity ranged from 1.03 to 16.22%, while during the fruiting stage, it ranged from 16.11 to 52.89%. Furthermore, 23 isolates of <i>A. solani</i> were collected and identified from five districts in Karnataka, India. These isolates were identified based on micro-morphological evaluations, cultural characteristic assessments, and a multilocus gene analysis comprising four segments (ITS, SSU, LSU, and β-tubulin). The genetic variation among the isolates was investigated using RFLP analysis revealed polymorphism within the four segments (ITS, SSU, LSU, and β-tubulin) of the 23 <i>Alternaria</i> isolates.</p> Conclusion <p>This study aims to investigate the genetic and pathogenic variability of <i>Alternaria solani</i>, the causal agent of early blight in tomatoes. By analyzing isolates collected from different regions and seasons and seeks to identify variations in virulence, genetic makeup, and fungicide resistance. These insights are crucial for developing effective disease management strategies and breeding resistant tomato varieties, thereby contributing to the sustainable control of this important pathogen.</p>