Vol. 9, Special Issue 9, Part S (2025)

Tomato (Solanum lycopersicum L.) is an economically important vegetable crop of tropical and subtropical countries, which is grown in almost all the states of India. Its cultivation is affected by many diseases, among which early blight disease caused by Alternaria solani is the major one. Considering the importance of crop and the losses caused by the pathogen, investigations have been conducted on cultural, morphological and molecular characterization of the pathogen. Among the eight different culture media tested for the growth of Alternaria solani, potato dextrose agar medium recorded the maximum radial growth of 90.00 mm in all four isolates, followed by oat meal agar (85.18 to 90.00 mm). While, the least radial growth was recorded in yeast extract agar (19.32 to 22.06 mm). Colony growth was found to be flat or fluffy with regular to irregular margins and light to dark gray pigmentation. Conidia produced by all the four isolates in PDA medium were pale to olivaceous brown in colour, oblong to muriform in nature with size ranging from 81.47 to 95.61 µm in length and 14.21 to 18.85 µm in width, containing 5-9 transverse and 2-3 longitudinal septa. Molecular characterization of four pathogen isolates were done through the CTAB DNA extraction method, followed by PCR amplification using universal primers ITS1 and ITS4. PCR amplification yielded bands at 550 bp in all four isolates. Sequencing and BLAST analysis demonstrated over 98 per cent sequence similarity to Alternaria solani. This confirms that the four isolated pathogens are Alternaria solani. Corresponding accession numbers were obtained by depositing the sequences of all four isolates in NCBI GenBank. This comprehensive molecular and morphological characterization underscores the precise identification of the pathogen causing early blight disease of tomato.