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Cultural and morphological characterization of pyricularia grisea causing blast disease of rice

Rice (Oryza sativa L.) is the world’s most important crop and a primary source of food for more than half of the global population. In India, rice is a staple food for more than 65 per cent population. However, the crop is subjected to attack by many diseases among which rice blast caused by the fungus Pyricularia oryzae is one of the most economically important diseases. The pathogen was isolated from the rice field of Uttar Banga Krishi Viswavidyalaya Farm, purified, and characterized based on morphological and cultural characters. Highest mycelial growth of 28.50 mm and 71.33 mm were observed in oat meal agar (OMA) medium at 2 and 6 days after inoculation (DAI) respectively, whereas growth of 47.77 mm was observed in potato dextrose agar (PDA) medium at 4 DAI. The mycelial growth was highest at 300C at 2 (27.00 mm) and 6 (72.17 mm) DAI whereas at 4 DAI, maximum growth of 43.50 mm was recorded at 250C. The best nitrogen and carbon sources for the pathogen in vitro were found to be potassium nitrate and glucose, respectively whereas the best pH for the growth of the pathogen was found to be 6. The conidia in infected leaf sample were three-celled with an average size of 22.42 × 8.59 μm. The conidia on rice grain were predominantly two celled with an average size of 16.45 × 7.46 μm. Conidial production was not observed in any of the media tested including PDA, OMA. However, on rice grain, the fungus produced conidia at 55-60 days. | Cultural and morphological characterization of pyricularia grisea causing blast disease of rice