Morphological Variability of Pyricularia grisea Isolates of Finger Millet Collected from Bengaluru (Karnataka) and Waghai (Gujarat) Regions of India

‘Blast’ caused by the heterothallic ascomycete, Magnaporthe grisea (Hebert) Barr. (Anamorph: Pyricularia grisea (Cooke) Sacc.) is the most important disease of finger millet. This study was conducted to collect, isolate, identify and characterize the pathogen using cultural and morphological characteristics. The cultural variability studies were carried out on twelve different culture media viz., Ragi yeast lactose agar (RYLA), Oat meal agar, Mathur's medium, Ragi leaf medium, Host extract+sucrose, Ragi meal medium, Peptone dextrose medium, Malt extract medium, Rose Bengal medium, Czapek's dox medium, Richard's medium and Potato dextrose agar. Studies on different solid media on the mycelial growth and sporulation of P. grisea showed that, maximum mycelial diameter (8.5cm) and abundant sporulation (>15) was observed in Ragi yeast lactose agar than other media. A total of 24 isolates were collected from different millet growing regions of India viz., Bengaluru and Waghai. Studies on morphological variability of different isolates showed considerable variations in colony colour and topography, conidia production and conidial size on RYLA. All the isolates produced grayish black to whitish black and whitish to buff colour with circular to irregular and slightly wavy colonies having course and smooth margins. Most of the isolates sporulated well on RYLA on 7–13 days. The conidia were pyriform (pear-shaped); either large, medium to small in size having rounded base and the pedicel narrowed towards the pointed tip. Variations in conidial size were also evident between the isolates and different locations. Size of the conidia (LxB) varied from 23.20×6.40 to 3.80×1.50 #m. Isolation and variability studies on finger millet blast pathogen helps to understand requirements for the growth and development of the pathogen and its sporulation which can be made use of in understanding variability of the blast pathogen.