ASSESSMENT OF RICE BLAST INTENSITY AND MORPHOLOGICAL AND CULTURAL CHARACTERIZATION OF MAGNAPORTHE ORYZAE

Abstract

Rice (Oryza sativa) is the most important staple food for majority of human population worldwide. Rice blast disease caused by fungus Magnaporthe oryzae is one of the most important devastating disease which results complete failure of the crop under severe infection. Survey on rice blast was conducted in 12 farmer´s fields in three village of Bogura districts during Boro season 2020-2021. The incidence of rice blast in different locations varied from 3.01 to 59.92%. The highest incidence (59.92%) of blast disease was recorded from Bortola with a severity score 7 in BRRI dhan 58. The lowest incidence (3.01%) of blast disease was recorded from Bonani with a severity score 1 in BRRI dhan 28. Twenty four isolates were identified from collected neck blast sample for morphological and cultural characterization viz growth character, colony color, surface structure, shape and eleviation. The radial mycelial growth of 24 isolates were ranged from 40 to 60.67 mm at 4 DAI. The highest mycelial growth (60.66 mm) was observed in Mo22 with black color, smooth velvety surface texture, flat and regular shape at 4 DAI. On the other hand, the lowest mycelial growth was observed in Mo13 (40 mm) with brownish white color, rough cottony surface texture and regular shaped colony at 4 DAI. At 7 DAI, the highest mycelial growth (84.33 mm) was observed in Mo16 with brownish color, smooth velvety surface texture, regular, raised and good growth. On the other hand, the lowest mycelial growth (62 mm) was observed in Mo13 with whitish brown color, rough cottony surface texture, irregular shape, raised and good growth. OMA(Oat Meal Agar) found to be suitable for good growth and sporulation of all the isolates of Magnaporthe oryzae.