Abstract:
Rice blast, caused by Magnaporthe oryzae, is one of
the most devastating diseases of rice worldwide,
particularly in South and Southeast Asia. This study
aimed to assess the incidence of rice blast in two major
rice-growing districts, Cumilla and Brahmanbaria, of
Bangladesh, and to evaluate the morphological
variation of the causal pathogen under different culture
media. Field surveys were conducted during the Boro
season 2020-2021, and disease severity was recorded
using standard disease scoring scales. Infected samples
were collected and used to isolate M. oryzae in the
laboratory. A total of 6 isolates of M. oryzae were
cultured on Potato Dextrose Agar (PDA), Oatmeal
Agar (OMA), Potato Sucrose Agar (PSA), Rice Flour
Yeast Agar (RFYA), and their morphological features
were compared. Significant differences in colony color,
surface texture, growth rate, and conidial shape were
observed among the media. The highest mycelial
growth was recorded on RFYA media, which is 90 mm
with grayish white colony color and a rough, cottony,
irregular surface structure. At the same time, distinct
pigmentation was prominent on OMA and other media.
These findings enhance understanding of rice blast
distribution in Bangladesh and the media-dependent
morphological traits of M. oryzae, which can aid in
future diagnostics and disease management strategies.
