Survey on Rice Blast and Morphological Characterization of Magnaporthe oryzae oryzae

Aims: To survey and study morphological characterization of rice blast caused by Magnaporthe oryzae oryzae (MoO) that has become a major factor limiting rice yield throughout the world. Study Design: Complete Randomized Design (CRD). Place and Duration of Study: Mycology Laboratory, Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka from June 2018 to December 2019. Methodology: A survey was done in three northern districts of Bangladesh namely Gaibandha (Gobindogonj and Mohimagonj), Dinajpur (Birampur) and Bogura (Dupchanchia), disease incidence and severity was recorded and samples were collected. Five different media including Water Agar (WA), Potato Dextrose Agar (PDA), Potato Sucrose Agar (PSA), Rice flour Yeast Agar (RfYA) and Oat Meal Agar (OMA) were used to culture MoO. Colony characters like growth character, color, surface structure and shape of 28 MoO isolates were recorded in PDA. Results: Among the three surveyed districts, the highest incidence (84.26%) of blast was recorded from Gobindogonj with a severity score of 7. The highest severity score 9.00 (65%) of blast was recorded in Mohimagonj where blast incidence was only 29.12%. Among the five different growth media highest mycelia growth was observed in Oat Meal Agar (20 mm) and lowest in Water Agar (10mm) at 7 DAI. Colony color of all the isolates was whitish grey to blackish with sufficient growth and the average colony diameter was 50 mm. Conclusion: The results of the present study demonstrate that there is a certain level of morphological diversity such as mycelial growth rate and colony characters like color, surface structure and shape exists among isolates of MoO.