SURVEY ON WHEAT BLAST AND MORPHOLOGICAL VARIABILITY OF MAGNAPORTHE ORYZAE TRITICUM

Abstract

Wheat blast caused by Magnaporthe oryzae triticum is a serious disease of wheat causing high yield losses which has become a critical problem for wheat production in Bangladesh. A survey was conducted in eight sites (village) of four upazila under two districts of southwestern region of Bangladesh during November 2017 to March 2018. A total of 500 bleached spike samples were collected. Disease incidence and severity varied among collection sites. The highest disease incidence (43.00%) was recorded in Chithlia of Mirpur and the lowest disese incidence (15.00%) was recorded in Bollobpur of Mujibnagar. The highest disease severity (20.00%) was recorded in Dhanakkhula of Gangni and the lowest disease severity (10.00%) was recorded in Chithlia and Amla of Mirpur, Bollobpur and Doriapur of Mujibnagar. Diseased and bleached spikes were collected, dried and kept in brown paper envelope and maintained in 4 o C temperature for the study. Magnaporthe oryzae triticum isolates were isolated on Potato dextrose agar and Oat meal agar media and identified based on 3 celled pyriform conidia and cultural and microscopic characteristics. Eight isolates has been isolated from eight sites and cultured on Potato dextrose agar and Oat meal agar. Cultural characteristics of eight isolates differed among the collection sites. Mycelial growth rate/day of eight isolates ranged from 2.17 mm to 3.58 mm on PDA and 1.70 mm to 5.99 mm on OMA. Collected Isolates varied based on their sporulation from poor to excellent in microscopic field. Sporulation of Magnaporthe oryzae triticum isolates on PDA media is rare.