Int.J.Curr.Microbiol.App.Sci (2018) 7(6): 3808-3812 3808 Original Research Article https://doi.org/10.20546/ijcmas.2018.706.447 Identification of Physiologic Race(s) of Magnaporthe grisea (Herbert) Barr Causing Blast Disease of Rice Prevailing in Different Agro-Climatic Zones of Assam, India K. D. Singha* and D. Hazarika Regional Agricultural Research Station, Assam agricultural University, Shillongani-782 002, India *Corresponding author ABSTRACT Introduction Rice is the main staple food in India. It is cultivated throughout India and more particularly in Assam. But most of time its production become limited due to attack by many diseases. One of the most destructive and wide spread fungal diseases of rice (Oryza sativa L.) is blast caused by Magnaporthe grisea (Herbert) Barr (anamorph Pyricularia grisea Cav.) also affect other host grasses. However, reports on the specific range of blast fungus hosts are contradictory. This discrepancy could be attributed to the variation of genetic back-ground of the fungus. The variation of genetic back ground leads to variation in pathogenicity, increase difficulties in developing resistant varieties suitable for different agro climatic conditions. Padmanabhan et al., (1970) also reported existence of great variability of pathogenicity among the Pyricularia oryzae isolates further similar result was also reported by Ou (1985). Padmanabhan et al., 1970, Veeraraghavan and Premalatha Dath 1975, 1976 and 1977 were reported existence of different physiologic races of Magnaporthe grisea time to time. The prevalence of physiologic race of P. oryzae ‘IE 3’ in Assam was reported by Roy (1987). Considering the long gap of work in this aspect particularly, to determine the number and distribution of physiologic races of International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 7 Number 06 (2018) Journal homepage: http://www.ijcmas.com Blast is one of the most destructive and wide spread disease of rice. It is caused by Magnaporthe grisea (Herbert) Barr in different stages of its growth period. Of the 16 number of isolates collected from different locations of Assam, 6 physiologic races viz., IB8, IB33, IC17, ID1, ID10 and IF1 are found prevailing in this region. The isolate belongs to international race groups IB has not been detected so far in India. Under the race group IB, two new races were identified IB8 and IB33. Besides, in international race group ID and IF new race ID 10 and IF 1 respectively were also identified. Keywords Blast, rice, Magnaporthe grisea, physiologic race, isolate Accepted: 25 May 2018 Available Online: 10 June 2018 Article Info