Morphological and Molecular Characterization of Pyricularia Oryzae Causing Blast Disease in Rice (Oryza Sativa) from North India

Rice blast is not only one of the earliest known plant disease but also one of the most widely distributed, occurring in every region of the world where rice is grown. Ten isolates of Pyricularia oryzae causing rice blast disease were evaluated for their morphological, pathogenic, virulence and genetic characterization using RAPD marker. Isolates were classified into three groups based on pathogenicity viz. severely pathogenic, moderately pathogenic and mildly pathogenic and also into four another gropus i.e. PG-I, PG-II, PG-III and PG-IV based on cultural & morphological characteristics. The molecular polymorphism among isolates by means were analyzed by means of RAPD-PCR and the genetic coefficient matrix derived from the scores of the RAPD profile showed that minimum and maximum per cent similarities among isolates were in the range of 80 to 35 percent respectively. The cluster analysis by unweighted pair group method with arithmetic average (UPGMA) separated the isolates into two major groups at 0.53 of similarity coefficient. Through morphological characterization, pathogenicity and RAPD grouping of isolates suggested no correlation among test isolates but genetic variability among P.oryzae isolates should be taken into account for the screening of blast resistant rice genotypes.