Genetic Differentiation of Rice and Non-rice Populations of Magnaporthe grisea from North-western Himalayas using Native Protein and Isozyme Polymorphisms

Native protein and isozyme markers were used to analyse the population structure of rice, finger millet (Eleusine coracana), jungle rice (Echinochloa colonum), goosegrass (Eleusine indica) and crabgrass (Digitaria sanguinalis) infecting isolates of Magnaporthe grisea from the north-western Himalayan region of India. Both protein and isozyme analyses revealed a high level of genetic diversity among different host-limited populations of the pathogen including those infecting rice. Cluster analysis of protein and isozyme data permitted the grouping of isolates in accordance with their host specificity. A close association was observed between specific esterase and shikimate dehydrogenase (SDH) isozyme electromorphs and the host specificity of the isolates, indicating that these electromorphs might be linked to the genes conditioning host specialization. Cluster analysis indicated the presence of two lineages in M. grisea species complex: first lineage with moderate bootstrap support was constituted by the isolates from rice, finger millet, goosegrass and jungle rice and a second statistically robust lineage was represented by the isolates from crabgrass. Subpopulations of the pathogen attacking rice and weeds in the same field were genetically distinct and the isolates from different hosts never exhibited a same multilocus haplotype. The overall results indicated that M. grisea populations infecting different hosts were genetically isolated and there was no gene flow among rice and non-rice isolates of the pathogen