Genotypic–phenotypic diversity and distinctiveness among Magnaporthe grisea isolates from rice and weed Echinochloa colonum

Abstract

AbstractRice blast disease caused by Magnaporthe grisea (Hebert) Barr is a serious biotic stress causing worldwide yield loss in cultivated rice. As high as 75% to 100% crop damage has been recorded in India. The disease is manifested by the appearance of lesions of various colours, size and spore liberation ability. The pathogen also infects 50 other hosts including weeds and grasses as secondary hosts. Information on genetic diversity, host specificity and phenotypic characters of the pathogens needs to be explored for better management of the disease. Therefore, fourteen M. grisea isolates from rice host and six isolates from weed host Echinochloa colonum were collected from three locations of coastal Odisha. Culture studies revealed that most isolates from virulent lesions had both black colour mycelia and pigmentation (B/B pattern). All the twenty M. grisea isolated produced bigger conidia with size ranged from 21.1–33.0µm to 7.6–12.7µm (length and breadth). Isolates from virulent lesions produced higher number of conidia. Isolates from weed had long and slender type conidia. Molecular genetic studies based on repetitive element Pot2 and random amplified polymorphic DNA (RAPD) could separate isolates on the basis of host plant and virulence of source lesion. Isolates from weed were consistently placed in separate group where presence and absence of bands specific to this group were observed. Rep‐PCR based on Pot2 amplified polymorphic DNA fragments where bands at 1750bp were specific to isolates from weed. Similarly, amplification specific to weed isolates was obtained at 1200bp by primer OPB10 in RAPD PCR. Amplification at these base pairs may be used for the development of markers to distinguish M. grisea from rice and weed. This is the first report of utilization of rep‐PCR and RAPD to distinguish M. grisea among rice and Echinochloa colonum in this region.