VARIATION IN MAGNAPORTHE ORYZAE AND SCREENING RICE GERMPLASMS AGAINST RICE BLAST

Abstract

ABSTRACT Rice (Oryza sativa L.) is one of the most important crops and over half of the world’s population consumes it as the staple energy source. Rice blast pathogen is widely distributed and highly destructive under favorable conditions caused by the fungus Magnaporthe oryzae, affecting global rice production. The blast pathogen affects different parts of a rice plant during pathogenesis. One of the serious forms of rice blast is neck blast but the leaf blast is well studied and the screening method for the same is precisely standardized. Blast resistance, tended to be unreliable with resistance often failing, or broken down, under field conditions, therefore there is always continuous search for resistant donors/lines. In Boro season 2020-2021, a survey on rice blast has been carried out in different locations of Cumilla and Brahmanbaria districts of Bangladesh. Blast incidence and severity ranged from 0 to 9 scale and 0% to 57%, respectively. A total of 6 isolates of Magnaprothe oryzae was isolated, identified and their cultural characterization was done. Radial mycelial growth of all isolates ranged from 7 mm to 72 mm in PDA, 10 mm to 66 mm in OMA and 10 mm to 90 mm in RfYA and 7.5 mm to 48.5 mm in PSA. A total of 18 rice germplasms were screened at UBN, BRRI, Gazipur in Robi season of 2020 to 2021 to determine the source of resistance in rice germplasm against Magnaporthe oryzae. Germplasms screening was done by following 0-9 Standard Evaluation Scale (SES) for leaf blast. Among 18 rice lines, only BRRI dhan32, BRRI dhan33 and BINA17 were shown resistance against rice blast under nursery condition upon artificial inoculation. These three varieties i.e. BRRI dhan32, BRRI dhan33 and BINA17 could be used for breeding purpose to develop high yielding blast resistant rice variety.