Abstract: The leaves of rice infected with rice blast disease were collectted from different rice cultivation areas. Pathogen isolation and purification culture were carried out by PDA medium, and the morphology of colony melanin and conidia were identified by preliminary screening. Mycelia DNA was extracted with kit, PCR amplification was performed using specific primers of Blast, and the amplified products were sequenced and Nucleotide Blast comparisons were performed. The results showed that the disease sample was taken six cultivation areas after the initial screening to determine 5 strains of secretion of melanin and observed its conidium, PCR product sequencing confirmed that the two sample sequence was the same, and the imperfect fungi of NCBI website door of grey pear spore （Pyricularia grisea） highly homologous, determine to obtain pure strains of rice blast.

Key words: rice blast, pathogen, isolation and purification, molecular identification