Abstract
Rice blast fungus, Pyricularia grisea, was isolated from blast lesions on paniclesof the rice multiline, 'Sasanishiki BL', in Miyagi Prefecture during 1996-2000. Sasanishiki BL consists of four isogenic lines, each of which possesses one resistance gene, Pik, Pik-m, Piz and Piz-t, respectively. Pathogenic races of the fungal isolates were identified as 003.0, 007.0 and 037.1. The former two races are incompatible with all the isogenic lines and are known to have existed in the prefecture for many years, whereas the latter 037.1 race is compatible with two of the isogenic lines, and has been rarely observed here until the introduction of Sasanishiki BL. Systematic samplings of fungal isolates from diseased Sasanishiki BL in certified seed production fields as well as from Sasanishiki BL produced from the seeds did not indicate that the compatible 037.1 race has been introduced via contamination of certified seeds.
