Recently some attempts have been made to use antibiotics for agricultural use, and several kinds of agricultural antibiotics have already been found. Some of the most improtant agricultural antibiotics in Japan are those against Piricularia oryzae of rice plant, and antipiriculin (antimycin A)¹⁾, blastmycin²⁾, antiblastin³⁾, blasticidins A, B, C⁴⁾ and S⁵⁾ have been reported hitherto. In the authors’ laboratory, antibiotics active on Piricularia oryzae, in vitro and in vivo, have been searched, and blasticidin S has been found to be the most promising anti-blast agent.

Since blasticidin S-producing organisms have been isolated wide from various soil samples, this paper deals with taxonomic studies on five strains of blasticidin S-producing organisms which have been isolated so far in our laboratory.