Abstract
Cultures of Pyricularia oryzae Cav. produce an extracellular phytotoxic glycopeptide capable of inciting white head symptoms quite similar to those of neck-rot blast at the concentration above 62.5ppm. After removing impurities with organic solvents, the toxin was purified from the culture filtrate by Sephadex G-100 column chromatography followed by Avicel® column chromatography. The purified toxin consisted of fifteen common amino acids with serine and threonine as major amino acids, and two hexoses, glucose and mannose. The estimated molecular weight was about 30, 000. The toxin was water soluble and heat-stable. Anatomical examination of rice stem treated with the toxin revealed obvious blockage of the vascular system due to an occlusion of the vessels, particularly in the nodes. The toxin showed no race specificity.
