Abstract
Wheat root extract medium with dextrose supported production of fairly high concentration of the toxic principle by Helminthosporium sativum, the incitant of foot rot disease of wheat. When glucose was deleted from the medium, the fungus failed to grow. Synthetic media containing nitrate or asparagine as nitrogen sources with and without thiamine or biotin did not support toxin production. Autoclaving of the culture filtrate preadjusted to different pH levels resulted in greater loss of the toxin activity at the acid than at the alkaline range and least at the neutral level. Root tips of wheat seedlings exposed to lower dilutions of the culture filtrate were killed by the toxic principle.
