ANTAGONISM BY SPECIES OF ALTERNARIA AND THE ISOLATION OF A CRYSTALLINE SUBSTANCE FROM THE FILTRATE OF CULTURES OF A. RADICINA

Abstract

Culture filtrates of five species of Alternaria were antagonistic to Phytophthora erythroseptica. Those of A. radicina exerted the greatest effect and they were followed in order of effectiveness by A. dianthicola, A. solani, A. brassicicola, and A. tenuis. The antagonistic principle in the filtrate of A. radicina was readily removed by activated carbon. By extracting this carbon with acetone, substantial yields were obtained of colorless, needlelike crystals, quite insoluble in water, but readily soluble in acetone, ethyl alcohol, ether, benzene, concentrated sulphuric acid, and 10% sodium hydroxide. The m.p. of the crystals, 204 °C. to 208 °C, and the deep pink color in solutions of sodium hydroxide distinguish the substance from alternaric acid. Water suspensions of the crystals were much less antagonistic to P. erythroseptica than the original filtrate and had little or no effect upon several species of bacteria.