Methods of estimation of the pathogenicity of the fungus Phoma exigua var. exigua

Abstract

During the period 1977-1981 33 isolates of Phoma exigua were recovered from diseased leaves, stems, root crowns and seeds of soybean cultivated in different localities of Poland. None of the obtained isolates caused disease symptoms on soybean and other plant species when they were inoculated by spraying with conidial suspension. Infection developed only on wounded plants after inoculation. Phoma exigua occurring on soybean in Poland is not a specialized pathogen of this plant, but a plurivorous weak or waund parasite which attacks all kinds of plants and so is P. exigua var. exigua. Among seven of the applied inoculation methods the best one seems to be the laboratory one, in Petri plates, with culture discs exposed on the seedling hypocotyl. Other methods varied in precision and were more time-consuming.