Fusarium Disease of Gladiolus

its Causal Agent

Abstract

Three forms of the Fusarium disease of Gladiolus, known as the vascular, brown rot, and basal dry rot forms, have been described by other workers. The agent or agents which cause these disease forms have been assigned various specific names, with the result that the exact relation of the different symptom types and their causal agent or agents has been in a state of confusion.  The purpose of this investigation was to rectify the confusion by determining if strains of Fusariutn producing different symptoms could be fitted into weell-defined groups on the basis of their pathogenicity and physiological characters.  From several hundred isolates of Fusarium that had been cultured from diseased gladiolus corms, 40 isolates were selected for comparison in pathogenicity tests and physiological  studies. Comparisons of isolates from the three disease forms were made by means of their reactions to temperature, reactions to aniline dyes, reactions to copper salts, reactions to mercuric chloride, color reactions on steamed rice, growth types on differential media, pH changes produced in liquid media, spore measurements, and tendency to reproduce the same or different disease forms in inoculated plants and corms.  The isolates varied a great deal in their
reactions in these tests, but no definite pattern for association of variables could be determined; the variations seemed to occur independently. The isolates did not fall into well-defined groups; the isolates from the three disease forms could not be distinguished by any of the tests used. The pathogenicity tests showed that a single isolate is capable of producing more than one form of the disease.  The evidence obtained in these studies shows that strains of the gladiolus Fusarium are extremely variable and that some of them apparently are quite unstable.  It is proposed that all forms of the gladiolus Fusarium be included under the name Fusarium oxysporum f. gladioli (Massey) Snyder & Hansen.