Manganese-oxidizing ability of isolates of the take-all fungus is correlated with virulence

Abstract

Two successive experiments described here show that the Mn-oxidizing ability of isolates of the take-all fungus Gaeumannomyces graminis var. tritici is positively correlated with the isolate virulence. Isolates of G. graminis var. tritici were screened for virulence on wheat in soil culture pot tests and visually scored for Mn-oxidizing capacity on agar plates. A comparison between experiments showed that the Mn-oxidizing ability of an isolate may be attenuated, as is virulence, with subculturing. Using a solution culture system, we calculated the rate of oxidation of Mn2+ by a virulent isolate, Ggt 500, as 4 nmol g-1 (dry weight hyphae) h-1. The significance of these results to the epidemiology of the take-all disease of wheat is discussed.