Do collembola affect the competitive relationships among soil-borne plant pathogenic fungi?

The feeding preference of the collembolan Protaphorura armata in the presence of Fusarium culmorum and Gaeumannomyces graminis var. tritici, two soil-borne fungi pathogenic for winter cereals, was studied in a simplified experimental system including wheat seedlings. Analysis of gut content of all animals from microcosms containing inoculum of both fungi showed that F. culmorum was clearly preferred but that G. graminis var. tritici was also fed. At microscopic examination the majority of F. culmorum conidia present in the gut lacked cytoplasmic content, and only few conidial cells were intact. The feeding preference of P. armata favoured G. graminis var. tritici over F. culmorum in the competition for infection sites on wheat plants; in fact, the former resulted the prevalent cause of plant disease. The viability of fungal propagules after passage through the gut of P. armata was also studied. No colonies of G. graminis var. tritici and only a few colonies of F. culmorum developed from faecal pellets set on agar medium. Fungal propagules dispersed by springtails were not sufficient to induce disease, as demonstrated by introducing animals, previously fed on fungal cultures separately, into microcosms containing a sterile substrate where wheat kernels were seeded. & 2004 Elsevier GmbH. All rights reserved.