Trophic interactions between soil fungi and Collembola

Collembola are important components of soil mesofauna, abundant in natural and agricultural soils where they fed on fungal propagules and organic matter colonised by fungi. These animals interact with mycoparasitic, arbuscular mycorrhizal (AMF), and phytopatogenic fungi, they cdeeply influence plant growth and health; however knowledge in this field are still scarce. The aim of our research was to investigate interactions between different species of soil fungi and Collembola in vitro, and in planta. The studies in vitro were carried out introducing springtails in Petri dishes, each containing different fungi growing on agarised medium. In this way animals interacted contemporaneously with Fusarium culmorum (Fc), Gaeumannomyces graminis tritici (Ggt), Bipolaris sorokiniana (Bs) and Rhizotonia cerealis (Rc), some of the most important foot and root fungal pathogens of winter cereals world-wide. In some experiments Bs was replaced by the mycoparasitic fungus Trichoderma harzianum (Th). The results of these studies showed that collembolans Protaphorura armata, Mesaphorura krausbaueri, Onychiurus tuberculatus, and Folsomia candida grazed preferably on the mycelium of Fc, but Ggt and Rc hyphae were also consumed. Bs mycelium had repellent and/or lethal effect on animals, Th mycelium repellent, whereas conidia of both fungi were palatable. A diet based on Fc, Ggt, and Rc mycelium or Bs conidia showed different impact on the life processes of M. krausbaueri. The fate of conidia during gut passage was also considered. The majority of Th conidia were not damaged during transit through the gut, and thus they were viable and formed colonies. On the contrary, transit through gut damaged the conidia of Fc. microcosms studies that P. armata grazing activity significantly control disease caused by Fc or Ggt on wheat seedlings. The compatibility between Th and springtails in presence of Ggt was investigated in tests carried out under controlled conditions in the glasshouse. It has been observed that when Th propagules coated wheat seeds, the biocontrol effect of springtails against the disease caused by Ggt was high. On the contrary, when Th inoculum was mixed with the substratum, the animals were not able to control disease severity. In all experiments the biomass of wheat plants was not reduced by springtails. The interactions between Colllembola and AMF Glomus intraradices are still under investigations. From preliminary results, springtails seem compatible with the biocontrol effect of AMF.