Does substrate water content influence the effect of Collembola-pathogenic fungus interaction on plant health? A mesocosm study

The effect of interaction between the springtail Protaphorura armata (Tullberg) (Collembola Onychiuridae), and the foot and root pathogenic fungus Gaeumannomyces graminis Von Arx et Olivier var. tritici Walker on number, dry biomass and health of wheat seedlings under two substrate water content levels was studied in a mesocosm experiment. Adult specimens of P. armata were added to each container consisting in metallic frame enveloped by a wrap to prevent the passage of animals, filled with sand previously inoculated with G. graminis var. tritici propagules, where, immediately before the springtails addition, wheat kernels were sown. Containers were placed in plastic boxes (mesocosms) provided by a system of watering regime regulation. The sand moisture content was set up at 5 or 15%, which are the lowest and the highest level respectively of available water for plants in a 100% sandy substrate. Mesocosms were maintained in a growth chamber at 12 hours light, 22 °C temperature, and 60% RH for three weeks. Then wheat seedlings were collected, counted, and disease index and dry biomass determined. At 15% water content, in presence of P. armata the disease severity was lower than that of plants grown in presence of the pathogenic fungus and in absence of animals. At 5% water content, no differences between plant parameters in presence or absence of Collembola were found.