Fungivorous nematode Aphelenchus avenae and collembola Hypogastrura perplexa alleviate damping-off disease caused by Pythium ultimum in tomato

Purpose Soil fauna are potential regulators of plant pathogens and soil nutrient cycles. However, direct evidence demonstrating faunal controls over pathogens and plant diseases is still limited. Interactions between diverse faunal groups, soilborne pathogen, and microbial community remain elusive. Methods The fungivorous nematode Aphelenchus avenae, two collembolan species (Hypogastrura perplexa and Sinella curviseta), and their combinations were introduced to test their suppression effects on the soilborne fungus Pythium ultimum in tomato, and impacts on microbial biomass and activities in soil. Results The introduction of A. avenae, H. perplexa and combinations of three faunal species decreased tomato seedlings damping-off incidence, and nematode suppressed P. ultimum population in the microcosms. The damping-off disease suppression efficiency is different between faunal treatments, with A. avenae and diverse faunal treatments were more efficient, followed by H. perplexa. The disease suppression effects of S. curviseta were poor. This may be attributed to the non-specific feeding preference of collembolan, different spatial niches and body size of three species. Furthermore, A. avenae and H. perplexa inoculation increased the soil respiration. S. curviseta increased the microbial biomass carbon and nitrogen in microcosms compared with other faunal treatments. These suggest that activities of soil fauna may promote microbial turnover and nutrient cycling to alleviate plant disease. Conclusion Fungivorous nematode A. avenae and collembola H. perplexa can promote the activities of soil microbes, and alleviate damping-off disease incidence caused by P. ultimum in tomato. Effective management of soil fauna is recommended to control root pathogens and maintain tomato health in organic farming systems.