Fungivorous Nematodes and Collembola Alleviate Disease Incidence Caused by Pathogen Pythium Ultimum in Tomato

Abstract Purpose Soil fauna are potential biological regulators of plant pathogens and soil nutrient cycles; however, the direct evidence demonstrating faunal controls over pathogens and plant diseases are still limited and the interactions between diverse faunal groups, soil-borne pathogen and microbial community remain elusive. Methods We introduced the nematode Aphelenchus avenae, two collembolan species (Hypogastrura perplexa and Sinella curviseta) and their combinations to test their suppression effects on the soil-borne fungus Pythium ultimum in tomato seedlings, and impacts on the biomass and activities of soil microbes. Results The introduction of A. avenae, H. perplexa and combinations of three faunal species showed significant suppression on P. ultimum population and decreased tomato seedling damping-off incidence, and diverse soil faunal species had the greatest suppression. The suppression efficiency is significantly different among the faunal species, with A. avenae was the most efficient, followed by H. perplexa, and the suppression effects of S. curviseta were poor. This may be attributed to the non-specific feeding behavior of collembolan, different spatial niches and body size of three faunal species. Furthermore, the presence of S. curviseta and H. perplexa increased the microbial biomass carbon and nitrogen, and A. avenae increased the soil respiration in microcosms, suggesting that activities of soil fauna may promote microbial turnover and nutrient cycling to alleviate plant disease. Conclusion Effective management of soil fauna can facilitate the control of root pathogens and stimulate soil microbes in organic farming systems. Future sustainable agricultural management is recommended to examine the applications of soil biodiversity in maintaining plant health and soil fertility in the arable fields.