Root colonization and effect of biocontrol fungus Paecilomyces lilacinus on composition of ammonia-oxidizing bacteria, ammonia-oxidizing archaea and fungal populations of tomato rhizosphere

This study investigated the effects of root-knot nematode biocontrol agent Paecilomyces lilacinus (P. lilacinus) strain PL1210 on ammonia-oxidizing microorganisms and fungal community composition of tomato rhizosphere. The exchangeable NH4 (+)-N and NO3 (-)-N contents were lower in inoculated soils than in the control during 60 days of incubation. Real-time quantitative polymerase chain reaction (qPCR) detected stable colonization of P. lilacinus in the tomato rhizosphere and significant inhibition of ammonia-oxidizing bacteria (AOB) and archaea (AOA), which could be responsible for the decrease of NO3 (-)-N content in soil. PCR-denaturing gradient gel electrophoresis (DGGE) analysis demonstrated no significant difference in soil fungal community composition associated with the application of P. lilacinus as shown by Shannon-Wiener diversity index (H') and Margalef index (D). Cluster analysis showed that the composition of rhizosphere fungal community was more significantly influenced by time-related differences than by the inoculation of biocontrol agents.