Influence of Pleurotus spent mushroom substrate on root-knot nematode infection and soil microbial dynamics

ABSTRACT Spent mushroom substrate (SMS) offers a sustainable approach to managing plant-parasitic nematodes, particularly root-knot nematodes (RKNs; Meloidogyne spp.), which cause severe root damage and yield loss in crops including Capsicum spp. This research investigated the effect of Pleurotus spp. The SMS on chili root-knot disease and the dynamic of the soil bacterial community of six treatments which are sterile soil with Meloidogyne spp. inoculation (SN), sterile soil control (SC), live soil with nematode inoculation (LN), live soil control (LC), live soil mixed with 15% SMS and nematode inoculation (MN), and live soil mixed with 15% SMS control (MC). Before treatment application, the antagonistic activity of Pleurotus spp. was evaluated, revealing RKN-inhibitory effects, with about 40% immobilization of second-stage juveniles (J2) by mycelium after 24 h and up to 67.5% paralysis caused by the fungal culture filtrate. Pleurotus SMS-amended soil treatments reduced root gall formation by approximately 85%-90%. Regarding changes in the bacterial community, it was found that bacterial communities profiling revealed that the application of SMS had no negative impact on soil bacterial diversity. Bacterial community composition differed markedly between sterilized and live soils, while SMS-amended soil treatments closely resembled live soils, with higher relative abundances of Actinobacteriota (41%-48%) and detectable Acidobacteriota (3%-4%), groups associated with soil health and plant growth promotion. In contrast, sterilized soil treatments were dominated by Bacilli (49%-56%). These findings indicated that SMS play a crucial role in promoting plant growth and assisting in RKN control without affecting the indigenous soil bacterial community.