Genotype-dependent effects of Pochonia chlamydosporia on Pratylenchus brachyurus suppression in soybean

Pratylenchus brachyurus is a major plant-parasitic nematode that reduces soybean productivity, as most commercial cultivars are susceptible. In this context, Pochonia chlamydosporia has emerged as a promising biological control agent. We investigated the genotype-dependent responses of two soybean cultivars, MG/BR46 (susceptible) and BRS7380 (low reproduction factor), to co-inoculation with P. chlamydosporia and P. brachyurus. Greenhouse experiments combined with targeted metabolite profiling were conducted at 7, 21, and 56 days after nematode inoculation (DAI) to elucidate early biochemical mechanisms underlying fungal-mediated suppression. The fungus controlled the nematode in a distinctly genotype-dependent manner, reducing the nematode population by 48% in MG/BR46, while unexpectedly increasing nematode numbers by 66% in BRS7380 at 80 DAI. Metabolic analyses revealed that MG/BR46 roots underwent hormonal adjustments favouring fungal establishment (reduced JA, SA, and IAA levels), alongside enhanced accumulation of defense-related metabolites (glyceollins I and II and coumestrol). In contrast, BRS7380 exhibited metabolic and structural conditions unfavourable to fungal colonisation, including early JA elevation, increased lignification, higher levels of glyceollins, and reduced coumestrol accumulation. Thus, our results demonstrate that the effectiveness of P. chlamydosporia in suppressing P. brachyurus is shaped by the host’s biochemical and physiological background, highlighting the importance of cultivar selection in optimising biological control.