An endophytic fungus Dichotomopilus funicola J-219 for the control of pigeon pea root rot caused by Rhizoctonia solani and its role in regulating the secondary metabolic defense response

Abstract

Legume root rot caused by Rhizoctonia solani is a devastating fungal disease. The use of endophytic fungi for biological control is considered to be a safe, effective, and environmentally friendly strategy. In the present study, an endophytic fungus J-219 isolated from pigeon pea was found to have significant antagonistic activity against R. solani. The endophytic fungus J-219 was identified as Dichotomopilus funicola. The crude extracts of D. funicola J-219 could significantly inhibit R. solani growth and even cause the collapse of R. solani or disrupt mycelia. D. funicola J-219 could produce antimicrobial compounds of host pigeon pea (genistein, genistin, and cajaninstilbene acid) as well as genus-specific antimicrobial compounds (chaetocin and chaetoglobosins A), which were likely to be the active substances that inhibited R. solani growth. In addition, D. funicola J-219 inoculation could significantly alleviate root rot of pigeon pea seedlings caused by R. solani. Compared to R. solani-infected pigeon pea roots, co-inoculation of D. funicola J-219 and R. solani could significantly reduce the contents of defensive phenolic compounds and the expression levels of pathogenesis- and phenolic biosynthesis-related genes, indicating that D. funicola J-219 could alleviate root rot of pigeon pea seedlings mainly by inhibiting the growth of the pathogen R. solani, rather than inducing the host secondary metabolic defense response to pathogen infection. Overall, the D. funicola J-219 showed promising potential for the control of R. solani root rot of pigeon pea seedlings, which held important implications for the control of legume root rot and provided valuable insights for the development of environmentally friendly biocontrol agents against R. solani root rot.