Direct antagonistic activity and tomato resistance induction of the endophytic fungus Acrophialophora jodhpurensis against Rhizoctonia solani

Abstract

In this study, potential of Acrophialophora jodhpurensis (Chaetomium jodhpurense Lodha) in suppressing Rhizoctonia solani, as a necrotrophic phytopathogenic fungus causing tomato root and crown rot, was investigated in vitro and in vivo conditions. The isolate of A. jodhpurensis inhibited growth of R. solani AG4-HG II in dual culture, and produced volatile and non-volatile metabolites. Light and electron microscopy revealed alternations in the pathogen structures in presence of A. jodhpurensis. Root colonization by A. jodhpurensis reduced the disease index more than 40% compared to the controls. This endophytic fungus reduced the disease index not only via direct antagonism on the pathogen, but also indirectly via inducing resistance mechanisms in the host plant. Indirect effects of A. jodhpurensis against the pathogen in vivo were due to activation of tomato defense responses, such as induction of antioxidant enzymes (including guaiacol peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) activities), phenolic contents, lignin accumulation, relative water content, cell membrane stability, accumulations of hydrogen peroxide (H2O2), superoxide (O2−) and iron ions. Therefore, application of A. jodhpurensis can be applied as a biocontrol agent for protecting tomato plants against R. solani.