Aspergillus sp. R3, a new producer for cyclopyazonic acid, inhibits rice sheath blight fungus Rhizoctonia solani Kühn

Abstract

This study investigated the activity of the novel Aspergillus sp. R3 against rice sheath blight (RSB) fungus Rhizoctonia solani Kühn. R3 strain had strong antagonistic activity. R3 strain was Aspergillus sp. by morphological observation and molecular identification. After enrichment, separation, purification and nuclear magnetic resonance (NMR) identification of culture solution and mycelium of Aspergillus sp. R3, the main metabolite was identified as cyclopyazonic acid (CPA). We studied the effect of CPA on R. solani, including mycelial morphology, membrane permeability and lipid peroxidation. The control effect of CPA on rice seedlings infected with sheath blight was also tested. CPA inhibited the growth of R. solani in vitro and led to the atrophy of R. solani mycelia under microscopic observation. In addition, CPA exhibited antimicrobial activity against a variety of plant pathogens in vitro. With the treatment of CPA with R. solani, the malondialdehyde content and electrolyte leakage of R. solani mycelia increased compared with the control. Additionally, CPA could significantly reduced the severity of sheath blight disease of rice seedlings infected with R. solani. This is the first report of the CPA produced by Aspergillus sp. with antagonistic activity against R. solani and R. solani-induced RSB. This study indicates that Aspergillus sp. and its metabolites may serve as potential biocontrol agents against some plant pathogens.