Biocontrol potential of Waitea circinata, an orchid mycorrhizal fungus, against the rice blast fungus

Abstract

Rice blast (Magnaporthe oryzae) occurs in rice producing areas worldwide. Microorganisms are capable of producing secondary metabolites that can control the pathogen. The present study aimed to identify the class of the secondary metabolites produced by the mycorrhizal fungus Waitea circinata obtained from a Cerrado orchid and to assess the in vitro and in vivo antagonism of the extracts against M. oryzae. Three mycorrhizal extracts (crude, mycelial and lyophilized) were obtained. In the in vitro antagonism assay, W. circinata produced the largest inhibition zone. The crude extract reduced the mycelial growth of the pathogen by 75 %, inhibited the formation of appressoria by 100 % and reduced the AUDPC by 25 % compared to the control. Analysis of the crude extract by electro spray ionization Fourier transform ion cyclotron resonance mass spectrometry revealed the presence of benzophenones. The results suggest that W. circinata extract has the potential for rice blast control.