Fungicidal activity of secondary metabolites from Annulohypoxylon sp. against the rice blast fungus, Pyricularia oryzae

Rice blast, a devastating disease caused by the fungusPyricularia oryzae, causes major losses to rice production, but it continuously evolves resistance against fungicides. Therefore, natural compounds need to be identified to develop new agents to control fungal pathogens. An ethyl acetate extract of a culture filtrate (S712-ECF) from isolate S712, a member of Polyporaceae collected from a paddy field in Shimane Prefecture in 2009, was sprayed on rice leaves 24 h before inoculation with conidia ofP. oryzae. S712-ECF significantly suppressed blast lesion formation on leaves. Analysis of the internal transcribed spacer (ITS)-5.8S rDNA sequence of S712 showed that it shared high similarities with species of the fungusAnnulohypoxylon. S712-ECF significantly inhibited in vitro conidial germination ofP. oryzaein a dose-dependent manner and had a fungicidal effect againstP. oryzae. Growth inhibition zones ofP. oryzaewere detected in thin layer chromatography assays of S712-ECF. The most effective compound in S712-ECF was heat-stable with a molecular weight < 3000 Da. Secondary metabolites of isolate S712 thus have potential for developing a new fungicidal agent againstP. oryzae.