Isolates of endophytic <i>Chaetomium</i> spp. inhibit the fungal pathogen <i>Pyrenophora tritici-repentis</i> in vitro

Abstract

Growth of a culturable pathogen, Pyrenophora tritici-repentis (Died.) Drechs., was inhibited by six isolates of endophytic Chaetomium spp. in vitro when grown in apposition. Metabolites of the endophytes, when grown either on agar or in liquid media, also inhibited the pathogen. The culture filtrate of Chaetomium was extracted in 70% ethanol, and the ethanol-soluble fraction that either passed through a molecular sieve of 3000 molecular mass cutoff or was held on 30 000 molecular mass cutoff inhibited the pathogen. The high molecular mass fraction was a protein with one major band at 29 kDa. The electroeluted band delayed the growth of the pathogen in vitro. Inhibition was retained in filtrate stored frozen, as dried residue, and when rehydrated after drying. Autoclaving reduced, whereas proteinase K treatment did not affect, the activity of the proteinaceous fraction. The data support the hypothesis that endophytic Chaetomium produce a range of metabolites that inhibit P. tritici-repentis in vitro and may affect the pathogen when the fungi co-occur in wheat.