ANTAGONISTIC ACTIVITY OF SOME CHAETOMIUM SPECIES AGAINST COMMON BEAN ROOT ROT PATHOGENS

Abstract

Different root rot fungi, i.e. Rhizoctonia solani, Fusarium solani and ,Macrophomina phaseolina in addition to the Oomycete pathogen Pythium sp. were isolated from bean plants showing root rot syndromes collected from Giza and Qalyubiya governorates. Pathogenicity tests ofroot rot pathogens on bean (Giza 6) were carried out. All tested isolates were found to be pathogenic to bean plants.Fourteen isolates of Chaetomiumspp. were collected from Mycology Res. Dept. and 19Chaetomiumisolateswere isolated from different plant hosts. Chaetomiumisolates were identified based on morphological and molecular characterization and werebelonged to 7 species namely; C. globosum, C. bostrychodes, C.madrasense,C. brasiliense, C. atrobrunneum, C. nigricolorandC. megalocarpum. Some isolates of Chaetomiumspp. enhanced the germination ofbeen seeds. Thirty threeisolates of Chaetomium spp. suppressed the radial growth of root rot pathogens. T he mode of action of Chaetomium isolatestowards root rot pathogensvaried, some isolates suppressed the growth of the pathogens while some others showed mycoparasitism behaviour. Microscopical observation of antagonistic areas on petri dishes showed lysis of pathogens’ mycelia due to over growth penetration through hyphal pegs and coiling by Chaetomium. Scanning Electronic microscope showed that C. globosum was able to penetrate from different sites of one compartment of R. solani hyphae,. In addition, cytoplasm and protoplast membrane of hyphal cells of R. solani was broken down and organelles were no longer discernible in the highly altered cytoplasm.All partially purified culture filtrates of Chaetomium spp. isolates caused reduction of mycelia dry weight of root rot bean pathogens