Antagonistic fungi producing hydrolytic enzymes, active in degrading the cell wall of some foot rot pathogens (Fusarium spp.) of wheat

The antagonistic fungi Gliocladium roseum 11, Penicillium frequentans, Trichoderma atroviride 312, T harzianum 144 and T. longibrachiatum 9 were grown with cell wall constituents of the foot rot pathogens Fusarium avenaceum, F. culmorum, F. graminearum and F nivale as sole sources of carbon. Production ofthe hydrolytic, cell wall-degrading enzymes N-acetyl-β-D-glucosaminidase, chitin 1,4-β-chitobiosidase, glucan 1,3-β-glucosidase and protease was assayed in culture filtrates. All antagonists produced the chitin and glucan-degrading enzymes when grown in presence of all the pathogens. The highest level of N-acetyl-β-D-glucosaminidase (19.52 ± 0.057 U and 19.10 ± 0.258 U) were recorded for G. roseum 11 in combination with cell walls of F. graminearum and F. nivale, while the highest level of chitin 1,4-β-chitobiosidase activity (9.38 ± 1.714 U) was determined for G. roseum 1 1 in combination with F culmorum. Compared to G. roseum 11, Trichoderma spp. and P. frequentans produced relatively low levels of these enzymatic activities. Regarding the glucan 1,3-β-glucosidase activity, T. atroviride 312 generally showed the highest level of activity, mostly pronounced with cell walls of F. graminearum (51.98 ± 2.37 U). P. frequentans showed a consistent production of protease, while only a few of the other combinations of antagonists and pathogens produced any detectable level of this enzymatic activity. It is concluded that the above reported enzymatic activities may contribute to explain the parasitism of the antagonists against Fusarium species involved in foot rot disease of wheat, although other modes of action of the antagonists such as antibiosis, competition or induced resistance cannot be excluded.