Activity of Glucanases of Zygorrhynchus moelleri in Relation to Antagonism Against some Soil‐Borne Plant Pathogenic Fungi

Zygorrhynchus moelleri antagonized some soil‐borne fungi on agar and in composts. Filtrates of Z. moelleri cultures contained high levels of β‐1,3‐glucanase (exoglucanase) and β‐1,3(4)‐glucanase (endoglucanase) when the fungus was grown on hyphal wall material from Rhizoctonia solani or Pythium intermedium as sole carbon source. Lower exo‐ and endoglucanase activities were produced on Fusarium oxysporum f. sp. lini (F.o.l.) hyphal walls while insignificant levels were produced on Z. moelleri hyphal walls. Protease was also produced when Z. moelleri was grown on hyphal wall material, but chitinase or cellulase were not detected. Optimum production of both glucanases occurred in media at pH,6 to 7 and activity was optimal at pH 5. The enzymes were active over a temperature range in excess of 20–50 °C but optimum activity occurred at 40 °C. Cell free culture filtrates containing exo‐ and endoglucanase activity lysed living hyphal walls of R. solani, P. intermedium, Verticillium albo‐atrum and F.o.l. although walls of the latter were least sensitive to lytic activity. The culture filtrates did not lyse living mycelium of Z. moelleri. Z. moelleri also produced substances inhibitory to growth of colonies of test fungi on agar. In glasshouse experiments disease severity in flax induced by R. solani and P. intermedium, in parsley by P. paroecandrum and in radish and Zinnia by P. intermedium was suppressed in composts inoculated with sporangiospore suspensions of Z. moelleri.