Studies on antagonism of Trichoderma species to Fusarium oxysporum f.sp. fragariae, 2; effects of nutrient and environment on antagonistic activity

This experiment was aimed to examine factors affecting mycoparasitism of Trichoderma harzianum isolate T42 or T17 and antibiosis of T. viride isolate T34 or T74 on Fusarium oxysporum f.sp. fragariae in relation to nutrition and physical environment in vitro. Maltose and Ca(NO3)2 were best for the mycoparasitism of T. harzianum as a carbon and nitrogen source, respectively, and KH2PO4 was also an effective element. The mycoparasitism was enhanced in high carbon and low nitrogen medium. Addition of organic materials such as corn, wheat bran and rice straw powder increased the mycoparasitism, whereas clover leaf powder amendment annulled the efficiency. Addition of cell walls of the pathogen, cellulose or chitin in the cultures also enhanced the lysis of both hyphae and conidia of the pathogen by T. harzianum. Optimal culture conditions for the mycoparasitism appeared in the pH range of 3.5 to 5.5 at 25deg C. T. viride produced non-volatile antibiotics in culture media, which inhibited mycelial growth of F. oxysporum f.sp. fragariae, but its antagonistic effect was relatively low. Carbon source was required for its inhibitory effect while the other nutritional factors and environmental factors had no effect