Synergistic interaction between fungal cell wall degrading enzymes and different antifungal compounds enhances inhibition of spore germination

Departments of Horticultural Sciences and Plant Pathology, Cornell University, Geneva, NY 14456, USA ABSTRACT Different classes of cell wall degrading enzymes produced by the biocontrol fungi Trichoderma harzianum and Gliocladium virens inhibited spore germination of Botrytis cinerea in a bioassay in vitro . The addition of any chitinolytic or glucanolytic enzyme to the reaction mixture synergistically enhanced the antifungal properties of five different fungitoxic compounds against B. cinerea . The chemicals tested were gliotoxin, flusilazole, miconazole, captan and benomyl. Dose response curves were determined for each combination of toxin and enzyme, and in all cases the ED 50 values of the mixtures were substantially lower than ED 50 values of the two compounds used alone. For instance, the addition of endochitinase from T. harzianum at a concentration of 10 g ml -1 reduced the ED 50 values of toxins up to 86-fold. The level of synergism appeared to be higher when enzymes were combined with toxins having primary sites of action associated with membrane structure, compared with pesticides having multiple or cytoplasmic sites of action. Among enzymes tested, the highest levels of synergism with synthetic fungicides were detected for the endochitinase from T. harzianum strain P1, which, when used alone, was the most effective chitinolytic enzyme against phytopathogenic fungi of those tested. The use of hydrolytic enzymes to synergistically enhance the antifungal ability of fungitoxic compounds may reduce the impact of some chemical pesticides on plants and animals. Keywords: Borrytis cinerea, biocontrol fungi, synergistic interaction, antifungals, cell wall degrading enzymes Permanent address: lnstitut fur Biochemische Technologie und Mikrobiologie, Technische Universitat Wien, Wien, Austria. Permanent address: lstituto di Patologia Vegetale, Universita degli Studi di Napoli, and lstituendo Centro CNR di Studio delle Tecniche di Lotta Biologica, 80055 Portici (Napoli), Italy.