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Molecular Plant Pathology

Chitinolytic Enzymes Produced by Trichoderma harzianum: Antifungal Activity of Purified Endochitinase and Chitobiosidase. M. Lorito,Department of Horticultural Sciences, Entomology, and Plant Pathology, Cornell University, Geneva, NY 14456, Permanent address: Istituto di Patologia Vegetale, Universita' degli Studi di Napoli and Istituendo Centro CNR di Studio delle Tecniche di Lotta Biologica, 80055 Portici (Napoli), Italy; G. E. Harman(2), C. K. Hayes(3), R. M. Broadway(4), A. Tronsmo(5), S. L. Woo(6), and A. Di Pietro(7). (2)(3)(4)(6)(7)Departments of Horticultural Sciences, Entomology, and Plant Pathology, Cornell University, Geneva, NY 14456; (7)Present address: Cátedra de Patologia Vegetal/ETSIAM, Universidad de Córdoba, Spain; (5)Department of Biotechnological Sciences, Agricultural University of Norway, Ås, Norway. Phytopathology 83:302-307. Accepted for publication 12 October 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-302.

Two chitinolytic enzymes from Trichoderma harzianum strain P1 were tested for their antifungal activity in bioassays against nine different fungal species. Spore germination (or cell replication) and germ tube elongation were inhibited for all chitin-containing fungi except T. harzianum strain P1. The degree of inhibition was proportional to the level of chitin in the cell wall of the target fungi. For most of the fungi tested, the ED50 values for the endochitinase and the chitobiosidase were 35–135 ?g ml–1 and 62–180 ?g ml–1, respectively. Complete inhibition occurred at 200–300 ?g ml–1. Combining the two enzymes resulted in a synergistic increase of antifungal activity. The ED50 values for a 1:1 mixture of endochitinase and chitobiosidase were as low as 10 ?g ml–1 for Botrytis cinerea, 34 ?g ml–1 for Ustilago avenae, 13 ?g ml–1 for Uncinula necator, and 30 ?g ml–1 for Fusarium solani, T. harzianum strain P1 was resistant to its own chitinolytic enzymes up to 800 ?g ml–1, with an ED50 value >1,000 ?g ml–1. The chitinolytic enzymes from T. harzianum appeared to be biologically more active than enzymes from other sources and more effective against a wider range of fungi. The involvement of these chitinolytic enzymes in biocontrol is also discussed.

Additional keywords: biological control, fungitoxic compounds, mycoparasitism.