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Physiology and Biochemistry

Permeability Changes in Hyphae of Rhizoctonia solani Induced by Germling Preparations of Trichoderma and Gliocladium. J. A. Lewis, Soilborne Disease Laboratory, Plant Protection Institute, U.S. Department of Agriculture, Beltsville, MD 20705; G. C. Papavizas, Soilborne Disease Laboratory, Plant Protection Institute, U.S. Department of Agriculture, Beltsville, MD 20705. Phytopathology 77:699-703. Accepted for publication 6 October 1986. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1987. DOI: 10.1094/Phyto-77-699.

Water extracts of germlings (young, actively growing hyphae on bran) of isolates of Trichoderma spp. and Gliocladium virens affected growth of Rhizoctonia solani (R-23) in liquid culture. Bran control and germling extracts from 7 of 14 isolates increased mycelium weight up to fourfold. Extracts from one T. viride isolate (TS-1-R3), one T. hamatum isolate (31-3), and all four G. virens isolates (Gl-3, Gl-9, Gl-17, Gl-21) prevented growth as effectively as 0.2 mM HgCl2. Similar results were obtained with three other isolates of R. solani investigated. Leakage of compounds from mycelial mats of R-23 was induced after mats were exposed to germling extracts of T. harzianum (Th-5), T. hamatum (Tm-23, 31-3), or G. virens (Gl-3, Gl-9, Gl-17, Gl-21) for less than 0.5 hr. The chemical composition of the leaked materials (soluble protein, carbohydrate, amino acids, salts) was determined by colorimetry and conductance. Leakage was accompanied by a reduction in the mycelial weight of R-23. The rate of leakage indicated an immediate and gradually increasing loss of materials from pathogen hyphae. Extracts from young germling preparations induced more leakage than extracts from older bran preparations or conidia on bran. Heat treatment of extracts (121 C) reduced leakage by 7580%. Addition of Gl-21 germlings to soil containing noninfested beet seed or seed infested with R-23 resulted in production of membrane-altering substances in the seed extracts that induced leakage from mycelial mats of R-23.