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Biological Control

Detrimental Effects of Sublethal Heating and Talaromyces flavus on Microsclerotia of Verticillium dahliae. E. C. Tjamos, Department of Plant Pathology, Agricultural University of Athens, Votanikos 11855, Athens, Greece; D. R. Fravel, Biocontrol of Plant Diseases Laboratory, USDA, ARS, Beltsville, MD 20705. Phytopathology 85:388-392. Accepted for publication 27 December 1994. 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, 1995. DOI: 10.1094/Phyto-85-388.

Microsclerotia of Verticillium dahliae were not heated or heated in water with one of three regimes to simulate soil solarization. Regime 1 consisted of 31 C for 10 h followed by 35 C for 14 h. Regime 2 consisted of 33 C for 10 h followed by 36 C for 14 h. Regime 3 consisted of 35 C for 10 h followed by 38 C for 14 h. Heating for 1–5 days with regime 1 did not affect the final number of microsclerotia that germinated but did affect the rate at which they germinated. Additional days of heating with regime 2 or 3 affected both the number of germinated microsclerotia and the rate at which they germinated. Of the microsclerotia that germinated, colonies arising from heated microsclerotia formed significantly fewer melanized microsclerotia and melanization of these new microsclerotia was significantly slower than for those originating from the nonheated microsclerotia. When microsclerotia were heated as above, placed in nylon mesh envelopes, and buried in raw soil with or without the biocontrol agent Talaromyces flavus, there was a synergistic interaction between the heating and T. flavus resulting in increased mortality of the microsclerotia. Colonies arising from surviving, previously heated microsclerotia were slower growing than colonies from nonheated micro-sclerotia and were slower to form melanized microsclerotia. Sublethal heating and T. flavus acted additively to suppress Verticillium wilt of eggplant. Opportunities for combining sublethal heating with thermophilic biocontrol agents are discussed.