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Ecology and Epidemiology

Effect of Temperature and Moisture Tension on Growth, Sclerotial Production, Germination, and Infection by Sclerotinia minor. E. D. Imolehin, Research assistant, Department of Plant Pathology, University of California, Davis 95616; R. G. Grogan(2), and J. M. Duniway(3). (2)(3)Professor, and associate professor, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 70:1153-1157. Accepted for publication 19 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1153.

Sclerotial germination and mycelial growth of Sclerotinia minor occurred from 6 to 30 C; the optimum for each was at 18 C. Infection of lettuce tissue by hyphae from germinating sclerotia occurred from 6 to 24 C with an optimum at 18 C. The temperature range for sclerotial formation was from 12 to 24 C with more sclerotia produced at 12 C than at other temperatures, but sclerotia produced at the higher temperatures were larger. Mycelial growth on cornmeal agar occurred at solute potentials of 1 to 73 bars, but sclerotia were formed only within the range of 1 to 43 bars. Growth in liquid media was maximal at about 7 bars and declined at lower solute potentials. Sclerotia produced at various solute potentials and temperatures germinated equally well. Sclerotia were capable of eruptive germination at soil moisture tensions ranging from 1/3 to 15 bars, but the highest percent germination occurred at 1/3 bar. Infection of lettuce tissue by sclerotia at temperatures between 6 and 24 C was dependent on the ability of sclerotia to germinate eruptively. All tissues inoculated with mycelial plugs instead of sclerotia at 6 to 24 C became infected.

Additional keywords: Lactuca sativa.