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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.