VIEW ARTICLE

Ecology and Epidemiology

Sporulation of Uncinula necator on Grape Leaves as Influenced by Temperature and Cultivar. D. O. Chellemi, Graduate research assistant, Plant Pathology Department, University of California, Davis 95616, Present address: University of Florida-IFAS, North Florida Research and Education Center, Route 3, Box 4370, Quincy, FL 32351; J. J. Marois, Associate professor, Plant Pathology Department, University of California, Davis 95616. Phytopathology 81:197-201. Accepted for publication 25 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-197.

Sporulation of Uncinula necator on grapevines (Vitis vinifera 'Carignane' and 'Chardonnay') was quantified at 19, 22, 26, and 30 C by harvesting conidia at periodic intervals from individual colonies. Temperature was shown to influence the length of the infectious period. Colonies began sporulating 5 days after inoculation, except at 19 C, when sporulation was first observed after 7 days. Sporulation stopped by 35, 35, 25, and 20 days after inoculation at 19, 22, 26, and 30 C, respectively. Sporulation was greater on Carignane than Chardonnay at all temperatures except 19 C. The maximum number of conidia produced per colony was 11,450. The Richards function was used to describe observed cumulative sporulation over time. The time at which the maximum sporulation rate of colonies occurred, as determined by the inflection point, was influenced by temperature and cultivar. Inflection points ranged from 14.7 days at 30 C to 25.5 days at 19 C.