Occurrence of Race 3 of Peronospora effusa on Spinach in Texas and Identification of Sources of Resistance. R. K. Jones, Plant Pathologist, Texas Agricultural Extension Service, Texas Agricultural Experiment Station, Uvalde 78801. F. J. Dainello, Research Horticulturist, Texas Agricultural Experiment Station, Uvalde 78801. Plant Dis. 66:1078-1079. Accepted for publication 3 June 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-1078.

Race 3 of Peronospora effusa capable of attacking spinach (Spinacia oleracea) resistant to races 1 and 2 has been found in Texas. Race 3 is currently causing severe damage on fresh market savoy spinach. A source of resistance based on the gene designated M₃ has been identified in some breeding lines and commercially available hybrids. A technique suitable for resistance screening is described.

Keyword(s): blue mold, downy mildew, pathogen variability.