Relative Resistance of 47 Strawberry Cultivars to Powdery Mildew in California Greenhouse and Field Environments. M. D. Nelson, Graduate Student, Department of Plant Pathology, University of California, Davis 95616. W. D. Gubler, Extension Plant Pathologist, Department of Plant Pathology, and Douglas V. Shaw, Associate Professor, Department of Pomology, University of California, Davis 95616. Plant Dis 80:326. Accepted for publication 15 December 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0326.

Forty-seven strawberry cultivars were screened for relative powdery mildew resistance in greenhouse, fruit production field, and propagation nursery trials. Genetic differences contributed a large fraction of the Phenotypic variance among cultivars for powdery mildew severity in all three screening environments (plot-mean H² = 0.89 - 0.93). Powdery mildew reactions were expressed similarly, but not completely, in all three test environments, and greenhouse screening may provide a valuable first step in identifying field-resistant genotypes. Because this trait is highly heritable, considerable potential exists for developing new cultivars with enhanced resistance, and reducing reliance on chemical fungicides for strawberry powdery mildew control