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Resistance of Apple to Powdery Mildew and Its Relationship to Osmotic Activity of the Cell Sap. Jan Cimanowski, Postdoctoral Fellow, Department of Plant Pathology, University of Missouri, Columbia 65201; D. F. Millikan, Professor, Department of Plant Pathology, University of Missouri, Columbia 65201. Phytopathology 60:1848-1849. DOI: 10.1094/Phyto-60-1848.

High osmotic values of cell sap are associated with resistance of apple to powdery mildew. This relationship occurs within a single variety in comparisons between young susceptible and old resistant leaves and among four clones of McIntosh having different levels of resistance. Other unidentified physiological factors appear to contribute to the resistance mechanism.