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Factors Affecting Bioassay of Potato Virus M in Red Kidney Bean. C. Hiruki, Associate Professor, Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2E3; E. Pountney(2), and K. N. Saksena(3). (2)(3)Former Laboratory Technologist, and Former Postdoctoral Fellow, Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2E3, (3)Present address: Division of Sponsored Research, Carnegie Mellon University, Pittsburgh, Pa. 15213 U.S.A. Phytopathology 64:807-811. Accepted for publication 28 December 1973. DOI: 10.1094/Phyto-64-807.

When Carborundum-dusted primary leaves of bean (Phaseolus vulgaris ‘Red Kidney’) were inoculated with potato virus M (PVM), more lesions resulted from 0.057 M phosphate buffer at a range of pH 7.0 - 8.0 as a diluent than from other diluents tested. Plants grown at a light intensity of 5,380 lx (500 ft-c) were most susceptible to PVM. Susceptibility, which was low with juvenile primary leaves, increased as the plant grew, and then declined, showing a plateau 10-12 days after sowing in summer and 14-15 days in winter. A linear relationship existed between dilutions of 10^–1 to 10^–4 of infectious leaf sap and the PVM infectivity. Inocula differing in PVM content by 15% or more, yielded statistically significant differences in lesion number when tested on 36 opposite half-leaves.