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Quantitative Inoculation with Erysiphe pisi to Assess Variation of Infection Efficiency on Peas. P. Reeser, Research assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; D. J. Hagedorn(2), and D. I. Rouse(3). (2)(3)Professor, and assistant professor, respectively, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 73:1238-1240. Accepted for publication 15 February 1983. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1238.

Two techniques were developed for quantitative inoculation of pea (Pisum sativum) with the powdery mildew fungus, Erysiphe pisi. In the first, a liquid carrier composed of 0.0025% Tween-20 in 0.1% water agar was used. In the second, dry Sephadex G-25 (fine grade) was the inoculum carrier. The liquid inoculum was used in tests designed to differentiate resistant and susceptible pea isolines and to identify the stage in the infection process where resistance was expressed. The dry Sephadex inoculum carrier was also used successfully, although variability within replicates was higher than for the liquid carrier.