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Effect of Light on Reactions of Soybean to Pseudomonas glycinea. Mark A. Smith, Secretary, Crop Quality Council, Minneapolis, Minnesota 55101; Bill W. Kennedy, Associate Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55101 Phytopathology 60:723-725. Accepted for publication 30 November 1969. DOI: 10.1094/Phyto-60-723.

Bacterial leaf blight of bean, cucumber, cotton, and soybean did not develop when susceptible plants were placed in darkness for 5 days after, or 4 days before, the 5 days after inoculation with their respective natural pathogens. As postinoculation light intensity treatments were increased from 50-60 ft-c to 2,000-2,500 ft-c, size and prevalence of susceptible-type lesions increased on the four hosts. In light regimes of similar energy levels, normally susceptible reactions of bacterial blight of soybean did not occur in green or blue light, but developed fully in white, and to a limited extent in red light. Pre-inoculation and postinoculation darkness treatments did not alter development of the resistant (hypersensitive) reaction in soybean varieties inoculated with avirulent races of Pseudomonas glycinea.