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Physiological Characteristics of Systemic Toxemia in Soybean. J. Dueck, Plant Pathologist, Canada Department of Agriculture, Harrow, Ontario, Canada; V. B. Cardwell(2), and B. W. Kennedy(3). (2)Assistant Professor, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul 55101; (3)Associate Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55101. Phytopathology 62:964-968. Accepted for publication 16 February 1972. DOI: 10.1094/Phyto-62-964.

Systemic toxemia in young trifoliolate leaves of soybean is caused by toxin(s) produced in older leaves infected with Pseudomonas glycinea. Symptoms were most severe 6-8 days after inoculation, and affected leaves could partially recover. Systemic toxemia could be prevented by steam-killing petioles of inoculated leaves, suggesting that the toxin was translocated in the phloem. Trifoliolate leaves affected by toxemia had a reduced rate of photosynthesis 6-10 days after inoculation, but by the 12th day, their rate of photosynthesis was equal to that of healthy leaves. Although leaves recovered in chlorophyll concentration 10 days after inoculation, stunting was permanent.