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Ecology and Epidemiology

Epiphytic Movement and Survival of Pseudomonas syringae on Spring Wheat. S. J. Fryda, Former Research Assistant, Department of Plant Science, South Dakota State University, Brookings, SD 57007; J. D. Otta, Associate Professor of Plant Science, Department of Plant Science, South Dakota State University, Brookings, SD 57007. Phytopathology 68:1064-1067. Accepted for publication 20 January 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1064.

Field, greenhouse, and growth chamber experiments demonstrated that Pseudomonas syringae, the incitant of bacterial leaf necrosis of wheat, moved from inoculated wheat seed to the seedling and survived as an epiphyte on the leaves. In greenhouse studies, 80-98% relative humidity favored movement of P. syringae to aerial parts of the seedlings. Movement was not different on wheat cultivars susceptible or resistant to bacterial leaf necrosis. Under 70-98% relative humidity in a growth chamber, P. syringae moved to a significantly higher (P = 0.01) percentage of seedlings at 10 C than at 16 or 22 C. In the field, with a serotype VI isolate as a marker, seedborne P. syringae was recovered from Bounty 208 wheat first true leaves, but not from upper leaves up to 43 days after emergence. From date of seedling emergence to day 41, total precipitation received was only 1.09 cm. After a rainfall of 3.48 cm on day 42, other P. syringae serotypes (III, IV, and V) were isolated from upper leaves. This suggests that other sources of inoculum for bacterial leaf necrosis also were present.