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Ecology and Epidemiology

Leaf Wettability of Wheat in Relation to Infection by Puccinia recondita f. sp. tritici. G. D. Statler, Professor, Department of Plant Pathology, North Dakota State University, Fargo 58105; J. T. Nordgaard, former graduate student, Department of Plant Pathology, North Dakota State University, Fargo 58105, Current address of junior author: Agvise Inc., Benson, MN 56215. Phytopathology 70:641-643. Accepted for publication 14 December 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-641.

All wheat cultivars tested had significantly more uredia when Tween-20 was added to the incubation chamber water mist, or when the plant leaves were rubbed prior to inoculation. Hard red spring wheat cultivar Thatcher had significantly more pustules than did the durum cultivars Botno and Rolette. There were more uredia at the longest incubation time (24 hr) for all treatments and cultivars. There was a significant correlation between number of uredia and incubation times between 4 and 24 hrs. Rubbing the leaves or the addition of Tween-20 to the water droplet resulted in significant reductions in water droplet contact angles. The angles were not significantly different among cultivars. Leaves from all cultivars that were studied retained significantly more water when leaves were rubbed or dipped in water-dye plus Tween-20 than when undamaged leaves were dipped in water-dye. Rubbing the leaves or the use of Tween-20 in the water mist improved wettability, increased infection, and reduced variability of infection when water mist was used.