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Effects of Cultivar, Leaf Wetness Duration, Temperature, and Growth Stage on Infection and Development of Ascochyta Blight of Lentil. E. A. Pedersen, Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada S7N 0W0, Present address: National Research Council Canada, Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK, Canada S7N 0W9; R. A. A. Morrall, Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada S7N 0W0. Phytopathology 84:1024-1030. Accepted for publication 21 June 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-1024.

Growth chamber tests were conducted on three lentil cultivars susceptible (Eston), moderately resistant (Laird), and resistant (Indianhead) to Ascochyta blight, caused by Ascochyta fabae f. sp. lentis. Leaf wetness after inoculation, temperature, and plant growth stage had significant effects on infection and disease development. The highest infection frequency occurred with a wetness period of 24 or 48 h. For all cultivars, latent periods were shortest (67 days) at 20 C and longest (1314 days) at 10 C. Temperature had little effect on lesion size and number of pycnidia per lesion, but infection frequency was higher at 10 and 15 C than at 25 C. The lowest number of lesions and pycnidia and the smallest lesions occurred on Indianhead at 10, 15, and 20 C. Lesions were fewer and smaller and contained fewer pycnidia on Laird than on Eston at 15 and 20 C but not at 10 C. On stems, the highest number of lesions and pycnidia and the largest lesions were produced on Laird at all temperatures. Based on results of growth chamber and field tests, tissues below the top four or five nodes on the main stem and secondary branches were almost completely resistant in all three cultivars. The effect of this tissue-age-related resistance on disease severity was most apparent at the podding stage.

Additional keywords: components of resistance, controlled conditions, pulse crop.