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Resistance

Partial Resistance to Uromyces appendiculatus in Dry Edible Beans. Glen D. Statler, Professor, Department of Plant Pathology, North Dakota State University, Fargo 58105; Melinda A. McVey, Research specialist II, Department of Plant Pathology, North Dakota State University, Fargo 58105. Phytopathology 77:1101-1103. Accepted for publication 5 February 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1101.

Partial resistance was studied in five bean (Phaseolus vulgaris) cultivars that appeared to differ in their resistance to leaf rust incited by Uromyces appendiculatus. Inoculated leaves were sampled daily, then cleared and stained for fluorescent microscopy. The factors studied histologically were colony size, early and late colony abortion, proportion of successful penetrations, and uredial size. Cultivars Nodak and Upland had a higher percentage of both early- and late-aborted colonies than the rust-susceptible cultivars Fiesta and UI 114. Nodak and Upland had a lower proportion of successful penetrations than the susceptible cultivars at 14 days. Nodak had smaller colonies than the rust-susceptible cultivars after day 7. Uredia were counted daily to determine infection density (ID) and latent period (LP₅₀). LP₅₀ did not differ significantly among the cultivars studied. The ID and number of uredia per square centimeter were significantly lower for Nodak and Upland than for the susceptible cultivars. Nodak and Pindak had smaller uredia at 14 days than the susceptible cultivars. Partial resistance was documented for Nodak and Upland. The only component of partial resistance demonstrated for Pindak was small uredia.