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Comparative Primary Infection Characteristics of Ustilago striiformis and Urocystis agropyri on Cultivars of Poa pratensis. Clinton F. Hodges, Professor of Horticulture and Botany and Plant Pathology, Department of Horticulture, Iowa State University, Ames 50011; Phytopathology 66:1111-1115. Accepted for publication 1 March 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1111.

The ability of Ustilago striiformis and Urocystis agropyri teliospores to initiate primary infections via coleoptiles and axillary buds on several cultivars of Poa pratensis was examined. Urocystis agropyri initiated primary infections more aggressively than U. striiformis. Seed inoculations with U. agropyri reduced seed germination and resulted in greater numbers of coleoptile-infected plants than seed inoculations with U. striiformis. Axillary bud infection by U. agropyri occurred more rapidly, produced more infected shoots, and resulted in greater proliferation of leaf-smutted shoots than did axillary bud infection by U. striiformis. Evaluations of individual cultivars of P. pratensis indicate that many are equal to or exceed Merion in their potential susceptibility to primary infection by U. striiformis and U. agropyri. Many of the newer cultivars also seem capable of greater proliferation of systemically infected shoots than Merion. Cultivars showed a considerable range of susceptibility to U. striiformis and U. agropyri.

Additional keywords: epiphytology, etiology, leaf smuts, resistance.