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Comparative Morphology and Development of Poa pratensis Infected by Ustilago striiformis and Urocystis agropyri. Clinton F. Hodges, Assistant Professor of Horticulture and Agronomy, Departments of Horticulture and Agronomy, Iowa State University, Ames 50010. Phytopathology 60:1794-1797. Accepted for publication 16 July 1970. DOI: 10.1094/Phyto-60-1794.

Morphological and developmental characteristics of Poa pratensis ‘Merion’ varied in response to infection by Ustilago striiformis (stripe smut) and Urocystis agropyri (flag smut). Laminae of stripe- and flag-smutted plants were more erect than those of control plants. Laminae of stripe-smutted plants were wider than those of control and flag-smutted plants. Lamina thickness was equal for stripe- and flag-smutted plants, and greater than that of control plants. Stripe-smutted plants were taller than controls, whereas, flag-smutted plants were noticeably stunted. Total branches produced by stripe- and flag-smutted plants were less than that of control plants. Stripe-smutted plants showed the greatest reduction in total branching. Flag-smutted plants produced proportionally more intravaginal branches than did either control or stripe-smutted plants, indicating premature axillary crown bud break in response to U. agropyri. Extravaginal branching was proportionally higher among control and stripe-smutted plants. Total dry-matter production of flag-smutted plants was less than that of control and stripe-smutted plants. Root dry weight of stripe- and flag-smutted plants was less than that of controls; however, reduction of roots among flag-smutted plants was greater than among stripe-smutted plants.