VIEW ARTICLE

Floral Induction and Development in Poa pratensis Infected with Ustilago striiformis var. poae and Urocystis agropyri. Clinton F. Hodges, Associate Professor of Horticulture and Agronomy, Departments of Horticulture and Agronomy, Iowa State University, Ames 50010; Phytopathology 61:1373-1376. Accepted for publication 23 June 1971. DOI: 10.1094/Phyto-61-1373.

Ustilago striiformis var. poae and Urocystis agropyri inhibited rate of appearance, number, and size of inflorescences produced on Poa pratensis ‘Merion’. Control and smutted plants given floral induction treatments of 30, 60, 90, and 120 days at 12 C and 10-hr day-length produced increasing numbers of shorter tillers as length of induction increased. Inflorescences were produced on control plants after a minimum of 60 days’ induction, and on smutted plants after a minimum of 90 days’ induction. Inflorescences increased on stripe-smutted plants as induction was increased from 90 to 120 days; flag-smutted and control plants produced fewer inflorescences under the same conditions. Sori occurred in inflorescences of stripe-smutted plants subjected to a minimum of 120 days’ induction; few sori were observed in inflorescences of flag smutted plants after 90 and 120 days’ induction. Smutted inflorescences were often aborted; sori occurred in rachises, glumes, lemmas, ovaries, and developing caryopses. Seed set on smutted plants was greatly reduced. Seeds from smutted plants produced seedlings that were smut-free.