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Tiller and Rhizome Growth of Water-Stressed Poa pratensis 'Merion' Infected by Ustilago striiformis or Urocystis agropyri. Jeff L. Nus, Department of Horticulture, Kansas State University, Manhattan 66506. Clinton F. Hodges, Department of Horticulture, Iowa State University, Ames 50011. Plant Dis. 74:886-888. Accepted for publication 7 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0886.

Growth of tillers and rhizomes of Poa pratensis 'Merion' infected by Ustilago striiformis (cause of stripe smut) or Urocystis agropyri (cause of flag smut) was evaluated in nutrient solution alone and amended with polyethylene glycol to provide increasing levels of osmotically induced water stress. U. striiformis had no effect on total dry weight of rhizomes per shoot but decreased the percentage of rhizome dry weight as a portion of total shoot dry weight. Dry weight of tillers per shoot increased and was a greater percentage of total shoot dry weight than the percentage of total shoot dry weight in healthy plants. U. agropyri decreased rhizome growth and increased tiller growth expressed as total dry weight per shoot or as the percentage of total shoot dry weight when compared to healthy plants. Stimulation of tiller growth induced by U. striiformis was negated with increased water stress, but tiller stimulation induced by U. agropyri persisted under severe water stress.