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Effects of the Systemic Flower Infecting-Smut Ustilago Bullata on the Growth and Competitive Ability of the Grass Bromus Catharticus

Graciela Garcia-Guzman, J. J. Burdon and A. O. Nicholls
Journal of Ecology
Vol. 84, No. 5 (Oct., 1996), pp. 657-665
DOI: 10.2307/2261329
Stable URL: http://www.jstor.org/stable/2261329
Page Count: 9
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Effects of the Systemic Flower Infecting-Smut Ustilago Bullata on the Growth and Competitive Ability of the Grass Bromus Catharticus
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Abstract

1 The effects of the flower infecting-smut fungus Ustilago bullata on the performance of its host Bromus catharticus were investigated through a series of glasshouse-based experiments. 2 Smut infection resulted in the complete sterility of Bromus catharticus; reduced the overall size of infected individuals regardless of plant density or the relative frequency of healthy and infected individuals; changed the allocation of resources between roots and shoots; and reduced the rate of seedling emergence but not final emergence percentages. 3 Despite these effects, infection did not affect the relative competitive ability of infected plants growing at high nutrient levels as reflected by dry weight accumulation. Here healthy and infected individuals competed equally for the same limiting resources $(k_{hd} = 1 = 1/k_{dh})$. Under low nutrient conditions, however, healthy plants showed an increased competitive ability relative to infected plants $(k_{hd} = 1.52; k_{dh} = 0.66)$. 4 These results are considered in light of the evolutionarily interesting position systemic smut diseases occupy relative to other fungal pathogens and endophytes.

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