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Environmental factors influencing Pyrenophora semeniperda-caused seed mortality in Bromus tectorum

Published online by Cambridge University Press:  20 November 2012

Heather Finch ,
Phil S. Allen  and
Susan E. Meyer
Heather Finch*
Affiliation:
Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT84602, USA
Phil S. Allen
Affiliation:
Department of Plant and Wildlife Sciences, Brigham Young University, Provo, UT84602, USA
Susan E. Meyer
Affiliation:
Rocky Mountain Research Station, Forest Service, United States Department of Agriculture, Shrub Sciences Laboratory, Provo, UT84606, USA
*
*Correspondence E-mail: heatherf7@gmail.com
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Abstract

Temperature and water potential strongly influence seed dormancy status and germination of Bromus tectorum. As seeds of this plant can be killed by the ascomycete fungus Pyrenophora semeniperda, this study was conducted to learn how water potential and temperature influence mortality levels in this pathosystem. Separate experiments were conducted to determine: (1) if P. semeniperda can kill dormant or non-dormant seeds across a range of water potentials (0 to − 2 MPa) at constant temperature (20°C); and (2) how temperature (5–20°C) and duration at reduced water potentials (0–28 days) affect the outcome. When inoculated with the fungus at 20°C, all dormant seeds were killed, but fungal stromata appeared more quickly at higher water potentials. For non-dormant seeds, decreasing water potentials led to reduced germination and greater seed mortality. Results were similar at 10 and 15°C. Incubation at 5°C prevented stromatal development on both non-dormant and dormant seeds regardless of water potential, but when seeds were transferred to 20°C, dormant seeds evidenced high mortality. For non-dormant seeds, exposure to low water potential at 5°C resulted in secondary dormancy and increased seed mortality. Increasing incubation temperature, decreasing water potential and increasing duration at negative water potentials all led to increased mortality for non-dormant seeds. The results are consistent with field observations that pathogen-caused mortality is greatest when dormant seeds imbibe, or when non-dormant seeds experience prolonged or repeated exposure to low water potentials. We propose a conceptual model to explain the annual cycle of interaction in the Bromus tectorum–Pyrenophora semeniperda pathosystem.

Keywords

Bromus tectorumpathosystemPyrenophora semeniperdaseed germinationtemperaturetimewater potential
Type
Research Papers
Information
Seed Science Research , Volume 23 , Issue 1 , March 2013 , pp. 57 - 66
Copyright
Copyright © Cambridge University Press 2012

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