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Abstract Detail

Mycological Section

Beckstead, Julie [1], Ishizuka, Toby [1], McEvoy, Kelsey [1], Meyer, Susan E. [2].

Pathogen-caused seed mortality among a suite of annual weeds is influenced by seed dormancy and inoculum load but not host specificity.

Seed pathogens are important contributors to disease-related mortality in plant populations. In this study, we focus on the naturally-occurring fungal seed pathogen Pyrenophora semeniperda, which has been found primarily in the seed banks of the invasive Bromus tectorum (cheatgrass) in semi-arid grasslands. Pyrenophora semeniperda is a generalist that infects seeds of multiple grass hosts. We investigated P. semeniperda’s relationship with a suite of invasive annual grasses that are important in semi-arid shrublands: B. tectorum, Bromus diandrus, Bromus rubens, Bromus arvensis, and Taeniatherum caput-medusae. First, we investigated whether seed dormancy status and inoculum load impacted infection and pathogen-caused mortality on these five weeds. We found that pathogen populations on three host species (B. rubens, B diandrus, and T. caput-medusae) followed a pattern similar to those on B. tectorum in that recently harvested (dormant) seeds were killed (>80%), while nondormant seeds experienced high infection but very low mortality (< 1%). The exception was B. arvensis, which as a population exhibited low primary dormancy, so that even recently harvested seeds were largely able to escape death. All species experienced greater infection and mortality at higher inoculum loads. Next, we performed cross-inoculations to examine whether any level of host specialization exists. Although the pathogen populations and strains varied in virulence and host populations and lines varied in susceptibility, we found no strong evidence of host specialization (i.e., higher pathogen-caused mortality on the host of origin than on novel host). Collectively, these findings do not support the hypothesis that P. semeniperda has evolved host specialization on particular hosts species. Instead, these pathogen strains are able to infect and kill multiple annual grass species. Host seed dormancy level, differential host susceptibility, differential strain virulence, and inoculum loads are factors that determine the level of mortality a grass species may experience from this seed pathogen.

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1 - Gonzaga University, Department Of Biology, 502 E. Boone Avenue, Spokane, WA, 99258, USA

fungal plant pathogen
plant pathogen interactions
host specificity
Pyrenophora semeniperda
Seed germination.

Presentation Type: Oral Paper:Papers for Sections
Session: 36
Location: Cottonwoods North/Boise Centre
Date: Wednesday, July 30th, 2014
Time: 9:00 AM
Number: 36003
Abstract ID:315
Candidate for Awards:None

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