Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.

Generalist plant pathogens may have wide host ranges, but many exhibit varying degrees of host specialization, with multiple pathogen races that have narrower host ranges. These races are often genetically distinct, with each race causing highest disease incidence on its host of origin. We examined...

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Main Authors: Julie Beckstead, Susan E Meyer, Toby S Ishizuka, Kelsey M McEvoy, Craig E Coleman
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2016-01-01
Series:PLoS ONE
Online Access:http://europepmc.org/articles/PMC4780786?pdf=render
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spelling doaj-dfc8103e0459424ba07a64c63e24ddf12020-11-24T21:35:15ZengPublic Library of Science (PLoS)PLoS ONE1932-62032016-01-01113e015105810.1371/journal.pone.0151058Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.Julie BecksteadSusan E MeyerToby S IshizukaKelsey M McEvoyCraig E ColemanGeneralist plant pathogens may have wide host ranges, but many exhibit varying degrees of host specialization, with multiple pathogen races that have narrower host ranges. These races are often genetically distinct, with each race causing highest disease incidence on its host of origin. We examined host specialization in the seed pathogen Pyrenophora semeniperda by reciprocally inoculating pathogen strains from Bromus tectorum and from four other winter annual grass weeds (Bromus diandrus, Bromus rubens, Bromus arvensis and Taeniatherum caput-medusae) onto dormant seeds of B. tectorum and each alternate host. We found that host species varied in resistance and pathogen strains varied in aggressiveness, but there was no evidence for host specialization. Most variation in aggressiveness was among strains within populations and was expressed similarly on both hosts, resulting in a positive correlation between strain-level disease incidence on B. tectorum and on the alternate host. In spite of this lack of host specialization, we detected weak but significant population genetic structure as a function of host species using two neutral marker systems that yielded similar results. This genetic structure is most likely due to founder effects, as the pathogen is known to be dispersed with host seeds. All host species were highly susceptible to their own pathogen races. Tolerance to infection (i.e., the ability to germinate even when infected and thereby avoid seed mortality) increased as a function of seed germination rate, which in turn increased as dormancy was lost. Pyrenophora semeniperda apparently does not require host specialization to fully exploit these winter annual grass species, which share many life history features that make them ideal hosts for this pathogen.http://europepmc.org/articles/PMC4780786?pdf=render
collection DOAJ
language English
format Article
sources DOAJ
author Julie Beckstead
Susan E Meyer
Toby S Ishizuka
Kelsey M McEvoy
Craig E Coleman
spellingShingle Julie Beckstead
Susan E Meyer
Toby S Ishizuka
Kelsey M McEvoy
Craig E Coleman
Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
PLoS ONE
author_facet Julie Beckstead
Susan E Meyer
Toby S Ishizuka
Kelsey M McEvoy
Craig E Coleman
author_sort Julie Beckstead
title Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
title_short Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
title_full Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
title_fullStr Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
title_full_unstemmed Lack of Host Specialization on Winter Annual Grasses in the Fungal Seed Bank Pathogen Pyrenophora semeniperda.
title_sort lack of host specialization on winter annual grasses in the fungal seed bank pathogen pyrenophora semeniperda.
publisher Public Library of Science (PLoS)
series PLoS ONE
issn 1932-6203
publishDate 2016-01-01
description Generalist plant pathogens may have wide host ranges, but many exhibit varying degrees of host specialization, with multiple pathogen races that have narrower host ranges. These races are often genetically distinct, with each race causing highest disease incidence on its host of origin. We examined host specialization in the seed pathogen Pyrenophora semeniperda by reciprocally inoculating pathogen strains from Bromus tectorum and from four other winter annual grass weeds (Bromus diandrus, Bromus rubens, Bromus arvensis and Taeniatherum caput-medusae) onto dormant seeds of B. tectorum and each alternate host. We found that host species varied in resistance and pathogen strains varied in aggressiveness, but there was no evidence for host specialization. Most variation in aggressiveness was among strains within populations and was expressed similarly on both hosts, resulting in a positive correlation between strain-level disease incidence on B. tectorum and on the alternate host. In spite of this lack of host specialization, we detected weak but significant population genetic structure as a function of host species using two neutral marker systems that yielded similar results. This genetic structure is most likely due to founder effects, as the pathogen is known to be dispersed with host seeds. All host species were highly susceptible to their own pathogen races. Tolerance to infection (i.e., the ability to germinate even when infected and thereby avoid seed mortality) increased as a function of seed germination rate, which in turn increased as dormancy was lost. Pyrenophora semeniperda apparently does not require host specialization to fully exploit these winter annual grass species, which share many life history features that make them ideal hosts for this pathogen.
url http://europepmc.org/articles/PMC4780786?pdf=render
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