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United States Department of Agriculture

Agricultural Research Service

Research Project: HOST-PATHOGEN INTERACTIONS IN BARLEY AND WHEAT

Location: Cereal Crops Research

Title: Global diversity and distribution of three necrotrophic effectors in Phaeosphaeria nodorum and related species

Authors
item Mcdonald, Megan -
item Oliver, Richard -
item Friesen, Timothy
item Brunner, Patrick -
item Mcdonald, Bruce -

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 27, 2013
Publication Date: July 1, 2013
Repository URL: http://handle.nal.usda.gov/10113/57870
Citation: McDonald, M.C., Oliver, R.P., Friesen, T.L., Brunner, P.C., McDonald, B.A. 2013. Global diversity and distribution of three necrotrophic effectors in Phaeosphaeria nodorum and related species. New Phytologist. 199:241-251.

Interpretive Summary: Phaeosphaeria nodorum is a necrotrophic pathogen of wheat throughout the world. This pathogen produces several necrotrophic effectors (synonym host-selective toxin) that the pathogen uses to induce disease and gain nutrients from plant cells. Population genetic and phylogenetic studies showed that P. nodorum is a member of a species-complex that likely shares its center of origin with wheat. We examined the evolutionary history of three known necrotrophic effectors (NEs) produced by Phaeosphaeria nodorum (SnToxA, SnTox1, SnTox3). We screened over 1000 individuals for the presence/absence of each effector. Diversity at each NE locus was assessed by sequencing about 200 individuals. Based on this research, we propose that the frequency differences in each NE gene is based on the presence of the corresponding wheat sensitivity/susceptibility gene. The population harboring the highest sequence diversity was different for each effector locus and never coincided with populations harboring the highest diversity at neutral loci. Nine closely related Phaeosphaeria spp. were evaluated for the presence of each NE and only two of the nine species were found to harbor NEs. We present evidence that the three described NEs of P. nodorum were transmitted to its sister species, Phaeosphaeria avenaria tritici 1, via interspecific hybridization.

Technical Abstract: Population genetic and phylogenetic studies showed that P. nodorum is a member of a species-complex that likely shares its center of origin with wheat. We examined the evolutionary history of three known necrotrophic effectors (NEs) produced by Phaeosphaeria nodorum and compared it to neutral loci. We screened over 1000 individuals for the presence/absence of each effector and assigned each individual to a multi-effector genotype. Diversity at each NE locus was assessed by sequencing about 200 individuals. We found significant differences in effector frequency among populations. We propose that these differences reflect the presence/absence of the corresponding susceptibility gene in wheat cultivars. The population harboring the highest sequence diversity was different for each effector locus and never coincided with populations harboring the highest diversity at neutral loci. Coalescent and phylogenetic analyses show a discontinuous presence of all three NEs among nine closely related Phaeosphaeria spp. Only two of the nine species were found to harbor NEs. We present evidence that the three described NEs of P. nodorum were transmitted to its sister species, Phaeosphaeria avenaria tritici 1, via interspecific hybridization.

Last Modified: 9/21/2014
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