evolutionary genomics of plant-pathogenic ascomycetes 2019 presentations/6...plant-pathogenic fungi:...
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Evolutionary Genomics of Plant-Pathogenic
AscomycetesJeremy Dettman
(Agriculture & Agri-Food Canada, Ottawa)
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• Largest and most diverse class of Ascomycetes
• Many plant pathogens:– Cochliobolus– Setosphaeria/Exserohilum– Pyrenophora– Stagonospora– Leptosphaeria– Alternaria– Mycosphaerella/Zymoseptoria/
Septoria– Dothistroma– Cladosporium
Dothideomycetes
Schoch et al. 2009
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• Characteristics:– Ascolocular development– Bitunicate asci– Darkly pigmented
Dothideomycetes
Photos from Ariyawansa et al 2014
Pyrenophora phaeocomes 200um
50um
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Background• Evolutionary genomics of microbes:
– Species recognition– Microbial adaptation– Molecular evolution– Signatures of positive selection– Antimicrobial resistance
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Current Research Interests• Associating genetic/genomic variation
with relevant phenotypes inplant-pathogenic fungi:– Biosystematics, diagnostics– Pathogenicity, virulence– Speciation, host shifts– Secondary metabolites, fungicide
resistance– Molecular evolution, selection
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Alternaria• Pathogen of wide range of hosts• Pre- and post-harvest• Leaf blotch/spot, fruit spot, early blight,
black rot, sooty mold, black point, kernel smudge, etc.
Alternaria alternata
E. McKenzie
UMN ExtensionUMN Extension
Canadian Grain Commission
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Alternaria• Produces mycotoxins:
– Altertoxin, alternariol/monomethyl ether, tenuazonic acid
– Strong potential for regulation
• Problem for Phytosanitary Certification• APHIS US Regulated Plant Pest = 6
species and Alternaria sp.
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Taxonomy and Diagnostics
Section Alternaria
Section Infectoriae
A. arborescens A. alternata
A. conjuncta A. oregonensis
Photos from Woudenberg et al 2013
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Mycotoxin Production
Extracted Compounds
Alte
rnar
ia s
train
s
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Mycotoxin Prediction• Is production strain- or species-specific?• Conditionally dispensable
chromosomes?• Methods to detect gene clusters?
Examples of polyketide synthases in A. alternata(Saha et al 2012)
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Northern Corn Leaf Blight• Exserohilum turcicum (Setosphaeria turcica)
• Greatest yield loss of any corn disease
L. Ramos-Romero
Jayasiri et al 2015
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Northern Corn Leaf BlightPathogen Race Resistance Gene in Corn
Ht1 Ht2 Ht3 Htm1 Htn10 – – – – –1 + – – – –12 + + – – –13M + – + + –13MN + – + + +123MN + + + + +“+” denotes host susceptibility to infection, “–” denotes resistance
OMAFRA
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Northern Corn Leaf Blight• What genetic/genomics differences
define the various NCLB races?– 11.7K genes - 77% with no polymorphisms
• Molecular assay for race determination?• Mechanisms of pathogenicity?• Hyper-virulent races?