Identification and analysis of mechanisms involved in a broad-spectrum disease resistant mutant of the winter wheat cv. Guardian

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dc.contributor.advisor Jones, Peter W. en Hehir, Gerard 2015-10-23T11:47:01Z 2014 2014
dc.identifier.citation Hehir, G. 2014. Identification and analysis of mechanisms involved in a broad-spectrum disease resistant mutant of the winter wheat cv. Guardian. PhD Thesis, University College Cork. en
dc.description.abstract M66 an X-ray induced mutant of winter wheat (Triticum aestivum) cv. Guardian exhibits broad-spectrum resistance to powdery mildew (Blumeria graminis f. sp. tritici), yellow rust (Puccinia striiformis f. sp. tritici), and leaf rust (Puccinia recondita f. sp. tritici), along with partial resistance to stagnonospora nodorum blotch (caused by the necrotroph Stagonosporum nodorum) and septoria tritici blotch (caused by the hemibiotroph Mycosphaerella graminicola) compared to the parent plant ‘Guardian’. Analysis revealed that M66 exhibited no symptoms of infection following artificial inoculation with Bgt in the glasshouse after adult growth stage (GS 45). Resistance in M66 was associated with widespread leaf flecking which developed during tillering. Flecking also occurred in M66 leaves without Bgt challenge; as a result grain yields were reduced by approximately 17% compared to ‘Guardian’ in the absence of disease. At the seedling stage, M66 exhibited partial resistance. M66, along with Tht mutants (Tht 12, Tht13), also exhibit increased tolerance to environmental stresses (abiotic), such as drought and heat stress at seedling and adult growth stages, However, adult M66 exhibited increased susceptibility to the aphid Schizaphis graminum compared to ‘Guardian’. Resistance to Bgt in M66 was characterized with increased and earlier H2O2 accumulation at the site of infection which resulted in increased papilla formation in epidermal cells, compared to ‘Guardian’. Papilla formation was associated with reduced pathogen ingress and haustorium formation, indicating that the primary cause of resistance in M66 was prevention of pathogen penetration. Heat treatment at 46º C prior to challenge with Bgt also induced partial disease resistance to Blumeria graminis f. sp. tritici in ‘Guardian’ and M66 seedlings. This was characterized by a delay in primary infection, due to increased production of ROS species, such as hydrogen peroxide, ROS-scavenging enzymes and Hsp70, resulting in cross-linking of cell wall components prior to inoculation. This actively prevented the fungus from penetrating the epidermal cell wall. Proteomics analysis using 2-D gel electrophoresis identified primary and secondary disease resistance effects in M66 including detection of ROS scavenging enzymes (4, 24 hai), such as ascorbate peroxidase and a superoxidase dismutase isoform (CuZnSOD) in M66 which were absent from ‘Guardian’. Chitinase (PR protein) was also upregulated (24 hai) in M66 compared to ‘Guardian’.Monosomic and ditelosomic analysis of M66 revealed that the mutation in M66 is located on the long arm of chromosome 2B (2BL). Chromosome 2BL is known to have key genes involved in resistance to pathogens such as those causing stripe rust and powdery mildew. The TaMloB1 gene, an orthologue of the barley Mlo gene, is also located on chromosome 2BL. Sanger sequencing of part of the coding sequence revealed no deletions in the TaMloB1 gene between ‘Guardian’ and M66. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher University College Cork en
dc.rights © 2014, Gerard Hehir. en
dc.rights.uri en
dc.subject m66 en
dc.subject Broad-spectrum en
dc.subject Wheat en
dc.subject Disease en
dc.title Identification and analysis of mechanisms involved in a broad-spectrum disease resistant mutant of the winter wheat cv. Guardian en
dc.type Doctoral thesis en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD (Science) en
dc.internal.availability Full text not available en Indefinite en 10000-01-01
dc.description.version Accepted Version
dc.description.status Not peer reviewed en Biological, Earth & Environmental Sciences en
dc.check.reason This thesis is due for publication or the author is actively seeking to publish this material en
dc.check.opt-out Yes en
dc.thesis.opt-out true
dc.check.entireThesis Entire Thesis Restricted
dc.check.embargoformat Hard bound copy in Library only en
dc.internal.conferring Spring Conferring 2015

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© 2014, Gerard Hehir. Except where otherwise noted, this item's license is described as © 2014, Gerard Hehir.
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