| dc.description.abstract | The necrotrophic fungus Parastagonospora nodorum (teleomorph; Phaeosphaeria
nodorum), is the causal agent of Septoria nodorum blotch (SNB) on common wheat (Triticum
aestivum L.) and durum wheat (Triticum turgidum L.). SNB is a serious foliar and glume disease
which causes significant yield losses in major wheat growing areas and has serious impact on
grain quality. P. nodorum produces necrotrophic effectors (NEs) that are recognized by and
interact with dominant host sensitivity genes in an inverse gene-for-gene manner. The NE-host
interaction is critical to induce necrotrophic effector-triggered susceptibility (NETS), resulting in
SNB disease. To date, nine NE-host sensitivity gene interactions, following a NETS model, have
been identified in the P. nodorum-wheat pathosystem. One of the NE-host sensitivity gene
interactions, SnTox6-Snn6 interaction was characterized in this study. The SnTox6-Snn6
interaction was shown to be light dependent and Snn6 was located to a major disease
susceptibility QTL on wheat chromosome 6A. SnTox1, another NE first identified in our lab,
interacts with the corresponding wheat sensitivity gene Snn1. SnTox1 was further characterized
in this study. The SnTox1 protein harbors C-terminal domains with a high degree of structural
homology to plant chitin binding proteins and was subsequently shown to bind chitin, a main
component of the fungal cell wall. Therefore, SnTox1 was hypothesized to compete with wheat
chitinases to bind chitin, preventing fungal cell wall degradation. To investigate this hypothesis,
the SnTox1 binding affinity with chitin was tested, as well as its potential function in the
protection against chitinases during fungal mycelial growth. To identify additional NE regions,
genome wide association study (GWAS) technology was used. A global collection of 191 P.
nodorum isolates were genotyped using a restriction-site associated DNA genotyping by
sequencing (RAD-GBS) protocol to identify SNP markers. Phenotypic data including fungal
inoculations and culture filtrate infiltrations were collected using 191 P. nodorum isolates across
several wheat lines. GWAS analyses were performed by regressing the phenotypic data and
genotypic data by running multiple GWAS models. | en_US |
