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Abstract:
Background
Plant pathogens
Plants are most important for our diet. One of the world wide most produced and consumed is
wheat. Plant pathogens come from different taxa. They can be fungi, oomycetes, bacteria or
nematodes. Because we grow crops in large monocultures to saturate our requirements, we have
to deal with the fast spread of pathogens due to the low genetic diversity in this monocultures. This
way widely used crop cultivars have been rendered susceptible like the wheat cultivar OBELISK
that we use in this experiment. To ensure our food supply we need to improve our understanding of
the complex interactions between plants and pathogens, so that we can find better ways to render
them armless.
Zymoseptoria tritici the object of this project is an ascomycota and an world wide spread pathogen
on wheat, which is responsible for a big part of the world wide wheat crop failures.
Lifestyles of plant pathogens
Plant pathogenes feed on nutrients from the plant tissue. There are different lifestyles of the
pathogens, as there are biotroph pathogens lice Blumeria graminis that hide from the recognition of
the plant(Pierre J.G.M. Wit 2009), so that they can colonize the infected tissue of the plant. There
they spread far and use the nutrients in the plant tissue.
Another lifestyle is the necrotrophic one. Here the pathogene tracks the nutrients from dead plant
cells. Therefore they kill the plant cell and secret cell-wall-digesting enzymes(Lo Presti et al. 2015).
Zymoseptoria tritici is considered to be an hemibiotrophic fungus(Haueisen et al. 2017), which
means that Z. tritici firstly grows as an biotroph pathogene and after it reached an certain size in
the plant tissue it undergoes an live style change to the necrotrophic phase where it actively
induces cell dead.
Pathogen Effectors
Plants developed a broad range of defence mechanisms to protect themselves against pathogens,
but even this multi-layered defence can be overcome by specialized pathogens. There are several
ways fungi pathogens hide from the plant immune system or even use it for their own profit. The
fungus is able to do so with the help of effectors. Effectors are small cysteine rich secreted proteins
that are secreted during infection. (Pierre J.G.M. Wit 2009)
The plant defends itself with the aid of a mechanism that is called Hypersensitive Response (HR)
which leads to the dead of the infected areas. This HR is triggered when a recognition Protein
short RP recognises a structure of the pathogene. This is called a PAMP-triggered immunity. In this
case an HR that leads to the dead of the infected tissue would help the necrotrophic pathogen.
