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Resistance in winter barley against Ramularia leaf spot

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Rasmus Lund Hjortshøj, Danmark
Ramularia leaf spot is an emerging disease in barley caused by R. collo-cygni. At present little is known about the resistance mechanisms carried out by the host plant to avoid disease development. Nor is the lifecycle of the fungus or its populations structure fully understood.
To gain insight into these aspects four experiments were set up; (1) a mapping experiment aiming at identifying QTL’s controlling disease levels under field conditions was conducted in two winterbarley populations. (2) a toxin assay testing the parental lines used in the mapping populations for response to Rubellin D was developed. (3) microarray analysis of transcriptional response in barley to inoculation with R. collo-cygni was carried out, and finally the (4) population genetic structure of R. collo-cygni was assessed by AFLP and gene sequencing.
Based on these experiments interaction was compared to the interactions of C. fulvum-tomato and S. tritici-wheat in order to find modelsystems to enhance interpretation of results from R. collo-cygni-barley interaction.
Results from the mapping showed that resistance to Ramularia leaf spot is controlled by a number of QTL’s, some of which co-locate with other physiological traits. The populations further segregated for physiological leaf spots, a phenomenon related to the leaf damage imposed by Rubellin, although, resistance to physiological leafspots appeared to come from the Ramularia leaf spot susceptible parent. The toxin assay further supported this result as the genotypes susceptible to physiological leaf spots also had much more severe reaction to the toxin. In the microarray experiment the first timepoint revealed large differences in transcriptional response related to defence responses The later timepoint was more even in transcriptional response, with an apparent shift towards abiotic stress responses. Finally the population genetic study based on low distances between populations samples in Denmark and Scotland and high genotypic diversity gave indications of a pathogen with a high evolutionary potential.
Altogether, this points to a plant-pathogen system resembling that of S. tritici in wheat.
The implications of this is further discussed in the thesis.
OriginalsprogEngelsk
UdgivelsesstedAarhus University
ForlagAarhus University, Faculty of Science and Technology
Antal sider139
StatusUdgivet - 28 feb. 2012

    Forskningsområder

  • sygdoms resistens, mapping, Disease resistance, Ramularia leaf spot (RLS), ramularia collo-cygni, Microarray, toxin, plant breeding

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