The interaction between Lycopersicon esculentum and the biotrophic fungal pathogen Cladosporium fulvum is a model for studying the molecular basis of plantpathogen interactions. Cf genes confer resistance against specific races of the fungus through recognition of proteins encoded by fungal avirulence (Avr) genes. Cf genes present in the near-isogenic lines Cf2, Cf4, Cf5 and Cf9 have been shown to encode Type I extracellular leucine-rich repeat (LRR) glycoproteins anchored in the plasma membrane. The objective of this research was to isolate and characterise a novel locus for resistance to C. fulvum. The Cf1l line contains one characterised Cf gene (Cf-4), and one other gene that was designated Cf-11. Previous reports indicated Cf- 11 may represent a novel resistance specificity. Results presented in this thesis demonstrate that Cf-11 is unlinked to known Cf gene loci, and thus represents a new locus in tomato for resistance to C. fulvum. Markers linked in cis and in trans to Cf- 11 were identified by AFLP analysis of various bulked segregant pools. Cf-11 was mapped to an interval on chromosome l1 close to the reported map location of Cf-3. A high-resolution genetic map of the target locus was constructed to facilitate cloning of Cf-I1, and eventually, to provide further insight into the tomato-C. fulvum interaction. To test the hypothesis that Cf-11 and Cf-3 might form part of a complex locus, differences in their resistance specificities were investigated using different C. fislvum races, but these analyses proved inconclusive. However, a detailed analysis of the resistance to C. fulvum race 4 infection revealed clear differences between Cf- 3 and Cf-11, consistent with the hypothesis that they represent distinct resistance genes. Cf-11 arose in a breeding experiment in 1972 but its precise origin is not known. The low level of DNA sequence polymorphism between Cf1l and Cif lines suggests Cf-11 arose from an L. esculentum variety, and possibly a line that contained Cf-3.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:426440 |
| Date | January 2005 |
| Creators | Anderson, Elizabeth |
| Publisher | University of East Anglia |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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