title: A second gene at the tomato Cf-4 locus confers resistance to cladosporium fulvum through recognition of a novel avirulence determinant
abstract: The tomato Cf-4 and Cf-9 genes confer resistance to the leaf mould pathogen Cladosporium fulvum and map at a complex locus on the short arm of chromosome 1. It was previously shown that the gene encoding Cf-4, which recognizes the Avr4 avirulence determinant, is one of five tandemly duplicated homologous genes (Hcr9-4s) at this locus. Cf-4 was identified by molecular analysis of rare Cf-4/Cf-9 disease-sensitive recombinants and by complementation analysis. The analysis did not exclude the possibility that an additional gene(s) located distal to Cf-4 may also confer resistance to C. fulvum. We demonstrate that a number of Dissociation-tagged Cf-4 mutants, identified on the basis of their insensitivity to Avr4, are still resistant to infection by C. fulvum race 5. Molecular analysis of 16 Cf-4 mutants, most of which have small chromosomal deletions in this region, suggested the additional resistance specificity is encoded by Hcr9-4E. Hcr9-4E recognizes a novel C. fulvum avirulence determinant that we have designated Avr4E.
authors.initials: FL
authors.lastname: Takken
authors.initials: CM
authors.lastname: Thomas
authors.initials: MH
authors.lastname: Joosten
authors.initials: C
authors.lastname: Golstein
authors.initials: N
authors.lastname: Westerink
authors.initials: J
authors.lastname: Hille
authors.initials: HJ
authors.lastname: Nijkamp
authors.lastname: De Wit PJ
authors.initials: JD
authors.lastname: Jones