Dispersion of the Cf-4 disease resistance gene in Lycopersicon germplasm

In the past, numerous Cf genes have been reported in tomato (Lycopersicon e sculentum Mill.) that confer resistance against leaf mould (Cladosporium? f ulvum Cke.). We are interested in genetic variation at Cf loci. Therefore, previously uncharacterized Cf genes were further analysed. Recognition of t he AVR4 elicitor, DNA gel blot analysis, PCR analysis and sequencing of par t of the Cf-4 locus showed that a large proportion of the accessions tested harboured the Cf-4 resistance gene. We concluded that despite differences in nomenclature, all these accessions harbour the same Cf-4 locus, probably introgressed from the same donor. The origin of the Cf-4 locus and the rea sons for discrepancies with earlier reports are discussed.