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

In the past, numerous Cf genes have been reported in tomato (Lycopersicon esculentum Mill.) that confer resistance against leaf mould (Cladosporium fulvum Cke.). We are interested in genetic variation at Cf loci. Therefore, previously uncharacterized Cf genes were further analysed. Recognition of the AVR4 elicitor, DNA gel blot analysis, PCR analysis and sequencing of part 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 reasons for discrepancies with earlier reports are discussed.