title: An ancient R gene from the wild potato species Solanum bulbocastanum confers broad-spectrum resistance to Phytophthora infestans in cultivated potato and tomato.
abstract: Late blight, caused by the oomycete pathogen Phytophthora infestans, is the most devastating disease for potato cultivation. Here, we describe the positional cloning of the Rpi-blb1 gene from the wild potato species Solanum bulbocastanum known for its high levels of resistance to late blight. The Rpi-blb1 locus, which confers full resistance to complex isolates of P. infestans and for which race specificity has not yet been demonstrated, was mapped in an intraspecific S. bulbocastanum population on chromosome 8, 0.3 cM from marker CT88. Molecular analysis of a bacterial artificial chromosome (BAC) clone spanning the Rpi-blb1 locus identified a cluster of four candidate resistance gene analogues of the coiled coil, nucleotide-binding site, leucine-rich repeat (CC-NBS-LRR) class of plant resistance (R) genes. One of these candidate genes, designated the Rpi-blb1 gene, was able to complement the susceptible phenotype in a S. tuberosum and tomato background, demonstrating the potential of interspecific transfer of broad-spectrum late blight resistance to cultivated Solanaceae from sexually incompatible host species. Paired comparisons of synonymous and non-synonymous nucleotide substitutions between different regions of Rpi-blb1 paralogues revealed high levels of synonymous divergence, also in the LRR region. Although amino acid diversity between Rpi-blb1 homologues is centred on the putative solvent exposed residues of the LRRs, the majority of nucleotide differences in this region have not resulted in an amino acid change, suggesting conservation of function. These data suggest that Rpi-blb1 is relatively old and may be subject to balancing selection.
authors.affiliation: Plant Research International BV, PO Box 16, 6700 AA Wageningen, the Netherlands. edwin.vandervossen@wur.nl
authors.forename: Edwin
authors.initials: E
authors.lastname: van der Vossen
authors.forename: Anne
authors.initials: A
authors.lastname: Sikkema
authors.forename: Bas te Lintel
authors.initials: Bt
authors.lastname: Hekkert
authors.forename: Jack
authors.initials: J
authors.lastname: Gros
authors.forename: Patricia
authors.initials: P
authors.lastname: Stevens
authors.forename: Marielle
authors.initials: M
authors.lastname: Muskens
authors.forename: Doret
authors.initials: D
authors.lastname: Wouters
authors.forename: Andy
authors.initials: A
authors.lastname: Pereira
authors.forename: Willem
authors.initials: W
authors.lastname: Stiekema
authors.forename: Sjefke
authors.initials: S
authors.lastname: Allefs
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D022202:Chromosomes, Artificial, Bacterial; D003001:Cloning, Molecular; D016384:Consensus Sequence; D017931:DNA Primers; D015723:Gene Library; D017343:Genes, Plant; D007113:Immunity, Innate / Q000235:genetics*; D018551:Solanum lycopersicum / Q000235:genetics* / Q000382:microbiology; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000472:pathogenicity*; D010935:Plant Diseases; D030821:Plants, Genetically Modified / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019657:Solanaceae / Q000235:genetics* / Q000382:microbiology*; D011198:Solanum tuberosum / Q000235:genetics* / Q000382:microbiology
chemical_list: D017931:DNA Primers