title: Diversity, distribution, and evolution of Solanum bulbocastanum late blight resistance genes.
abstract: Knowledge on the evolution and distribution of late blight resistance genes is important for a better understanding of the dynamics of these genes in nature. We analyzed the presence and allelic diversity of the late blight resistance genes Rpi-blb1, Rpi-blb2, and Rpi-blb3, originating from Solanum bulbocastanum, in a set of tuber-bearing Solanum species comprising 196 different taxa. The three genes were only present in some Mexican diploid as well as polyploid species closely related to S. bulbocastanum. Sequence analysis of the fragments obtained from the Rpi-blb1 and Rpi-blb3 genes suggests an evolution through recombinations and point mutations. For Rpi-blb2, only sequences identical to the cloned gene were found in S. bulbocastanum accessions, suggesting that it has emerged recently. The three resistance genes occurred in different combinations and frequencies in S. bulbocastanum accessions and their spread is confined to Central America. A selected set of genotypes was tested for their response to the avirulence effectors IPIO-2, Avr-blb2, and Pi-Avr2, which interact with Rpi-blb1, Rpi-blb2, and Rpi-blb3, respectively, as well as by disease assays with a diverse set of isolates. Using this approach, some accessions could be identified that contain novel, as yet unknown, late blight resistance factors in addition to the Rpi-blb1, Rpi-blb2, and Rpi-blb3 genes.
authors.affiliation: Wageningen UR Plant Breeding, P.O. Box 16, 6700AA, Wageningen, The Netherlands.
authors.forename: Anoma A
authors.initials: AA
authors.lastname: Lokossou
authors.forename: Hendrik
authors.initials: H
authors.lastname: Rietman
authors.forename: Miqia
authors.initials: M
authors.lastname: Wang
authors.forename: Pavel
authors.initials: P
authors.lastname: Krenek
authors.forename: Hanneke
authors.initials: H
authors.lastname: van der Schoot
authors.forename: Betty
authors.initials: B
authors.lastname: Henken
authors.forename: Roel
authors.initials: R
authors.lastname: Hoekstra
authors.forename: Vivianne G A A
authors.initials: VG
authors.lastname: Vleeshouwers
authors.forename: Edwin A G
authors.initials: EA
authors.lastname: van der Vossen
authors.forename: Richard G F
authors.initials: RG
authors.lastname: Visser
authors.forename: Evert
authors.initials: E
authors.lastname: Jacobsen
authors.forename: Ben
authors.initials: B
authors.lastname: Vosman
mesh_terms: D005075:Biological Evolution; D018744:DNA, Plant; D014644:Genetic Variation; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology; D016133:Polymerase Chain Reaction; D032322:Solanum / Q000382:microbiology*
chemical_list: D018744:DNA, Plant