The Solanum demissumR8 late blight resistance gene is an Sw-5 homologue that has been deployed worldwide in late blight resistant varieties
Sunday, 2016/09/04 | 06:53:40
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Jack H. Vossen, Gert van Arkel, Marjan Bergervoet, Kwang-Ryong Jo, Evert Jacobsen, Richard G. F. Visser AbstractKey messageThe potato late blight resistance geneR8has been cloned.R8is found in five late blight resistant varieties deployed in three different continents. R8 recognises Avr8 and is homologous to the NB-LRR protein Sw-5 from tomato. AbstractThe broad spectrum late blight resistance gene R8 from Solanum demissum was cloned based on a previously published coarse map position on the lower arm of chromosome IX. Fine mapping in a recombinant population and bacterial artificial chromosome (BAC) library screening resulted in a BAC contig spanning 170 kb of the R8 haplotype. Sequencing revealed a cluster of at least ten R gene analogues (RGAs). The seven RGAs in the genetic window were subcloned for complementation analysis. Only one RGA provided late blight resistance and caused recognition of Avr8. From these results, it was concluded that the newly cloned resistance gene was indeed R8. R8 encodes a typical intracellular immune receptor with an N-terminal coiled coil, a central nucleotide binding site and 13 C-terminal leucine rich repeats. Phylogenetic analysis of a set of representative Solanaceae R proteins shows that R8 resides in a clearly distinct clade together with the Sw-5 tospovirus R protein from tomato. It was found that the R8 gene is present in late blight resistant potato varieties from Europe (Sarpo Mira), USA (Jacqueline Lee, Missaukee) and China (PB-06, S-60). Indeed, when tested under field conditions, R8 transgenic potato plants showed broad spectrum resistance to the current late blight population in the Netherlands, similar to Sarpo Mira.
See: http://link.springer.com/article/10.1007/s00122-016-2740-0 Theoretical and Applied Genetics; September 2016, Volume 129, Issue 9, pp 1785–1796
Fig. 1 Genetic and physical map of R8 on the bottom end of chro-mosome 9. The upper part of this igure represents a genetic map. Markers of different origin were mapped in an F1 recombinant pop-ulation of 1670 individuals and their relative positions are indicated by vertical lines. The number of recombinants between the markers is indicated by numbers between the vertical lines. The orizontal line marked by R8 indicates the genetic mapping interval for R8. The lower part of this igure represents a physical map. Using molecu-lar markers, BAC clones were identiied from BAC libraries derived from MaR8. The grey bars represent the individual BAC clones. Ve r-tical lines indicate the connection between the physical and genetic maps. Arrows indicate the position and orientations of resistance gene analogues (RGA0.10-RGA3.3) on the physical map. RGA0.20 is the functional R8 gene. |
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