Mapping of the S. demissum late blight resistance gene R8 to a new locus on chromosome IX

Abstract

The use of resistant varieties is an important tool in the management of late blight, which threatens potato production worldwide. Clone MaR8 from the Mastenbroek differential set has strong resistance to Phytophthora infestans, the causal agent of late blight. The F1 progeny of a cross between the susceptible cultivar Concurrent and MaR8 were assessed for late blight resistance in field trials inoculated with an incompatible P. infestans isolate. A 1:1 segregation of resistance and susceptibility was observed, indicating that the resistance gene referred to as R8, is present in simplex in the tetraploid MaR8 clone. NBS profiling and successive marker sequence comparison to the potato and tomato genome draft sequences, suggested that the R8 gene is located on the long arm of chromosome IX and not on the short arm of chromosome XI as was suggested previously. Analysis of SSR, CAPS and SCAR markers confirmed that R8 was on the distal end of the long arm of chromosome IX. R gene cluster directed profiling markers CDPSw54 and CDPSw55 flanked the R8 gene at the distal end (1 cM). CDPTm21-1, CDPTm21-2 and CDPTm22 flanked the R8 gene on the proximal side (2 cM). An additional co-segregating marker (CDPHero3) was found, which will be useful for marker assisted breeding and map based cloning of R8.

Conditional QTL underlying resistance to late blight in a diploid potato population

“…R genes conferring resistance to late blight, Rpi-moc1a.k.a. Rpi-mcq1 (Smilde et al 2005), Rpi-vnt1.1 Pel et al 2009), Rpi-phu1 (Śliwka et al 2006, Rpi-dlc1 (Golas et al 2010) and R8 (Jo et al 2011) have been reported in a similar position as dPI09c on the long arm of chromosome 9 in potato relatives. In the published sequence of the potato (DM) genome, nine Rpi-vnt1-like genes are present in the superscaffold PGSC0003DMB000000339, which in addition to the Rpi-vnt1-like genes contains other NBS-LRRlike genes.…”

High-Resolution Mapping of Two Broad-Spectrum Late Blight Resistance Genes from Two Wild Species of the Solanum circaeifolium Group

“…N-like profiling was also successfully applied to map a late blight R gene from Solanum avilesii (Rpi-avl1; Verzaux et al 2011) and from Solanum edinense (Rpi-edn3; Verzaux 2010). Variants of the CDP technique were recently used to specifically tag R gene homologs from Tm-2 2 , Sw5, Hero, and R2 gene clusters, for the mapping of the R8 late blight resistance gene from Solanum demissum (Jo et al 2011). The current study clearly shows that CDP profiling is not only suitable for mapping but also for fine mapping of R genes.…”

Transformation of the potato variety Desiree with single or multiple resistance genes increases resistance to late blight under field conditions

“…Late blight field trials were generally conducted as described previously by inoculation with P. infestans isolate IPO-C which was avirulent towards plants carrying the Rpisto1 and Rpi-vnt1.1, but virulent towards Rpi-blb3 containing plants. (Jo et al, 2011). Twelve plants per genotype (reference varieties and GM events), were divided over two plots of six plants, which were planted in a 3 Â 2 design over three rows.…”

“…Due to the very humid spring and early summer, late blight infection occurred spontaneously in the field and no inoculum was applied. The trial in the Netherlands in both seasons was inoculated on 1 st July as described previously by Jo et al (2011) and irrigated daily by overhead sprinklers to ensure successful disease development.…”