QTLs for Tomato Powdery Mildew Resistance (Oidium lycopersici) in Lycopersicon parviflorum G1.1601 Co-localize with Two Qualitative Powdery Mildew Resistance Genes

Abstract

Tomato (Lycopersicon esculentum) is susceptible to the powdery mildew Oidium lycopersici, but several wild relatives such as Lycopersicon parviflorum G1.1601 are completely resistant. An F2 population from a cross of Lycopersicon esculentum cv. Moneymaker x Lycopersicon parviflorum G1.1601 was used to map the O. lycopersici resistance by using amplified fragment length polymorphism markers. The resistance was controlled by three quantitative trait loci (QTLs). Ol-qtl1 is on chromosome 6 in the same region as the Ol-1 locus, which is involved in a hypersensitive resistance response to O. lycopersici. Ol-qtl2 and Ol-qtl3 are located on chromosome 12, separated by 25 cM, in the vicinity of the Lv locus conferring resistance to another powdery mildew species, Leveillula taurica. The three QTLs, jointly explaining 68% of the phenotypic variation, were confirmed by testing F3 progenies. A set of polymerase chain reaction-based cleaved amplified polymorphic sequence and sequence characterized amplified region markers was generated for efficient monitoring of the target QTL genomic regions in marker assisted selection. The possible relationship between genes underlying major and partial resistance for tomato powdery mildew is discussed.

Resistance gene analogues identified through the NBS-profiling method map close to major genes and QTL for disease resistance in apple

“…Speulman et al 1998;Geffroy et al 2000;Gebhardt and Valkonen 2001), and thus may provide either interesting candidate genes or useful markers for marker-assisted selection (MAS). They also provide information about the organization and evolution of resistance genes and RGAs in plant genomes (Grube et al 2000;Pan et al 2000;Bai et al 2003;Meyers et al 2003).…”

Genetics and molecular mechanisms of resistance to powdery mildews in tomato (Solanum lycopersicum) and its wild relatives

“…Silencing Mi-1 homologues in tomato lines carrying Ol-4 and Ol-6 compromised the resistance to O. neolycopersici in those lines, demonstrating that Ol-4 and Ol-6 are Mi-1 homologues . In addition to these monogenic resistance genes, three quantitative trait loci (Ol-qtls) were identified in S. neorickii G1.1601 (Bai et al 2003). Ol-qtl1 was mapped on chromosome 6 in a chromosomal region where Ol-1, Ol-3 and Ol-5 are located.…”

“…Ol-qtl1 was mapped on chromosome 6 in a chromosomal region where Ol-1, Ol-3 and Ol-5 are located. Ol-qtl2 and Ol-qtl3 were mapped on chromosome 12 in the vicinity of the Lv gene (Bai et al 2003). Ol-qtl1 and Ol-qtl2 were further finemapped using advanced populations, while the presence of Ol-qtl3 needs to be further confirmed ( Fig.…”

“…Interestingly, these three Ol-genes originate from different accessions of S. habrochaites and cluster together on the long arm of tomato chromosome 6 (Fig. 1) (Bai et al 2003). Since such type of HR occurs only in about 30 % of infected cells, fungal colonization is not prevented completely and thus leads to an incomplete resistance.…”

“…The recessive gene, ol-2, which is a homologue of the barley MLO gene, mediates resistance by formation of papillae, i.e., cell wall appositions of callose and other constituents at plant-PM interaction sites (Bai et al 2003. Papillae are formed before and/or immediately after the formation of primary haustoria, resulting in early stop of fungal growth and leading to a complete resistance.…”