High Density Linkage Mapping and Identification of Quantitative Trait Loci Associated with Powdery Mildew Resistance in Flowering Dogwood (Cornus florida)

We mapped quantitative trait loci (QTL) associated with PM resistance/tolerance in two full sibling populations segregating for PM response: Rutgers H4AR15P25 (P25) x Rutgers H4AR15R28 (P28) (n=195) and Rutgers H4AR15R25 x Rutgers H4AR15P35 (P35) (n=83). High density genetic linkage maps were constructed for the mapping populations using double digest restriction-site associated DNA sequencing-derived single nucleotide polymorphisms (SNPs) and simple sequence repeats (SSRs). The P25xP28 map consisted of 2265 markers, spanning 1,520 cM and 11 linkage groups (LGs) with an average marker spacing of 0.69 cM. The P25xP35 map was constructed with 1788 markers, spanning 1,256 cM and 11 LGs, with an average marker spacing of 0.72 cM. Through multiple QTL model mapping, one major QTL (LOD=11.36 and R^2=58.9%) was identified in P25xP35. Further, a minor QTL (LOD=3.30 and R^2=7.8%) was detected in P25xP28.