Development of High-Throughput Markers for Phytophthora Crown Rot Resistance in Strawberry

Phytophthora crown rot (PhCR) caused by Phytophthora cactorum is a common and destructive disease in cultivated strawberry (2n=8×=56) worldwide.  Cultivars range from highly susceptible to highly resistant and genetic resistance is the most effective way to control PhCR in commercial production.  In the previous study, a major quantitative trait locus (QTL) for PhCR resistance, Pc1, located on the distal end of linkage group 7D was discovered using whole-genome single nucleotide polymorphism (SNP) genotyping (IStraw90 Axiom^® SNP Array) and pedigree-based marker-trait association analysis (FlexQTL™) in complex, multi-family populations. Approximately 1.5 Mb region of Pc1 was determined for further sequence based on Axiom^® probe alignment to the Fragaria vesca ssp. bracteata reference genome (v2.0).  To identify molecular markers tightly linked to Pc1, SNP-based high resolution melting (HRM) and simple sequence repeat (SSR) markers were developed and tested for 8 cultivars and 15 advanced selections that inherited putative functional allele combinations of Pc1pc1 (heterozygous resistant) or pc1pc1 (susceptible) based on SNP haplotypes from the QTL analysis.  Markers segregating with the Pc1 allele will be utilized for fine mapping in larger, segregating F1 populations.  The most informative markers will be implemented in marker-assisted seedling selection to increase genetic gains for this trait in the University of Florida breeding program.