A tetraploid potato population was mapped for internal heat necrosis (IHN) using the Infinium 8303 potato SNP array, and QTL for IHN were identified on chromosomes 1, 5, 9 and 12 that explained 28.21% of the variation for incidence and 25.3% of the variation for severity. This research represents a significant step forward in our understanding of IHN, and sets the stage for future research focused on testing the utility of these markers in additional breeding populations. Internal heat necrosis (IHN) is a significant non-pathogenic disorder of potato tubers and previous studies have identified AFLP markers linked to IHN susceptibility in the tetraploid, B2721 potato mapping population. B2721 consists of an IHN susceptible×resistant cross: Atlantic×B1829-5. We developed a next-generation SNP-based linkage map of this cross using the Infinium 8303 SNP array and conducted additional QTL analyses of IHN susceptibility in the B2721 population. Using SNP dosage sensitive markers, linkage maps for both parents were simultaneously analyzed. The linkage map contained 3427 SNPs and totaled 1397.68 cM. QTL were detected for IHN on chromosomes 1, 5, 9, and 12 using LOD permutation thresholds and colocation of high LOD scores across multiple years. Genetic effects were modeled for each putative QTL. Markers associated with a QTL were regressed in models of effects for IHN incidence and severity for all years. In the full model, the SNP markers were shown to have significant effects for IHN (p < 0.0001), and explained 28.21% of the variation for incidence and 25.3% of the variation for severity. We were able to utilize SNP dosage information to identify and model the effects of putative QTL, and identify SNP loci associated with IHN resistance that need to be confirmed. This research represents a significant step forward in our understanding of IHN, and sets the stage for future research focused on testing the utility of these markers in additional breeding populations.

There are many challenges involved with the genetic analyses of autopolyploid species, such as the tetraploid potato, Solanum tuberosum (2n=4x=48). The development of new analytical methods has made it valuable to re-analyze an F1 population (n=156) derived from a cross involving 'Atlantic', a widely grown chipping variety in the USA. A fully integrated genetic map with 4,285 single nucleotide polymorphisms, spanning 1,630 cM, was constructed with MAPpoly software. We observed that bivalent configurations were the most abundant ones (51.0~72.4% depending on parent and linkage group), though multivalent configurations were also observed (2.2~39.2%). Seven traits were evaluated over four years (2006-8 and 2014) and quantitative trait loci (QTL) mapping was carried out using QTLpoly software. We detected 21 QTL for 15 out of 27 trait-year combination phenotypes. A hotspot on linkage group 5 was identified as QTL for maturity, plant yield, specific gravity and internal heat necrosis resistance over different years were co-located. We found over 500 genes around QTL peaks, including those on chromosome 5 that have been previously implicated in maturity (StCDF1) and tuber formation (POTH1). These QTL regions can be investigated further in order to allow genomics-assisted breeding in tetraploid potato.

There are many challenges involved with the genetic analyses of autopolyploid species, such as the tetraploid potato, Solanum tuberosum (2n = 4x = 48). The development of new analytical methods has made it valuable to re-analyze an F1 population (n = 156) derived from a cross involving ‘Atlantic’, a widely grown chipping variety in the USA. A fully integrated genetic map with 4285 single nucleotide polymorphisms, spanning 1630 cM, was constructed with MAPpoly software. We observed that bivalent configurations were the most abundant ones (51.0~72.4% depending on parent and linkage group), though multivalent configurations were also observed (2.2~39.2%). Seven traits were evaluated over four years (2006–8 and 2014) and quantitative trait loci (QTL) mapping was carried out using QTLpoly software. Based on a multiple-QTL model approach, we detected 21 QTL for 15 out of 27 trait-year combination phenotypes. A hotspot on linkage group 5 was identified with co-located QTL for maturity, plant yield, specific gravity, and internal heat necrosis resistance evaluated over different years. Additional QTL for specific gravity and dry matter were detected with maturity-corrected phenotypes. Among the genes around QTL peaks, we found those on chromosome 5 that have been previously implicated in maturity (StCDF1) and tuber formation (POTH1). These analyses have the potential to provide insights into the biology and breeding of tetraploid potato and other autopolyploid species.