Genome-Wide Association Analysis of Common Scab Resistance and Expression Profiling of Tubers in Response to Thaxtomin A Treatment Underscore the Complexity of Common Scab Resistance in Tetraploid Potato

Common scab of potato caused by pathogenic Streptomyces species poses an economic burden to commercial potato cultivation. Despite decades of research, no molecular markers linked to this trait are currently available, making the development of scab resistant potato varieties inefficient. We evaluated common scab lesion type and tuber coverage in 198 individuals segregating for common scab resistance in replicated field trials with high natural disease pressure over two growing seasons. To identify genetic features associated with resistance, we genotyped the tetraploid (4x) population and parental lines (Kalkaska and Tundra) using the Illumina Infinium 8303 Potato Array and conducted genome-wide association analysis. Here, we report two significant single nucleotide polymorphism (SNP) markers on chromosome 1 associated with both scab traits in both years as well as a SNP marker on chromosome 2 associated with scab tuber coverage. Gene expression profiling of the parents of this population in response to Thaxtomin A treatment revealed differential expression of genes in tubers putatively involved in cell wall biosynthesis and hormone signaling.