Interval Mapping of Quantitative Trait Loci for Corky Ringspot Disease Resistance in a Tetraploid Population of Potato (Solanum tuberosum subsp. tuberosum)

Corky ringspot disease (CRS) resistance is an ideal target trait for breeding using marker-assisted selection (MAS) due to the high variability in field disease incidence that complicates screening for resistance. To develop molecular marker(s) associated with CRS resistance, a linkage map was constructed for a tetraploid population of 92 genotypes in order to conduct quantitative trait locus (QTL) analysis. The population was tested for CRS resistance in an infested screening field for four years. Broad sense heritability and its standard error of CRS disease resistance were 0.80 (±0.16). A total of 892 AFLP, 95 SSR, and 5 SSCP markers were scored and used for testing marker-trait association. One major QTL that explained 43% of the phenotypic variation in CRS resistance was localized on chromosome IX, with flanking AFLP markers AAC-CGT-0347 and ACG-CTG-0588. A minor QTL that explained 12% of CRS resistance was also detected. This minor QTL was associated with distorted marker GGT-CAC-0259, which remained unlinked. Polygenetic nature of CRS resistance was explained by major and minor QTLs association. Conversion of the three AFLP markers associated with this quantitative trait to simple PCR markers will benefit resistance breeding by enabling MAS.