| dc.description.abstract | Black spot disease (Diplocarpon rosae (Lib.) Wolf) of rose is the most important
leaf disease of garden roses worldwide. Although partial (horizontal) resistance to black
spot has been shown to be moderately heritable, the responsible quantitative trait loci
(QTL) remain unidentified. The objective of this study was to generate thousands of
informative single nucleotide polymorphism (SNP) markers for genetic linkage and QTL
mapping.
Five highly black spot resistant breeding lines derived from R. wichuriana
‘Basye’s Thornless’, a moderately susceptible cultivar, and four highly susceptible
cultivars with excellent ornamental characteristics were used to generate fifteen diploid
populations (2n=2x=14) for this study. The disease severity of 812 field-grown seedlings
was assessed on the percentage of foliage covered with lesions (PFS) and the size of the
lesions (BLS) rating in June, September, October and November of 2016. Lesion size
rating was moderately correlated with the amount of foliage with lesions (r = 0.59). The
estimated narrow and broad sense heritability of partial resistance was 0.12-0.54 and
0.53, respectively for PFS, and 0.07-0.42 and 0.58, respectively for BLS indicating that
partial resistance to black spot is a moderately heritable trait.
By utilizing genotyping by sequencing (GBS) technology, we created a high-density
integrated consensus map for diploid roses (ICD) with thousands of informative
single nucleotide polymorphism (SNP) markers and known bridge single sequence
repeat (SSR) markers. 824 SNPs and 13 SSR bridge markers shared among three
individual maps of populations were used to link the three maps to generate the consensus map. As a result, the ICD is composed of 3527 molecular markers covering a
total length of 892.2 cM with an average distance between markers of 0.25 cM. The high
synteny between the strawberry and diploid rose genome was also clearly demonstrated.
One major black spot QTL on LG3 at interval 34-44 cM explaining ~20% of the total
phenotypic variance was consistently present in the June, September, October,
November and combined analyses. This approach serves as a model study for
performing pedigree-based analysis (PBA) on materials with a diverse genetic
background. The results will support downstream marker assisted breeding (MAB). | en |
