DNA amplification fingerprinting and marker screening for pseudo-testcross mapping of flowering dogwood (Cornus florida L.)

DNA amplification fingerprinting (DAF) with arbitrary oligonucleotide primers was used to study genetic relationships between cultivars of flowering dogwood (Cornus florida L.), evaluate extent of plant hybridization, and generate markers in pseudo-testcross mapping at the intraspecific level. Modified Taguchi optimization methods defined a robust DAF system based on high annealing temperature (48-52 °C) and primer concentration (typically 8 μM) that was used to study genetic diversity of representative dogwood cultivars and hybrids. Phenetic analysis using cluster and numerical methods showed that: (1) cultivars were relatively conserved at the genetic level; (2) their hybridization could be identified in the F₁ progeny in the absence of phenotypic or physiological markers; (3) several cultivars grouped according to their recorded ancestry; and (4) dogwood anthracnose-resistant lines originally selected in Catoctin Mountain Park (Maryland) grouped separately from those of southern origin. The DAF protocol was also tested in pseudo-testcross mapping of dogwood at the intraspecific level. A preliminary screening of parents 'Pink Sachet' and 'Fragrant Cloud' and 7 F₁ segregants with 22 octamer primers produced 703 amplified loci, 30 and 39 of which were male and female markers segregating at 1:1 ratios with 98.6% confidence levels in pseudo-testcross configuration. Overall results show that DAF generated markers very efficiently (3 per primer) despite the close relatedness of parental dogwood cultivars. This study constitutes the basis for a future genetic linkage mapping and marker-assisted selection (MAS) effort initially targeted to control important fungal diseases in dogwood.