Flowering dogwood (Cornus florida L.) is an important tree of forests and urban landscapes in the eastern United States. Currently, there are over 100 cultivars of flowering dogwood commercially available. An identification process based on genotype would be of use to researchers, breeders, and nurserymen, as many cultivars are similar phenotypically. Molecular markers offer a promising way of definitively identifying flowering dogwood cultivars. Amplified fragment length polymorphism (AFLP) is a technique that can be used to generate DNA fingerprints. DNA was isolated from leaves of 17 common cultivars of dogwood and AFLP fingerprints were generated by a Beckman Coulter CEQ™ 8000. Fingerprints were converted to binary data and verified manually. Two drafts of a cultivar identification key were generated based on the corrected, verified binary data and cultivar-specific peaks. Six primer combinations were used to construct all keys and were tested with seven unknown dogwood cultivar samples. Six unknown samples were correctly identified using the keys. Only one unknown, `Cherokee Brave', was unidentifiable with any key. In all cases, some intracultivar variation was observed. A similarity index was calculated and visualized with a tree of genetic relatedness using NTSYSpc. Intracultivar variation was observed in the similarity index as well. This database for cultivar-specific molecular markers will serve as a starting point to which other cultivars can be added and also can be used in breeding applications, patent application and other projects, such as mapping the C. florida genome.
Naomi R. Smith and Robert N. Trigiano
Naomi R. Smith, Robert N. Trigiano, Mark T. Windham, Kurt H. Lamour, Ledare S. Finley, Xinwang Wang, and Timothy A. Rinehart
Flowering dogwood (Cornus florida L.) is an important tree of forests and urban landscapes in the eastern United States. Amplified fragment length polymorphism (AFLP) markers were generated from genomic DNA of 17 cultivars and lines, and four duplicate samples of selective cultivars. Specific markers were identified for all except the following two lines and cultivar: MW94-67, MW95-12, and ‘Plena’. A dichotomous cultivar identification key was constructed based on AFLP data, and specific peaks or combinations of peaks were identified for all cultivars and lines. The key was assessed with seven anonymous (unlabeled) dogwood samples, and all unknowns except one were identified using the dichotomous key. Two of the unknown samples, ‘Cherokee Chief’ and ‘Cherokee Brave’, were difficult to distinguish using the AFLP markers. Intracultivar variation, up to 36% dissimilarity, was observed between duplicate samples of the same cultivar from different trees, suggesting that some mislabeling of trees had occurred at the nursery. The cultivar-specific AFLP markers can be used in breeding applications, patent protection, and in future projects, such as mapping the C. florida genome.