Evaluating the relationship between diploid and tetraploid Vaccinium oxycoccos (Ericaceae) in eastern Canada

Authors: SMITH, TYLER - Agriculture And Agri-Food Canada; WALINGA, CHARLOTTE - University Of Ottawa; WANG, SONG - Agriculture And Agri-Food Canada; KRON, PAUL - University Of Guelph; SUDA, JAN - Charles University, Czech Republic; Zalapa, Juan

Submitted to: Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2015
Publication Date: 6/10/2015
Publication URL: http://handle.nal.usda.gov/10113/61574
Citation: Smith, T.W., Walinga, C., Wang, S., Kron, P., Suda, J., Zalapa, J. 2015. Evaluating the relationship between diploid and tetraploid Vaccinium oxycoccos (Ericaceae) in eastern Canada. Botany. 93(10):623-636. doi: 10.1139/cjb-2014-0223.

Interpretive Summary: The small cranberry is a trailing, evergreen vine of peatlands, most commonly growing partially buried by living Sphagnum shoots in bogs, fens and muskeg. It has a circumboreal distribution and is relatively common in suitable habitat. Its fruits are smaller than those of the commercially cultivated American cranberry, but have a similar flavor. While the small cranberry is not cultivated, its fruits have a superior antioxidant profile than American cranberry, making it a potential source of germplasm for cranberry breeding programs. This is particularly important, as wild populations of American cranberry have relatively low genetic diversity. Despite its economic potential, the classification of small cranberry is currently unresolved and remains controversial and clouded by morphological and chromosomal count studies. This study applied several innovations that distinguish it from previous work. First, we derived our data from extensive field collections along a 1000 km transect that includes the natural range of American cranberry in the south, small cranberry in the north, as well as the intermediate region where only small cranberry is expected. Previous work on this group was limited to Europe, outside the native range of American cranberry. Second, we applied highly informative PCR-based molecular markers (AFLP) to this system for the first time. Third, we developed two parallel data sets, one combining morphological and chromosomal count data, and a second combining molecular and chromosomal count data. No other study of this group has combined molecular, morphological and chromosomal count data from the same populations. This data will be useful for future studies about natural cranberry diversity and natural population characteristics as well as other cranberry breeding and genetics studies. Unique cranberry types can be generated by the hybridization of American cranberry and small cranberry populations.

Technical Abstract: Vaccinium oxycoccos s. l. is a complex of diploid and polyploid plants. The evolutionary relationship between the cytotypes is uncertain, with conflicting treatments in recent taxonomic studies. To clarify this situation, we investigated the relationships among ploidy, morphology and genetic diversity in this group. We collected samples from a 1000 km transect in eastern Canada. We used flow cytometry to determine DNA ploidy, completed a morphometric analysis of flowering stems, and assessed genetic diversity using AFLPs. Diploids only occurred growing in mixed populations with tetraploids. There were statistically significant morphological differences between ploidies; however, tetraploid variation encompasses the diploid range for most characters. AFLP data demonstrate that the tetraploids have undergone genetic divergence since their formation, obscuring whether they are auto- or allopolyploids. Our results support the conclusions of earlier work in northwestern North America and Europe, but conflict with previous morphological work in eastern North America. Our data indicate that diploids and tetraploids co-occur much more frequently than previously recognized, which may explain this discrepancy. We recommend recognizing diploids and tetraploids at the rank of variety. The distribution of the two varieties in North America suggests two hypotheses regarding the successful establishment of the tetraploid: their success is due to their capacity to exploit novel habitats outside the range of the diploid; or the tetraploid has in fact already out competed the diploid in large areas of its former range, limiting it to the far north. While we cannot rule out ongoing gene-flow between diploids and tetraploids, it is likely a rare phenomenon in this group.