Submitted to: Southern Nursery Association Research Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2006
Publication Date: 12/1/2005
Citation: Fain, G.B., Atland, J.E., Rinehart, T.A. 2005. Molecular and morphological characterization of cardamine species. Southern Nursery Association Research Conference, pp 454-456. Interpretive Summary: This study was conducted to identify and compare species of bittercress (Cardamine) occurring in container crops and field soils. Previously, researchers including the authors of this paper have referred to the bittercress in container nurseries as hairy bittercress (C. hirsuta L.). It is certainly, at least from a research perspective, important to know the species of weeds infesting container nurseries and those being studied in research trials. Weed seed used in research should be the same as those infesting production nurseries. As results of this study indicate, species in containers might not be the same as native or introduced species occurring in the landscape. Another important consideration is that different species might react differently to container nursery management practices.
Technical Abstract: Cardamine sp. are problem weeds in container nurseries. It has been previously reported that Cardamine occurring in nursery containers is the introduced species C. hirsuta L.(hairy bittercress). It commonly grows as a winter annual throughout the southern, eastern and west coast areas of the US. Some have suggested that Cardamine occurring in northwest nurseries might be the native Cardamine oligosperma Nutt. (little western bittercress). Others have suggested that the introduced species C. flexuosa With. (woodland bittercress) might also occur in nurseries and greenhouses. Seed or plants were collected from container plants in Alabama (ALC), Mississippi (three locations MSC1, MSC2, and MSC3), New York (NYC), Oregon (ORC), and Virginia (VAC). Seed were also purchased as C. hirsuta from England (UKH) (Herbiseed). Another seed source was provided from Virginia (VAF) labeled as C. flexuosa. Plants were also collected from the landscape in Mississippi (MSL) and Oregon (ORL) and from container plants from Florida (FLC). Phylogenetic analysis of the ITS sequence data suggest there were three distinct species of Cardamine in our collection. Based on DNA sequence data, plants from ORL, VAC, UKH, and MSL are C. hirsuta with an average pairwise sequence similarity of 98.2%. Similarly, data for MSC1, MSC2, MSC3, ALC, NYC, and VAF match reference sequences for C. scutata Thunb. (Japanese bittercress, native to Alaska) with an average pairwise sequence similarity of 99.4%. The ORC sample produced ITS data that could not be identified based on sequences deposited in GenBank. However, confidence is high that it is not C. hirsuta or C. scutata. It is likely that ORC is a species not represented in GenBank at this time. Morphological data support the phylogenetic analysis. ORL, VAC, UKH, and MSL all exhibit pubescent leaves and 100% of the flowers for all specimens had 4 stamens. By comparison the leaves of all other taxa were glabrous and 100% of the flowers with 6 stamens. The literature supports pubescent leaves and 4 stamens per flower for C. hirsuta. While ORC was not positively identified by phylogenetic analysis, morphologically it does appear similar to descriptions of C. oligosperma, and thus could be as speculated.