Crambe maritima (sea kale) is a halophytic perennial plant in the genus Crambe and a member of the Brassicaceae. Over 10,000 species of halophyte are known, but only 250 have the potential as staple crops, making C. maritime (which has large edible leaves once popular as a blanched spring vegetable) of possible agronomic interest as a future crop in its own right. C. maritima is endemic to Europe, with populations found at isolated sites around the coasts of the British Isles, the shores of the Baltic, the Black Sea and the Atlantic. It is also a close relative of the other members of the genus Crambe, which is the second most species-rich section of the tribe Brassiceae, after Brassica (Gomez-Campo, 1980; Warwick and Black, 1997).
Crop wild relatives can be defined as wild plant species that are genetically related a domesticated plant. In other words crop wild relatives are all those species found growing in the wild that to some degree are genetically related to food. fodder and forage crops, medicinal plants, condiments, ornamental and forestry species used by humankind. Many crop wild relatives are found growing as weeds in disturbed habitats, such as roadsides, field margins, orchards and traditionally managed agricultura. Crambe maritima is of interest as a crop wild relative of other Brassicaceous crops such as cabbage, mustard and canola . With problems brought about by climate change crop wild relatives are likely to prove important in ensuring food security for the new millennium.
Studies of Crambe maritima populations in the UK have revealed high levels of diversity between populations but lower levels of genetic diversity within them due to widespread outcrossing (Bond et al, 2005). This suggests that the Irish populations of C. maritima are likely to contain genetic characteristics of interest that are not represented in other European populations. Wild Irish populations of C. maritima are therefore a particular priority for analysis of genetic diversity. However, there has been no systematic collection or genetic assessment of the Irish populations of the crop wild relative, Crambe maritima. To date, there is only one accession of Crambe maritima of Irish origin that has been collected and stored under ex situ conditions and 15 different sites for collection of Crambe maritima have been identified in the DAFF funded priority list for conservation of crop wild relatives (Dr. Tom Curtis, Genetic Heritage Ireland, pers comm.).
Crambe maritima is not only of interest as a wild relative of other Brassicaceous crops, but also has strong potential as a new halophytic vegetable crop. The plant is sometimes grown as an ornamental but its most common use is as a blanched vegetable. The production of sea kale, and the taste, quality and marketing price of its shoots are predicted to be comparable to that of Asparagus. It is easy to propagate in rich, deep and sandy soils, and can be grown from root cuttings available from specialist nurseries. Blanching may be achieved by covering it with opaque material or using a deep, loose and dry mulch. In France, a breeding program has been running since 1992 for sea kale, as a component of efforts to bring sea kale closer to commercial production and thereby enhance the diversification of vegetable crops. A systematic collection of wild populations of C. maritima has been undertaken in France, from Quiberon (south Brittany) to Dunkerque (north France near Belgium) to broaden the genetic base of the breeding program (Briard et al, 2002). Similar studies of sea kale have been performed in the isolated populations on either side of the English Channel (Bond et al 2005). In both studies, molecular markers were used to evaluate the population diversity among the collected wild plants. However, the Irish population remains completely uncharacterised and have only had minimal conservation focus (i.e. one Irish accession collected). A key starting point for the conservation of Irish Crambe maritima genetic resources will be to collect and stiore seed (reproductive material) from Irish populations while assessing their genetic relatedness to other populations outside of Ireland.