Dioscorea strydomiana (Strydom's yam)

Dioscorea strydomiana is restricted to Mpumalanga in South Africa, where it has been recorded at 1,100 - 1,150 m above sea level. It has been found growing in open acacia woodland with aloes and a grass-rich understory on steep, rocky slopes.

Adult plant showing the tuber and shoot habit. The tuber has been damaged during harvesting by collectors of medicinal plants (Image: John Burrows)

So far, only two populations of Dioscorea strydomiana have been found. A team visits those populations on a regular basis to assess their status. It is estimated that each population comprises about 100 plants. On the last visit, the team noted that one population had suffered significant damage from medicinal plant collectors, who remove parts of the tuber. Dioscorea strydomiana is thought to be slow-growing and therefore slow to recover from such damage. Burning, mining, cattle farming, firewood collection, porcupine activity and removal of plants for the horticultural trade are thought to be further threats to the species. Like almost all Dioscorea species it is dioecious (separate male and female plants) so only the female element of the populations produce seed. It has been rated as Critically Endangered (CR) according to IUCN Red List criteria.

A number of measures have already been taken to protect this species. Careful monitoring by members of the Mpumalanga Tourism and Parks Authority (MTPA), the South African National Biodiversity Institute (SANBI) and the Mpumalanga Plant Specialist Group, has found that its numbers are declining at an alarming rate, so that urgent measures to promote its sustainable use and conservation have been called for. The area in which the species grows is not yet protected, but is monitored by the local tribal authority in collaboration with the MTPA in an attempt to prevent unscrupulous and illegal collection of plant material. An attempt to set up a community-run nursery in the area to provide cultivated plants for the medicinal and horticultural trade has so far not proved successful, but collections of seed-grown individuals have been successfully established in two of SANBI’s National Botanical Gardens (NBGs). Two seed collections have been banked at Kew's Millennium Seed Bank.

Dioscorea strydomiana is used locally with another species of Dioscorea to treat cancer. Its efficacy is unknown. The related species D. elephantipes and D. sylvatica are known to contain high levels of steroidal compounds which can be used to reduce inflammation, for example in the treatment of arthritis or for the promotion of healing.

Kew's Millennium Seed Bank partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.

Number of seed collections stored in the Millennium Seed Bank: Two.
Germination testing: About 55%.

Pressed and dried specimens of Dioscorea strydomiana are held in the Herbarium, one of the behind-the-scenes areas of Kew. The details of some of these specimens can be seen on-line in the Herbarium Catalogue.

Search Kew's databases for more information on this species

Kew News story – Unique yam under threat

Mpumalanga Parks Board

South African National Biodiversity Institute (SANBI)

The Observer: New to Nature No 32: Dioscorea strydomiana

The Guardian (11 Sept 2012): World's 100 most endangered species

Priceless or Worthless (IUCN list of 100 most endangered species)