Taraxacum koksaghyz


Taraxacum koksaghyz (TKS) is a wild, non-domesticated plant species, and therefore has as relatively low root (the main source of natural rubber) and rubber yield. TKS was cultivated on a large scale in the Soviet Union between 1931 and 1950, as well as in the United States, the UK, Germany, Sweden and Spain during World War II as an emergency source of rubber when supplies of rubber from Hevea brasiliensis in South East Asia were threatened. During this time period, the highest yields achieved in the U.S. were 110 kg of rubber per hectare, while the USSR achieved yields of 200 kg of rubber per hectare. With the conclusion of World War II and the return of affordable Hevea brasiliensis rubber, the majority of TKS programs were discontinued.

TKS was discovered in 1931 in the framework of a program to make the USSR self-sufficient in strategic materials, including NR. Subsequently, efforts were made to domesticate and improve the crop. TKS was cultivated on a large scale in the Soviet Union between 1931 and 1950, as well as in the United States, the UK, Germany, Sweden and Spain during World War II as an emergency source of rubber when supplies of rubber from Hevea brasiliensis in Southeast Asia were threatened. In the USSR, a combined total of 67,000 hectares was planted in 1941, and agronomic procedures and processing methods were tested. The highest yields achieved in the United States were 110 kg of rubber per hectare, while the USSR achieved yields of 200 kg of rubber per hectare. The USDA and the US Forest Service were able to produce NR that was successfully applied in tyres (Whaley and Bowen, 1947). With the conclusion of World War II and the return of affordable Hevea brasiliensis rubber, the majority of TKS programs were discontinued. All Russian TKS germplasm got finally lost. In EU-PEARLS, a new collection of TKS was built, though it covers only a part of all possible genetic diversity. Only scattered reports on TKS have appeared since. However, these indicate that breeding can rapidly increase the rubber content. In addition, the molecular weight of rubber extracted from TKS is higher than of Hevea and guayule rubber (thus explaining the good quality of the tires made during WWII).

Current developments

Since the 1990’s new research programs were started in the US targeting at alternative rubber crops. Initially these programs focused on Guayule, but since the last five years several new initiatives started that specifically focused on TKS. Within the PENRA initiative (The "Program of Excellence in Natural Rubber Alternatives) seven parties (four Universities and three tyre companies) jointly develop TKS as a novel rubber crop. Leading party in this initiative is the University of Ohio.

Roots of wild TKS plants contain on average 5% of NR. In the EU-PEARLS project, it was demonstrated that TKS plants can be crossed with other, larger and apomictic dandelion species, such as T. brevicorniculatum. This is important, because it means that progress is not limited to the TKS gene pool. Apomictic hybrids were larger than both parents and produced apomictic seeds in the absence of cross-pollination. Only a few of these hybrids produced in EU-PEARLS were analyzed for rubber content, which turned out to be intermediate between the two parental species. However, many of these interspecific apomictic hybrids and advanced backcrosses have not yet been investigated for rubber content.

Photos: Jan Kirschner