Available exsitu germplasm of the potential rubber crop Taraxacum koksaghyz belongs to a poor rubber producer, T. brevicorniculatum (Compositae–Crepidinae)
Cultivation of the Russian dandelion (Taraxacum koksaghyz) as a rubber producing crop was abandoned more than 50 years ago. Recently the interest in the Russian dandelion has renewed, due to the increasing demand for natural rubber, health problems associated with Hevea rubber and the potential vulnerability of the Hevea production system. Morphological examination and genetic analyses demonstrated that all available ex situ germplasm collections of T. koksaghyz belonged to a single triploid apomictic clone that was misidentified as T. koksaghyz. Morphological, taxonomic and AFLP analyses show that this clone belongs to T. brevicorniculatum a species commonly co-occurring with wild populations of T. koksaghyz in the southeastern Kazakhstan. The type specimen of T. brevicorniculatum is no longer extant and we provide a detailed description and typification, and the characteristics that distinguish it from T. koksaghyz. The investigation of literature reports and herbarium collections indicates that T. koksaghyz seed batches in the past were often contaminated with T. brevicorniculatum. We discuss the possible reasons for the worldwide replacement of T. koksaghyz by a single T. brevicorniculatum clone. New introductions in ex situ collections are urgently needed.