Taraxacum koksaghyz and the interspecific gene flow

Crossing experiments between Taraxacum koksaghyz (TKS) and related dandelion species indicate that hybridization is possible. This may result in interspecific gene flow in regions where TKS is cultivated and in SE Kazakhstan where TKS is growing in the wild. Both situations were investigated in this report. To determine whether 66 years after the end of seed production of TKS in the Swedish county of Skåne still traces of TKS were present in the environment, a detailed large scale population genetic study was carried out. At different distances to two fields where between 1947 and 1950 tens of millions of TKS seeds were produced, in total 576 wild common dandelions (Taraxacum officinale, TO) in 21 populations were sampled. These plants were genotyped for 10 codominant TKS- or TO-specific KASP DNA markers. In total 14652 alleles were typed. Not a single TKS-specific allele was found. This is consistent with the absence of TKS-specific morphological characteristics at the sampled locations. Although this negative result in the sample set cannot exclude the possibility of hybridization and introgression absolutely, it is clear that the impact of TKS seed production after almost 70 years in Skåne has to be very low. This result may be extrapolated to the future cultivation of TKS in regions where no sexual diploid Taraxacum species occur, which is in western Europe north of 52 degrees latitude. In its native range in SE Kazakhstan TKS is spatially isolated from related dandelion species by habitat differentiation. However, at disturbed sites TKS may grow intermingled with other dandelion species. Two of such disturbed locations were investigated. From the combined analysis of ploidy level, reproduction mode and multilocus KASP genotypes, we infer that there is no indication for gene flow between TKS and sympatric Taraxacum species in natural populations in SE. Kazakhstan. TKS populations in SE. Kazakhstan are therefore not likely to be threatened by gene swamping caused by other dandelion species.

TKS locality near Kegen, SE. Kazakhstan