Measurements of gene flow using molecular markers

There are three approaches to solve this problem:

1. The analysis of mixed natural populations of T. koksaghyz and related, sympatric or parapatric polyploid forms to detect possible gene flow;

Two natural populations of koksaghyz and sympatric or parapatric apomicts were screened by means of eleven gene KASP markers. No indication of introgression was detected.

2. The analysis of Taraxacum flora at, or in the vicinity of, sites of koksaghyz cultivation in the past to look for possible features of gene introgression;

21 populations were screened for hybrid genotypes at or near the historical sites of koksaghyz mass cultivation using KASP markers. At none of the 21 populations dandelion plants were observed with obvious TKS morphological traits. For DNA analysis, at 18 locations 24 plants per site were sampled (leaf disks). At three locations close to a former seed production sited 48 plants were sampled per site. In total DNA was extracted from 576 plants. After a repeated analysis of seven unclear cases, no unequivocal sign of introgression was detected.

A map of Skåne, southern Sweden, with the locations of the sampled dandelion populations. The dashed circles indicate a radius of 1 and 2 kilometer around the two historical seed production sites, Tomelilla and Hammenhog.

3. The analysis of koksaghyz crossability with a wide range of polyploid congeners.

Under experimental conditions, a variety of parental combinations were tested to characterize the crossability of T. koksaghyz with other, either related or unrelated dandelions. Most of the crosses did not yield any seed; in the case of related apomicts (probably involving one or more koksaghyz genomes through allopolyploidy) the seed set is estimated as an average of one achene per 50 × 50 floret crosses. The existence of established allopolyploid apomicts close to the sexual T. koksaghyz show that occasionally a viable natural hybridogenous line may persist and establish as an apomictic species. Experimental hybrids obtained show a limited potential of gene flow with the T. koksaghyz parentage.