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Scheme of crossing strategies. Tragopogon dubius and T. porrifolius (or T. pratensis) were used as either the maternal or paternal parent; each cross (line) gave rise to sterile diploid F1 progeny. To double chromosomes and restore fertility of these hybrids, seeds were treated with colchicine, obtaining fertile allotetraploid S0 plants. These individuals were selfed to produce lineages of fertile allotetraploid hybrids (generation S1, S2).
