Introgression potential between safflower (Carthamus tinctorius) and wild relatives of the genus Carthamus

Safflower hybridized and produced viable offspring with members of the section Carthamus and species with chromosome numbers of n = 10 and n = 22, but not with n = 32. The T-DNA construct of a transgenic C. tinctorius line was passed on to the F1 progeny in a Mendelian fashion, except in one specific cross, where it was deleted at a frequency of approximately 21%. Analyzing fitness and key morphological traits like colored seeds, shattering seed heads and the presence of a pappus, we found no evidence of hybrid vigour or increased weediness in the F1 hybrids of commercial safflower and its wild relatives.Our results suggest that hybridization between commercial safflower and its wild relatives, while feasible in most cases we studied, does not generate progeny with higher propensity for weediness.The genus Carthamus is a diverse group of plants within the Asteraceae and is of interest due to the commercial growth of one member, C. tinctorius (safflower) as well as for its potential as a model system to examine the introgression of agronomic and weedy traits across species boundaries and to study the invasiveness of wild relatives of a crop. Safflower is grown in several countries as an oilseed crop and for birdseed and is being evaluated as a crop platform for molecular farming [1]. The different species of Carthamus have been classified into several different grouping systems by different taxonomists. Estilai and Knowles [2] originally placed 13 species in the genus Carthamus into five sections, based on chromosome numbers. Lopez-Gonzalez [3] rearranged the 15 species that he identified into three sections (Carthamus, Odonthagnathis and Atractylis), to match the understanding of the relationships between the species and their chromosome numbers. In the scheme proposed by Vilatersana et al. [4], the section Carthamus contains the species with 12 sets of chromosomes including C. tinctorius, C. palaestinus and C. oxyacanthus. The section Atractylis (n = 10, 11, 22, 32