Chloroplast DNA diversity reveals the contribution of the two wild species in the origin and evolution of diploid safflower (Carthamus tinctorius L.)

The identity of the wild progenitor of one of the most important oil crop species, Carthamus tinctorius (2n = 2x = 24), commonly known as safflower, has been the subject of numerous studies at morphological, biochemical, cytogenetic, and biosystematic levels, but no definitive conclusions have been made. The nuclear, mitochondrial, and chloroplast genomes of the two botanical varieties of C. tinctorius, C. tinctorius var. tinctorius and C. tinctorius var. inermis, and two wild species, C. palaestinus and C. oxyacantha, were assayed at the nucleotide sequence level and by DNA markers. The nuclear and mitochondrial DNA assays were not helpful in conclusively identifying the diploid ancestor of C. tinctorius. The chloroplast DNA diversity, on the other hand, unambiguously provided new and novel evidence that C. palaestinus and C. oxyacantha contributed their plastomes to the evolution of C. tinctorius var. inermis and C. tinctorius var. tinctorius, respectively. This study, therefore, affirms a startling revelation of a rare event of two wild species contributing to the origin and evolution of safflower, a major world oilseed crop about whose genetics very little is known.