Safflower is an annual, self-compatible, thistle-like, diploid (2n = 24) crop believed to have a single origin of domestication in the Fertile Crescent region dating to approximately 4000 years ago (Knowles and Ashri 1995, Chapman et al. 2010). Its haploid genome size is approximately 1.4 Gb (Garnatje et al. 2006). Safflowers have long taproots that facilitate water uptake in even the driest environments, enabling this crop to be grown on marginal lands where moisture would otherwise be limiting. Initially, safflower was cultivated for its flowers which were largely used for dyes as well as in teas and as a food additive. Safflower florets have also been used for medicinal purposes in some parts of the world. For example, extracts from these florets have been shown to reduce hypertension and reduce blood cholesterol levels (Wang Guimiao and Li Yili 1985).

More recently, safflower has been selected for its high quality, healthy seed oil which is rich in polyunsaturated fatty acids. Commercialization of safflower as an oilseed crop first began in North America during the 1950s, approximately 50 years after it was brought to North America (Knowles 1958). Safflower breeding programs that began in the 1940s and 1950s investigated the inheritance of various traits, such as flower color, spininess, and oil content. Meanwhile, Paulden F. Knowles, “the father of California safflower,” played a key role in introducing and developing safflower as a crop within the United States (McGuire et al., 2012). During the 1950s and 1960s, Knowles traveled throughout North Africa, the Middle East, and South Asia in an effort to collect germplasm representative of safflower and its wild relatives found throughout their native range. Knowles continued to study safflower throughout the remainder of his career and his work included investigations of the cytotaxonomic relationships within the genus Carthamus as well as fatty acid variability among safflower accessions (Ashri and Knowles 1960, Knowles 1972).

The germplasm that Knowles collected and developed is among the more than 2300 accessions of safflower currently maintained by the USDA. Geographical source information and morphological descriptors have been used to identify a “core” subset within the entire safflower germplasm, as listed in the Germplasm Resources Information Network. Early population genetics studies have been used to describe this core as well as other parts of the safflower germplasm, though these studies were limited to dominant markers such as randomly amplified polymorphic DNA (RAPDs) and amplified fragment length polymorphisms (AFLPs) (e.g., Sehgal and Raina 2005, Johnson et al. 2007, Amini et al. 2008). In recent years, safflower has also been proposed as a platform for the production of plant-made pharmaceuticals. For example, by transforming safflower with a chimeric fusion of the human insulin gene and the gene encoding the safflower oleosin protein, the Canadian company Sembiosys hopes to produce insulin in safflower seeds and thereby increase the world’s supply of insulin (Markley et al. 2006).

• Microsatellite primer pairs (104): available online
• Conserved orthologous primer pairs (232) and corresponding amplification size and frequency data: available online
• C. tinctorius ESTs (41,584 Sanger reads) on GenBank as of 12/2012: available here
• EST library for progenitor (Carthamus palaestinus Eig.) based on 454 sequencing (243 Mbp) – not yet available online
• EST library for invasive genotype (Carthamus oxyacanthus M. Bieb.) based on 454 sequencing (91 Mbp) – available online
• Germplasm (2383 accessions) available from USDA: available online

The CGP has been involved in the generation of genomic resources, marker development, germplasm characterization, and population development in safflower. This has included the identification of the wild progenitor of safflower (C. palaestinus Eig.; Chapman et al. 2007a), the generation of ca. 40,000 Sanger EST reads from safflower, 454 transcriptome sequencing of C. palaestinus and C. oxyacanthus M. Bieb. (a noxious weed that has been naturalized in parts of North America), the development and phenotypic characterization of a QTL mapping population derived from a cross between safflower and its wild progenitor, the development of conserved orthologous markers that cross-amplify in safflower and other related species (Chapman et al. 2007b), the development of ca. 100 EST-SSRs for use in safflower (Chapman et al. 2009), and population genetic analyses of a subset of the safflower germplasm collection (Chapman et al. 2010).

Single nucleotide polymorphisms (SNPs) identified via comparison of the C. tinctorius and C. palaestinus EST/transcriptome assemblies have been used to develop a 384-plex Illumina VeraCode GoldenGate genotyping assay. This assay will be used to genotype an aforementioned QTL mapping population and will thus provide the basis for genetic mapping and subsequent QTL identification. Although SSR- and RFLP-based maps already exist for safflower and the weedy C. oxyacanthus (Mayerhofer et al. 2010), this will be the first genetic map based on a cross between safflower and its wild progenitor, C. palaestinus. This map will thus enable an investigation of the genetic architecture of safflower domestication. Many of the SNPs genotyped in this study reside in genes having homologs that are already mapped lettuce and sunflower, thereby facilitating comparative analyses across the family. Additionally, many of the traits studied in this QTL analysis have also been studied in sunflower and lettuce (e.g., flowering time, percent seed oil, and seed oil composition), which will enable “comparative QTL mapping” throughout the Compositae and provide initial insight into whether selection has acted upon similar sets of genes throughout these species.

The CGP will be sequencing and assembling the safflower gene space (i.e., the low copy, gene-rich fraction of the genome) using Illumina sequencing technology. Additionally, targeted genotyping-by-sequencing of 96 F2 individuals from the C. palaestinus x C. tinctorius mapping population will facilitate the construction of a high density genetic map of the safflower genome, thereby enabling detailed comparison of genome evolution with other extensively studied organisms within the Compositae. Finally, C. tinctorius and C. oxyacanthus transcriptome data will be compared as part of an investigation into which genetic characteristics differentiate crops from weeds.

(bold denotes CGP authorship):

Amini F, G Saeidi, and A Arzani. 2008. Study of genetic diversity in safflower genotypes using agro-morphological traits and RAPD markers. Euphytica 163: 21-30.

Ashri A and PF Knowles. 1960. Cytogenetics of safflower (Carthamus L.) species and their hybrids. Agronomy Journal 52: 11-17.

Chapman MA and JM Burke. 2007a. DNA sequence diversity and the origin of cultivated safflower (Carthamus tinctorius L.; Asteraceae). BMC Plant Biology 7 : 60.

Chapman MA, JC Chang, D Weisman, RV Kesseli, and JM Burke. 2007b. Universal markers for comparative mapping and phylogenetic analysis in the Asteraceae (Compositae). Theoretical and Applied Genetics 115: 747-755.

Chapman MA, J Hvala, J Strever, M Matvienko, A Kozik, RW Michelmore, S Tang, SJ Knapp, and JM Burke. 2009. Development, polymorphism, and cross-taxon utility of EST-SSR markers from safflower (Carthamus tinctorius L.). Theoretical and Applied Genetics 120: 85-91.

Chapman MA, J Hvala, J Strever, and JM Burke. 2010. Population genetic analysis of safflower (Carthamus tinctorius; Asteraceae) reveals a Near Eastern origin and five centers of diversity. American Journal of Botany 97(5): 831-840.

Garnatje T, S Garcia. R Vilatersana, and J Valles. 2006. Genome size variation in the genus Carthamus (Asteraceae, Cardueae): Systematic implications and additive changes during allopolyploidization. Annals of Botany 97: 461-467.

Johnson RC, TJ Kisha, and MA Evans. 2007. Characterizing safflower germplasm with AFLP markers. Crop Science 47:1728 – 1736.

Knowles PF. 1958. Safflower. Advances in Agronomy 10: 289-323.

Knowles PF. 1972. The plant geneticist’ contribution toward changing lipid and amino acid composition of safflower. Journal of the American Oil Chemists’ Society 49(1):27-29.

Knowles PF and A Ashri. 1995. Safflower: Carthamus tinctorius (Compositae). in Evolution of Crop Plants 2nd edition. Edited by: Smartt, J. and Simmonds, N.W. Harlow, UK , Longman, 47 - 50.

Markley N, C Nykiforuk, J Boothe, and M Moloney. 2006. Producing proteins using transgenic oilbody-oleosin technology. Biopharm International 19(6): 34-57.

Mayerhofer R, C Archibald, V Bowles, and AG Good, A.G. 2010. Development of molecular markers and linkage maps for the Carthamus species C. tinctorius and C. oxyacanthus Genome 53: 266-276.

McGuire, P.E., A.B. Damania, and C.O. Qualset (eds.) 2012. Safflower in California. The Paulden F. Knowles personal history of plant exploration and research on evolution, genetics, and breeding. Agronomy Progress Report No. 313, Dept. of Plant Sciences. University of California. Davis CA USA.

Sehgal D and SN Raina. 2005. Genotyping safflower (Carthamus tinctorius) cultivars by DNA fingerprints. Euphytica 146: 67-76.

Wang Guimiao and Li Yili. 1985. Clinical application of safflower (Carthamus tinctorius). Zhejiang Traditional Chinese Medical Science Journal 1:42-43.