Development of EST-SSR markers and their utility in revealing cryptic diversity in safflower (Carthamus tinctorius L.)

With the aim of developing additional genomic resources in safflower, a set of 41,011 ESTs of safflower were mined for the presence of SSRs. 18,773 SSR containing ESTs (SSR-ESTs) were identified and were analyzed to remove redundant sequences leading to identification of 8,810 non-redundant SSR-ESTs (categorized into 6104 singletons and 2,706 contigs) having 13,085 non-redundant SSRs. The average number of non-redundant SSRs per EST was 0.32 and they predominantly consisted of dinucleotide (57.7 %), and trinucleotide (37.7 %) repeat motifs. 500 primer pairs were designed for the non-redundant EST-SSRs of which, 151 were tested. 60 markers which gave robust amplicons, were validated in a set of 19 Carthamus lines. A subset of EST-SSR markers, having average polymorphism information content (PIC) ≥0.4 could precisely elucidate the pedigree relatedness among these lines. Further, these markers exhibited high cross-species transferability to five other wild species of Carthamus. The markers reported here would be a valuable addition to existing safflower marker resources aiding in hastening its improvement.