Abstract
BackgroundSafflower (Carthamus tinctorius L.) is an oilseed crop in the Compositae (a.k.a. Asteraceae) that is valued for its oils rich in unsaturated fatty acids. Here, we present an analysis of the genetic architecture of safflower domestication and compare our findings to those from sunflower (Helianthus annuus L.), an independently domesticated oilseed crop within the same family.We mapped quantitative trait loci (QTL) underlying 24 domestication-related traits in progeny from a cross between safflower and its wild progenitor, Carthamus palaestinus Eig. Also, we compared QTL positions in safflower against those that have been previously identified in cultivated x wild sunflower crosses to identify instances of colocalization.ResultsWe mapped 61 QTL, the vast majority of which (59) exhibited minor or moderate phenotypic effects. The two large-effect QTL corresponded to one each for flower color and leaf spininess. A total of 14 safflower QTL colocalized with previously reported sunflower QTL for the same traits. Of these, QTL for three traits (days to flower, achene length, and number of selfed seed) had cultivar alleles that conferred effects in the same direction in both species.ConclusionsAs has been observed in sunflower, and unlike many other crops, our results suggest that the genetics of safflower domestication is quite complex. Moreover, our comparative mapping results indicate that safflower and sunflower exhibit numerous instances of QTL colocalization, suggesting that parallel trait transitions during domestication may have been driven, at least in part, by parallel genotypic evolution at some of the same underlying genes.
Highlights
Safflower (Carthamus tinctorius L.) is an oilseed crop in the Compositae
We investigate the genetic basis of the domestication syndrome in the oilseed crop safflower (Carthamus tinctorius L.; Carduoideae)
Our results indicate that the genetic architecture of safflower domestication is complex, with the majority of traits being controlled by multiple quantitative trait loci (QTL) with small to moderate phenotypic effects
Summary
Safflower (Carthamus tinctorius L.) is an oilseed crop in the Compositae (a.k.a. Asteraceae) that is valued for its oils rich in unsaturated fatty acids. Because many crop species share a common suite of traits (e.g., loss of seed dormancy, uniform flowering time, and fruit size) that evolved in response to selection during domestication (referred to as the “domestication syndrome”; [3]), comparative analyses across independent crop lineages . Comparisons among QTL analyses can provide insight into the extent to which parallel phenotypic changes across independent crop lineages are driven by selection on homologous genes, or at least genomic regions. Comparative QTL mapping across crops in the Fabaceae [9], Poaceae [10,11], and Solanaceae [12] has provided evidence that many domestication traits, including increased seed weight, increased fruit size, and changes in flowering time and life history may be conditioned by independent changes in homologous genes in different lineages. Knowledge that the Arabidopsis dwarfing gene, GAI, is structurally and functionally homologous to the wheat and maize dwarfing genes RHT-B1, RHT-D1, and D8, led to the transformation of the GAI gene into basmati rice to produce dwarf varieties [13]
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