A case study on the genetic origin of the high oleic acid trait through FAD2-1 DNA sequence variation in safflower (Carthamus tinctorius L.).

Sara Rapson,Surinder Singh,Qing Liu,Pushkar Shrestha,Craig Wood,Xue-Rong Zhou,Shoko Okada,Allan Green,Alpana Das,Man Wu

doi:10.3389/fpls.2015.00691

Abstract

The safflower (Carthamus tinctorius L.) is considered a strongly domesticated species with a long history of cultivation. The hybridization of safflower with its wild relatives has played an important role in the evolution of cultivars and is of particular interest with regards to their production of high quality edible oils. Original safflower varieties were all rich in linoleic acid, while varieties rich in oleic acid have risen to prominence in recent decades. The high oleic acid trait is controlled by a partially recessive allele ol at a single locus OL. The ol allele was found to be a defective microsomal oleate desaturase FAD2-1. Here we present DNA sequence data and Southern blot analysis suggesting that there has been an ancient hybridization and introgression of the FAD2-1 gene into C. tinctorius from its wild relative C. palaestinus. It is from this gene that FAD2-1Δ was derived more recently. Identification and characterization of the genetic origin and diversity of FAD2-1 could aid safflower breeders in reducing population size and generations required for the development of new high oleic acid varieties by using perfect molecular marker-assisted selection.

Highlights

Hybridization between domestic crop plants and their wild relatives, and the potential for gene introgression, has received widespread interest in recent years (Ellstrand et al, 1999; Jarvis and Hodgkin, 1999; Felber et al, 2007; Arrigo et al, 2011)
DNA Sequence Analyses of FAD2-1 and FAD2-2 The entire 5′ untranslated region (5′ UTR) intron of FAD2-1 was amplified (1199 bp) from all the 22 Carthamus accessions, including 17 C. tinctorius, 1 C. palaestinus, and 4 C. oxycanthus accessions, using the primers based on the its conserved flanking regions in the 5′ UTR (Table 1)
Haplotype 1 was present in C. palaestinus and C. tinctorius; haplotype 2 was unique to the C. tinctorius PI 599253, the high oleic acid cultivar Saffola 317 (S-317); haplotype 3 was exclusive to C. oxyacantha; and haplotype 4 was identified in C. tinctorius, including the PI 538779, the high linoleic cultivar Centennial

Summary

Introduction

Hybridization between domestic crop plants and their wild relatives, and the potential for gene introgression, has received widespread interest in recent years (Ellstrand et al, 1999; Jarvis and Hodgkin, 1999; Felber et al, 2007; Arrigo et al, 2011). Genetic introgression has been defined as “the permanent incorporation of genes from one set of differentiated populations into another” (Stewart et al, 2003), and the gene introgression from wild relatives has long been considered important for the evolution of domestic crop species (Stebbins, 1959; Harlan, 1965; Slatkin, 1987; Prescott-Allen and Prescott-Allen, 1988; van Raamsdonk and van der Maesen, 1996) In these cases, the maintenance of new genetic combinations, which result in populations with new characteristics, depends on both natural and human selection (Jarvis and Hodgkin, 1999). This is of particular interest in safflower (Carthamus tinctorius L.) with regards to high quality oil production

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