Carotenoid Pigment Content in Durum Wheat (Triticum turgidum L. var durum): An Overview of Quantitative Trait Loci and Candidate Genes

Abstract

Carotenoid pigment content is an important quality trait as it confers a natural bright yellow color to pasta preferred by consumers (whiteness vs. yellowness) and nutrients, such as provitamin A and antioxidants, essential for human diet. The main goal of the present review is to summarize the knowledge about the genetic regulation of the accumulation of pigment content in durum wheat grain and describe the genetic improvements obtained by using breeding approaches in the last two decades. Although carotenoid pigment content is a quantitative character regulated by various genes with additive effects, its high heritability has facilitated the durum breeding progress for this quality trait. Mapping research for yellow index and yellow pigment content has identified quantitative trait loci (QTL) on all wheat chromosomes. The major QTL, accounting for up to 60%, were mapped on 7L homoeologous chromosome arms, and they are explained by allelic variations of the phytoene synthase (PSY) genes. Minor QTL were detected on all chromosomes and associated to significant molecular markers, indicating the complexity of the trait. Despite there being currently a better knowledge of the mechanisms controlling carotenoid content and composition, there are gaps that require further investigation and bridging to better understand the genetic architecture of this important trait. The development and the utilization of molecular markers in marker-assisted selection (MAS) programs for improving grain quality have been reviewed and discussed.

Keywords: carotenoids; durum wheat; grain yellow pigment content; marker-assisted selection; yellow index.

Figure 1

Schematic carotenoid pathway. The main components of the biosynthetic chain have been reported in the figure in black font, while all the enzymes involved are blue. The proteins from the related pathways are indicated in red.

Figure 2

Schematic representation of durum wheat chromosomes [based on theMaccaferri et al. (2014) map] and quantitative trait loci (QTL) summary for yellow pigment content (YPC) or yellow index (YI) trait detected in references in Table 1 . Markers, on the right chromosome side, are reported every 20 cM approximately. cM distances are indicated on the left side of the bar. Red solid bars indicate the QTL confidence interval regions. The red bars report the reference publication numbers in red (as in Table 1 and Table S1 ) and the QTL R2 range value in black. 1, Elouafi et al. (2001); 2, Pozniak et al. (2007); 3, Zhang et al. (2008); 3b, Zhang and Dubcovsky (2008); 4, Reimer et al. (2008); 5, Patil et al. (2008); 6, Singh et al. (2009); 7, He et al. (2009); 8, Blanco et al. (2011); 9, Roncallo et al. (2012); 10, Colasuonno et al. (2014); 11, Campos et al. (2016); 12, N’Diaye et al. (2017); 13, Colasuonno et al. (2017a); 14, Rosello et al. (2018); 15, N’Diaye et al. (2018); 16, this study.