Improving the yellow pigment content of bread wheat flour by selecting the three homoeologous copies of Psy1

Abstract

The yellow pigment content (YPC) of endosperm affects the quality and nutritional value of wheat grain products. Major quantitative trait loci (QTL) for endosperm YPC have been repeatedly mapped on chromosomes 7A and 7B in durum and bread wheats. The genes coding for phytoene synthase (PSY1), which is involved in the biosynthesis of carotenoids, generally co-segregate with these QTL, indicating their role in determining YPC. Here, to study the genetic factors underlying endosperm YPC in bread wheat, the sequence polymorphism of the homoeologous A, B and D copies of genes coding for PSY1, Psy-A1, Psy-B1, and Psy-D1, was studied in a worldwide core collection, which was also phenotyped for flour YPC. Seven novel alleles of Psy-A1 and two novel alleles of Psy-B1 were detected, which confirms the high level of polymorphism of these genes. Two major QTL with respective candidate genes Psy-A1 and Psy-B1 were identified in the distal region of chromosomes 7A and 7B using progeny of a cross between Apache and Ornicar, high and low YPC cultivars, respectively. Association mapping confirms the role of these genes in YPC and shows that the D copy also significantly influences this trait. These results indicate that breeders need to consider all three Psy1 copies when seeking to improve the YPC of wheat endosperm

The colours of durum wheat: a review

“…The PSY are also considered as the ratelimiting enzymes for this pathway, and the PSY1 enzymes, in particular, are required for carotenoid accumulation by the endosperm (Gallagher et al 2004;Li et al 2008). Almost 50 different alleles have been identified at the Psy-A1 and Psy-B1 loci in different species of wheat (He et al 2008(He et al , 2009aHowitt et al 2009;Singh et al 2009;Wang et al 2009;Crawford et al 2011;Ravel et al 2013) (Table 1). The genes coding for PSY were mapped to the chromosome 7 groups by Pozniak et al (2007); in particular, the Psy-B1 locus co-segregated with a QTL on chromosome 7B, which demonstrated an association between the position of this gene and part of the phenotypic variation for endosperm colour (Pozniak et al 2007;Roncallo et al 2012).…”

“…Positive associations were found between YPC and the Psy1-A1o allele in a collection of 93 cultivars of durum wheat and in a recombinant inbred line population (Singh et al 2009), with the Psy-A1t allele in a panel of 30 Australian lines of bread wheat and Psy-A1p allele in the segregating population Ajana  WAWHT2074, in which the locus controls 32-36% of the observed variability for the trait (Howitt et al 2009;Crawford et al 2011). Seven new alleles for Psy-A1 and two new alleles for Psy-B1 were recently identified in bread wheat by Ravel et al (2013). Moreover, the marker Psy-A1_R_49 was shown to be associated with high YPC in a core collection of 372 genotypes.…”

Improving durum wheat (Triticum turgidum L. var durum) grain yellow pigment content through plant breeding

“…In parallel, the corresponding PSY1A values of the explained variation of this trait have been medium (10-30%), high (30-50%) and very high (> 50%) (Blanco et al, 2011) in durum wheat. In the case of PSY1B, the percentages of explained variability of endosperm yellowness reported have been very high (> 50%) in common wheat (Ravel et al, 2013), and low (< 10%) to medium (10-30%) Roncallo et al, 2012) in durum wheat. The effect of the PSY1D locus on the yellowness of the endosperm has been less well studied, but recent evidence shows that it also significantly influences this trait (Ravel et al, 2013).…”

“…In the case of PSY1B, the percentages of explained variability of endosperm yellowness reported have been very high (> 50%) in common wheat (Ravel et al, 2013), and low (< 10%) to medium (10-30%) Roncallo et al, 2012) in durum wheat. The effect of the PSY1D locus on the yellowness of the endosperm has been less well studied, but recent evidence shows that it also significantly influences this trait (Ravel et al, 2013). However, the percentages of endosperm yellowness or GYPC variability explained by the PSY1 loci are not reported in several studies (Pozniak et al, 2007, Reimer et al, 2008Dubcovsky, 2008, He et al, 2009a;He et al 2009b;Singh et al, 2009).…”

“…In addition, major QTLs on chromosomes 7A and 7B were detected in common wheat (Parker et al, 1998;Ma et al, 1999;Mares and Campbell, 2001;Kuchel et al, 2006;He et al, 2008;Zhang et al, 2009), demonstrating the importance of these two chromosomes for the endosperm yellowness. (Ravel et al, 2013), medium (10-30%) (He et al, 2008;Zhang et al, 2009;Ravel et al, 2013), high (30-50%) (Zhang et al, 2009), and very high (> 50%) (Howitt et al, 2009) in common wheat. In parallel, the corresponding PSY1A values of the explained variation of this trait have been medium (10-30%), high (30-50%) and very high (> 50%) (Blanco et al, 2011) in durum wheat.…”