Mapping and Tagging of Simply Inherited Traits - Genetics, Genomics and Breeding of Crop Plants - page 132

of 37% but strongly influenced by the temperature during seed maturation
(Fernández-Moya et al. 2002). Genetic studies demonstrated the presence of
partially recessive alleles at two independent loci Es1 and Es2 in CAS-3
(Pérez-Vich et al. 1999). The high stearic acid trait of CAS-14 was shown to
be controlled by a single recessive gene, designated es3 (Pérez-Vich et al.
2006a). Candidate-gene and QTL analyses demonstrated that Es1 co-
segregated with a stearoyl-acyl carrier protein (ACP) desaturase locus
(SAD17A) located on LG 1 of the sunflower genetic map (Perez-Vich et al.
2002). The es3 gene was mapped on LG 8, closely linked to Ms11 , a gene
determining nuclear male sterility (Perez-Vich et al. 2006b). Fernández-Moya
et al. (2003) reported that es3 might be associated to a regulatory
thermosensitive element that determines a lower expression of the stearate
desaturase at high temperatures. Further candidate genes putatively
involved in stearic acid biosynthesis were mapped by Pérez-Vich et al.
(2004b). Two secondary SAD6 loci were mapped to LG 1 and LG 4, the
primary locus has been found to map on LG 11. One FatB fragment was
mapped to LG 7 and FatA gene probes (FatA-A, FatA-B) were mapped to LG
1, linked to SAD17, and LG 2, respectively. In addition an oleate desaturase-
like gene was mapped on LG 1.
4.6.2 Tocopherol Composition
As an important nutrient for human beings, vitamin E has been well known
for its antioxidative properties (Kamal-Eldin and Appleqvist 1996). It
consists of tocopherols and tocotrienols. Alpha-tocopherol exerts the most
active biological activity (Traber and Sies 1996) but shows the weakest
antioxidant potency in vitro. Beta-, gamma-, and delta-tocopherol possess a
lower vitamin E value, but have considerably greater in vitro antioxidant
potency than alpha-tocopherol (Pongracz et al. 1995). Sunflower normally
produces >90% alpha-tocopherol (Sheppard et al. 1993). However, three
loci ( m = Tph1 , g = Tph2 , and d ) are known to disrupt the synthesis of alpha-
tocopherol and produce a broad spectrum of off-type tocopherol profiles in
sunflower seeds (Demurin 1993; Demurin et al. 1996; Hass et al. 2006; Tang
et al. 2006b). The Tph1 gene, conferring increased beta-tocopherol content to
sunflower seeds, has been mapped to the upper end of LG 1 (Tang et al.
2006b) and co-segregated with the SSR markers ORS1093, ORS222 and
ORS598 (Vera-Ruiz et al. 2006). Tph2 was mapped to LG 8 (Hass et al. 2003),
about 30 cM down-stream from the upper end of this LG (García Moreno
et al. 2006; Hass et al. 2006). This recessive gene affects a high gamma-
tocopherol content. The d mutation partially disrupts the synthesis of alpha-
tocopherol and causes an accumulation of beta-tocopherol. The d gene was
tightly linked to ORS676 and mapped to LG 4 (Tang et al. 2006b). Further
analyses of the genes of the tocopherol biosynthetic pathway and the