Molecular Mapping of Complex Traits - Genetics, Genomics and Breeding of Crop Plants - page 141

molecular genetics is now producing significant results by using the new
technologies to influence basic and applied research in sunflower
improvement.
With the advent and development of DNA markers, it became possible
to construct saturated genetic maps and to locate quantitative trait loci (QTL)
for numerous phenotypes in plants, animals and humans. In sunflower,
several molecular genetic linkage maps have been constructed using
restriction fragment length polymorphism (RFLP), random amplified
polymorphic DNA (RAPD), amplified fragment length polymorphism
(AFLP), simple sequence repeat (SSR), insertion/deletion (INDEL), single
nucleotide polymorphism (SNP) and target region amplification
polymorphism (TRAP) markers (Berry et al. 1995; Gentzbittel et al. 1995,
1998; Jan et al. 1998; Flores-Berrios 2000a; Burke et al. 2002; Mokrani et al.
2002; Bert et al. 2003, 2004; Langar et al. 2003; Yu et al. 2003; Rachid Al-
Chaarani et al. 2004; Lai et al. 2005; Hu et al. 2007; Poormohammad Kiani et
al. 2007a; Yue et al. 2008a). The advantage of these kinds of maps is that in
cases where they have common markers with some other maps, they can be
combined in order to construct integrated maps with more markers. These
maps are widely used for understanding the genetic basis of complex traits
in sunflower.
5.2 Identification of Quantitative Trait Loci
5.2.1 Agronomic Traits
The principal goal of sunflower breeding programs is the development of
new cultivars with a high oil yield. Identification of the chromosomal
regions, which affect grain yield, oil percentage in grain and other agronomic
traits should increase our understanding of the genetic control of the
characters and help us to develop marker-assisted selection (MAS) programs.
5.2.1.1 Days from Sowing to Flowering
The genetic and environmental controls of flowering in sunflower are
certainly complex and mostly undefined. The flowering phenotype in
sunflower has been assessed as days from sowing to flowering (DSF or STF)
or days from emergence to flowering (DTF) in most of genetical studies. DSF
or DTF is an important trait because cultivars with certain ranges of growth
cycle length provide optimum yield in specific environments. Photoperiod
and temperature have major effects on STF/DTF and could be important
sources of genotype×environment interaction (Leon et al. 2001). Polygenic
inheritance patterns have been reported for DSF in most studies (Stoenescu
1974; Machacek 1979; Leon et al. 2000), although there is evidence of genetic