Molecular Mapping of Complex Traits - Genetics, Genomics and Breeding of Crop Plants - page 164

was used and “ ms 6 ” and “ ms 7 ” were mapped on linkage groups 16 and 6,
respectively. The gene “ ms 6 ” was flanked by ORS807 and ORS996 at
distances of 7.9 cM and 18.5 cM, respectively, and “ ms 7 ” was flanked by
ORS608 and Tg3r165a-185 at distances of 2.6 cM and 4.7 cM, respectively.
These molecular markers can offer a quick and precise detection of genotypes
bearing a male sterility allele useful in hybrid production.
5.2.5 Physiological Traits
Yield components and oil production are known to be positively correlated
with photosynthesis and water status traits in sunflower. Hervé et al. (2001)
identified QTLs for photosynthesis and water status traits using RILs from
the cross PAC2×RHA 266; and the results are summarized in Table 5-1.
Four QTLs detected for chlorophyll concentration accounted for 53.5% of
the phenotypic variation for this trait and three QTLs for net photosynthesis
accounted for 62.5% of total phenotypic variation. As far as stomatal
conductance is concerned, four QTLs with 61.9% of the phenotypic variation
were detected, whereas predawn water potential was associated with three
QTLs explaining only 34.1% of phenotypic variance.
5.2.6 In vitro Regeneration
The ability to regenerate large number of plants is important for the
development of biotechnological tools such as genetic transformation in
sunflower. In vitro regeneration was investigated in 75 RILs and their parents
(PAC2 and RHA266). The results summarized in Table 5-1 showed that the
six putative QTLs for the number of shoots per plant and seven for shoots
per regenerating explants were detected in cotyledon organogenesis culture
(Flores-Berrios et al. 2000a). The same RILs were also used for somatic
embryogenesis by epidermic layers and four QTLs were identified for the
total number of embryogenic explants, which explained 48% of the
phenotypic variation for this trait (Flores-Berrios et al. 2002b). The above-
mentioned RILs were also used in another experiment in which 12 QTLs
were identified for protoplast division with a total phenotypic variation of
72% (Flores-Berrios et al. 2000c). The results showed that some segments of
the linkage groups l, 15 and 17 are likely to contain genes important for
organogenesis, somatic embryogenesis and protoplast division. The QTLs
identified in these three linkage groups should be involved in cell division
in early events associated with cell differentiation. Genomic regions involved
in somatic embryogenesis have also been identified in PAC2×RHA266 RIL
mapping population, and three QTLs were resolved for the number of
embryogenic explants per 100 explants cultured, (Huang et al. 2007). These
three QTLs explained 38.6% of the phenotypic variation, with LOD scores