Biology Reference
In-Depth Information
3.5.4 TRAP Maps
Hu et al. (2004a) described a TRAP marker map constructed with 129 RILs
derived from the cross 83HR4
RHA 345. The map consisted of 160 markers
on 17 linkage groups plus four pairs of linked markers with a total length of
1,140 cM. These markers were amplified with 38 primer combinations in 23
sets of PCR. To demonstrate the applicability of TRAP in rapid genome
mapping, Hu (2006) added 183 TRAP markers to the public SSR map (Tang
et al. 2002) and defined 21 of the 34 linkage group ends by using 94
individuals of the RIL mapping population developed by Steven Knapp's
laboratory and nine fixed primers containing the conserved
Arabidopsis
-
type telomeric repeats (Hu 2006). An additional 220 TRAP markers were
integrated to the same map and expanded the length from 1,523 to 1,920 cM
(Hu et al. 2007). These markers were amplified by fixed primers designed
against selected sunflower ESTs showing homology with components of
plant disease resistance genes, homeobox genes, and other functional genes.
It is worth mentioning that seven polymorphic markers amplified by the
fixed primer designed against a sunflower EST that has homology with
RPS2 were mapped. The mapped positions of two markers, TRAP018749
and TRAP017445, were close to HaRGC1 on LG8 and Ha-1W41 on LG13,
respectively. Both HaRGC1 and Ha-1W41 were mapped to the regions
conferring resistance to different races of downy mildew (Slabaugh et al.
2003). These results suggested that TRAP has the potential to target genomic
regions harboring functional genes controlling the phenotype of interest.
Figure 3-1 shows the public sunflower linkage map. TRAP has been used to
map important traits of sunflower such as nuclear male sterility (Chen et al.
2006), ray flower color gene (Yue et al. 2008b), apical branching gene (Rojas-
Barros et al. 2008), and
Sclerotinia
head rot resistance QTL (Yue et al. 2008a).
3.6 Published Sunflower Linkage Maps
Table 3-1 summarizes the published sunflower maps with various types of
markers. The earlier mapping populations were developed solely for
mapping purposes and the parents were chosen based on the highest
polymorphism level in preliminary screening with molecular markers
(Gentzbittel et al. 1995; Jan et al. 1998). Later the mapping populations were
developed from two parental lines showing differences in disease resistances
or important agronomic traits for the purpose of mapping QTLs underlying
these traits (Bert et al. 2004; Micic et al. 2004; Rönicke et al. 2005;
Poormohammad et al. 2007; Yue et al. 2008b).
It is worth mentioning that the earlier RFLP marker maps were
independently constructed and comparisons between maps were not
possible because there were no common markers among the maps. A total of
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