Biology Reference
In-Depth Information
3.4.2.3 GMendel
GMendel is a useful tool for constructing linkage maps from both molecular
marker and Mendelian phenotypic data. The unique feature of GMendel is
its multiple pairwise locus ordering methods. In GMendel, a simulated
annealing algorithm is programmed for fast linkage analysis runs, and
Monte Carlo and bootstrap methods are employed to validate the order of
mapped markers (Holloway and Knapp 1993). GMendel has been used by
Gedil et al. (2001), Yu et al. (2003), Slabaugh et al. (2003) and Lai et al. (2005)
in sunflower genome mapping.
3.5 Achievement
During the past 15 years, genome mapping has been an active and highly
successful area in the sunflower research community, including both public
research institutions and proprietary seed companies. Linkage maps of
various types of molecular markers have been constructed from over 20
mapping populations. These maps revealed the genome organization and
expanded our knowledge of this important oil crop. Some representative
maps are discussed below.
3.5.1 RFLP Maps
The first published linkage map of cultivated sunflower was a proprietary
one (Berry et al. 1995). It spanned 1,380 cM on 17 linkage groups and
contained 234 RFLP loci detected by 213 cDNA probes. The mapping
population was an F
2
population of 289 individuals derived from a cross
between two inbred lines, HA 89 and ZENB8. HA 89 is a public sunflower
inbred line released by USDA and ZENB8 is proprietary inbred maintainer
line. Twenty-three of the 234 loci showed significant segregating distortion.
This map was later “joined” with maps constructed from eight other F
2
populations to form a high density, composite map with 635 marker loci
and was 1,472 cM in length (Berry et al. 1996). The second sunflower RFLP
linkage map was published by a French group (Gentzbittel et al. 1995). This
map of 237 loci spanning 1,150 cM and consisting of 16 linkage groups of
more than 20 cM and seven groups of less than 20 cM was constructed from
three F
2
and two BC
1
populations. The length of individual population map
ranged from 71 ((HA 89 x CX) x CX BC
1
) to 763 (PAC2 x RHA 266 F
2
) cM. The
maps from three F
2
populations were further integrated into a composite
map with the maps from four other F
2
populations (Gentzbittel et al. 1999).
Although the length of the individual maps varied from 774 cM to 1,060 cM
with an average of 14 major linkage groups, the composite map (CARTISOL
map) comprised 273 marker loci and had a length of 1,573 cM. A third
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