Mapping and Tagging of Simply Inherited Traits - Genetics, Genomics and Breeding of Crop Plants - page 121

Table 4-1 contd....
Trait Gene/locus Linkage Population/s, References

group (LG) line/s

Tocopherol cyclase LG 8 R112 x LG24, Hass et al. 2006

RHA280 x RHA801

Tocopherol mutant g LG 8 R112 x LG24, Hass et al. 2006

Tocopherol mutant d LG 4 R112 x LG24, Hass et al. 2006

MBPQ/MSBQ-MT LG 1 NMS373 x SRA16, Tang et al. 2006b

RHA280 x RHA801

Tocopherol mutant m LG 1 NMS373 x SRA16 Tang et al. 2006b

Tph2 LG 8 CAS-12 x IAST-540 Garcia-Moreno et

al. 2006

Tph1 LG 1 CAS12 x T589 Vera-Ruiz et al.

2006

4.2 Disease Resistance

4.2.1 Resistance to Downy Mildew
As resistance to different races of downy mildew belonged to the first-mapped
traits in sunflower, mapping of downy mildew resistance genes will be
described in more detail. Downy mildew caused by Plasmopara halstedii
(Farl.) Berl and de Toni is one of the destructive diseases in cultivated
sunflower ( Helianthus annuus L.). Vranceanu and Stoenescu (1970) described
the first gene conferring resistance against downy mildew ( Pl 1 ). They
identified this gene as dominant and independent. In the following years,
further Pl genes were discovered from different sources and were
incorporated into the breeding material. Some of these Pl genes confer
resistance against only one race of the pathogen (e.g., Pl 1 against race 100),
others are effective against few (e.g., Pl 2 ) or all known races (e.g., Pl 8 and
Pl ARG ). In the last few years, new races of P. halstedii emerged in the cultivation
areas of sunflower (Tourvieille de Labrouhe et al. 2000; Molinero-Ruiz et al.
2002). Moreover, some races developed tolerance to the fungicide metalaxyl
(Albourie et al. 1998; Spring et al. 2006), which is the only effective plant
protecting agent against this disease. For these reasons, a constant search
for new Pl genes and the elucidation of the nature of resistance is imperative.
The discovery of linkage between resistance genes and molecular markers
in order to be able to use these purposefully and durably in plant breeding
is of high importance, for example for pyramiding of several resistance
genes (Brahm et al. 2000).
Using bulked segregant analysis (BSA; Michelmore et al. 1991),
Mouzeyar et al. (1995) mapped Pl 1 as the first Pl locus on group 1 of the
CARTISOL map (Gentzbittel et al. 1995), which is identical with LG 8 of the
public SSR map. They could identify two polymorphic restriction fragment
length polymorphism (RFLP) markers (SUN17, SUN124) and screened them
against 135 F 2 plants derived from a cross between GH x RHA266 ( Pl 1 ). The