Mapping and Tagging of Simply Inherited Traits - Genetics, Genomics and Breeding of Crop Plants - page 127

parasite attacking sunflower were in Russia, and the attack of broomrape
intensified at the beginning of the 20th century when all cultivars grown
suffered large scale losses (Miller and Fick 1997). Broomrape is a serious
pest of cultivated sunflower in Europe, especially southern Europe, the
Balkans, and the Mediterranean (Parker and Riches 1993).
Because O. cumana has a broad host range and produces an
extraordinarily large number of small, long-lived, facilely dispersed seeds,
control through crop management has been difficult. The most economical
and effective means of controlling sunflower broomrape is by growing
resistant cultivars (Sukno et al. 1999; Lu et al. 2000). While various
genetically simple and complex sources of Orobanche resistance have been
described in sunflower, the most important and widely used are single
dominant genes (for references see Tang et al. 2003).
As a first report on molecular markers linked to a broomrape resistance
gene, Lu et al. (2000) identified five sequence characterized amplified region
(SCAR) markers and one RAPD marker linked to the gene Or 5 which confers
resistance to race E of broomrape. Their investigation based on two F 2
populations with the resistant parent line RPG01. As a next step Lu et al.
(1999) could integrate their markers in group 17 of the CARTISOL RFLP
map published by Gentzbittel et al. (1995). Tang et al. (2003), using BSA,
placed the Or 5 gene in a telomeric region of LG 3 with the closest SSR marker
(ORS1036) being 6.2 cM proximal to the Or 5 locus. In a QTL study for
broomrape resistance Pérez-Vich et al. (2004a) identified one major QTL
( or3.1 ) affecting race E resistance that was stable over different experiments
carried out in different environments and with different race E broomrape
populations. The map position of the QTL or3.1 detected on top of LG 3
corresponds to the region where Or 5 was mapped by Tang et al. (2003).
A study with molecular, biochemical, proteomic and histochemical
approaches to investigate the resistance mechanisms of sunflower inbred
line LR1 was published by Letousey et al. (2007). LR1 exhibits strong
polygenic resistance occurring at different stages of O. cumana development.
The resistance of line LR was mainly characterized by O. cumana necrosis,
which took place soon after attachment. The results of this study suggested
that the resistant genotype LR1 reacts by strong induction of salicylic acid
and jasmonate pathways and a later reaction was the induction of ethylene
pathways. Two pathogenesis-related (PR) genes ( chit . and def .) were also
induced during the later stages of the interaction. However, just before the
first O. cumana necrosis, resistant roots exhibited a transient quasi-total
repression of most of the studied genes. Only HaDef1 showed a strong
induction. An explanation of this phenomenon could be the setting up of a
mechanism of regulation that organized the overall response towards a
more specific and effective pathway (Letousey et al. 2007). HaDef1 , originally
named def. by Hu et al. (2003) has been described as a leaf molecular marker