The project is focused on the localizeation of loci implicated in adult stage resistance to the septoria disease of wheat (Triticum aestivum), an important disease in Belgium and in Europe. The resistance to this wheat disease at has been chosen for its economic importance; wheat occupies a surface of about 120.000 hectares in Wallonie, 220.000 ha in Belgium and 16 millions ha in Europe. In plant breeding, different specific resistance genes, which are expressed since early stages, are characterized and used in the creation of resistant varieties. However, each of these genes confers a resistance to a very specific race and its action can be quickly by-passed by new pathogen races apparition. On the other hand, some varieties cultivated during a large number of years and in many places present a long term resistance. This resistance, which express itself at adult stage, is of quantitative type and is controlled by several genes acting jointly (Quantitative trait loci or QTL). The utilization of naturally and lastingly resistant wheat varieties would permit to decrease the number of fungicide treatments applied during culture and would be therefore of ecological and economic profits. Besides, the definition of loci implied in these aspects and of associated molecular markers would permit to select plants more quickly and efficiently at a precocious stage of the selection, independently of external conditions.
Objectives
We will display loci implied in the adult resistance to the wheat septoria disease. We will build up genetic maps of wheat populations segregating for the resistance, using the various molecular markers (microsatellites, EST, AFLP, RFLP). The necessary genetic material and the different molecular markers are available. The development of precise expanded genetic maps and statistical tools will permit the localization of loci implied in the quantitative characters (QTL). The finding of tight links between molecular markers and the different QTL or genes will permit to develop a markers assisted selection by (MAS) and therefore, to follow the introgression of the different genes during the creation of varieties possessing this type of resistance. We will try to analyse the genetic complexity of the quantitative character determinism by searching for the existence of links between the QTLS inferred in these agronomic characters and candidate genes involved into the mechanisms of plant resistance.
Expected results
We will localize the different QTLS linked to the resistance. Molecular markers, microsatellites EST, AFLP and RFLP will be analyzed on the parents of the populations and those permitting to detect a polymorphism will be positioned on the genetic maps. Segregation data of the molecular markers and the evaluated quantitative characters are treated according to different methods; with the softwares Mapmaker QTL and QTL cartographer, as well as by the classical tests (ANOVA, regression). The chromosomal zone map implied in the considered characters will be refined in order to best surround the localization of the QTL put in evidence. Gene candidates which can be involved in resistance mechanisms will also be used as specific probes via PCR amplification and will be localized on maps. We will develop a markers assisted selection by for this resistance character.
Results obtained
Populations segregating for the adult resistance to the septoria disease have been produced by crossings of the varieties Oasis X Renan and Mobil X Hussar. These populations have been fixed by single seed descent (SSD) and have been multiplied in order to obtain enough plant material to perform the molecular analyses and infection tests in the fields. Cartography The development of maps of these populations will be pursued; we will use markers of different type: microsatellites, EST, AFLP, as well as of the RFLP markers. Every marker is first used on the parents of the different populations; and the ones allowing to detect polymorphism are then used on the different members of the population. Segregation data of are dealt with the Mapmaker software in order to construct the maps of the different chromosomes of each population. Phytopathological evaluation The adult resistance to disease in the different fixed populations has been evaluated. Lines of the different populations are sowed in seed-hole in the field. Different parameters of infection have been appraised and a visual global score of resistance was assigned. These observations will be repeated in different places and different years.
Partners
This work is carried out in collaboration with A. Dekeyser, Walloon Centre of agronomic Researches.
