La sélection assistée par marqueurs

Chantereau Jacques. 2001. La sélection assistée par marqueurs. In : Les insectes ravageurs du sorgho en Afrique de l'Ouest et du Centre : actes = Insects pests of sorghum in West and Central Africa : proceedings. Ratnadass Alain (ed.), Ajayi Olupomi (ed.), Marley Paul S. (ed.), Akintayo Inussa (ed.). CIRAD, ROCARS, ICRISAT. Montpellier : CIRAD, 108-116. ISBN 2-87614-446-8 Atelier de formation sur les insectes ravageurs du sorgho, Samanko, Mali, 14 Octobre 1996/23 Octobre 1996.

Titre anglais : Marker assisted selection

Résumé : The recent evolution of plant breeding is largely due to the development of molecular (DNA) marker techniques, such as the ones based on Restriction Fragment Length Polymorphism (RFLP), and Random Amplification Polymorphic DNA (RAPD), which use single locus co-dominant, and multilocus random dominant markers, respectively. The RFLP technique is described as an example to illustrate the different aspects of mapping. DNA is first extracted, then digested using restriction enzymes with specific cutting sites (which results in variability in fragment length in case of polymorphism/sequence changes), then run on an agarose gel for size-based electrophoretic separation of fragments; the DNA is then transferred on to a nylon membrane and incubated in a solution with a radio- or chemical-labeled probe, so as to have the probe hybridized to the membrane, and the spot where the probe was fixed visualized. A QTL is a short genome fragment involved in the variation of a quantitative trait, which is localized using molecular marker techniques. QTL identification implies the analysis of the relationship between the polymorphism of a given marker within particular genotypes, and the variation of a quantitative character in the same genotypes. If a given phenotypic trait is tightly linked to a given molecular marker, the genetic segregation of the gene of interest can be determined by the presence or absence of this molecular marker, instead of the phenotype, using a process referred to as Marker-Assisted Selection (MAS). The progress of these genes through the generations can be followed simply by early screening of DNA samples from seedlings, which does not require full-scale field screening, thus saving time and money. The first step of a MAS program is the establishment of a mapping population, which is realized by crossing parent lines that are divergent for the trait considered (e.g. resistance/susceptibility to a parasite), phenotypically as well as in their RFLP markers. Mapping is putting markers in order, indicating the relative genetic distances between them, and assigning them to their linkage group on the basis of the recombination values. Recombinant inbred lines (RIL) can be derived from the F1 population using Single Seed Descent. Single locus co-dominant markers (e.g. RFLP) are well adapted for mapping genes with quantitative effect (QTL) using RILs, and provide reliable results. For a given RIL-based progeny, it is more efficient to maximize the number of genotypes to be characterized, than the number of markers. Given G x E interaction, phenotypic characterization should be repeated over years and/or across locations. Apart from mapping and tagging of genes, RFLP markers can be used for detecting gene introgression in backcross breeding programs.

Mots-clés Agrovoc : Sorghum, sélection, marqueur génétique, adn, RAPD, RFLP, locus, carte génétique

Classification Agris : F30 - Génétique et amélioration des plantes

Auteurs et affiliations

• Chantereau Jacques, CIRAD-CA-CEREALES (MLI)

Source : Cirad - Agritrop (https://agritrop.cirad.fr/478741/)

Métriques

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