Track 2-12: Control and Management of Weeds and Diseases of Grass and Forage Systems
Description
Resistance to Phytophthora medicaginis is an essential attribute to incorporate into lucerne (Medicago sativa) cultivars which are likely to be grown on heavy soils or in conditions where the soil remains excessively wet for prolonged periods. Current breeding strategies rely on recurrent phenotypic selection to maintain adequate levels of resistance in newly developed synthetic cultivars. However, little is known about the source or mechanism(s) of genetic resistance operating in the cultivar. A genetic linkage map was generated from a tetraploid M. sativa population using SSR markers anchored to existing genetic and physical maps. Large effect QTL were identified on linkage groups 2, 5, 6 and 7, each of which contributed between 11-30% of the phenotypic variation. Evaluation of the marker-trait associations in another sampling of the same population was undertaken, using a different isolate of P. medicaginis. The findings indicate that in the lucerne genotype examined in this study, a network of interactions involving at least three common loci, contribute to resistance to P. medicaginis. An alignment of the resistance loci identified in this study with those previously identified provided a framework for cataloguing the diversity of resistance loci present in lucerne, and will be used to guide future lucerne breeding efforts.
Included in
Development and Validation of Molecular Markers for Phytophthora medicaginis Resistance in Lucerne
Resistance to Phytophthora medicaginis is an essential attribute to incorporate into lucerne (Medicago sativa) cultivars which are likely to be grown on heavy soils or in conditions where the soil remains excessively wet for prolonged periods. Current breeding strategies rely on recurrent phenotypic selection to maintain adequate levels of resistance in newly developed synthetic cultivars. However, little is known about the source or mechanism(s) of genetic resistance operating in the cultivar. A genetic linkage map was generated from a tetraploid M. sativa population using SSR markers anchored to existing genetic and physical maps. Large effect QTL were identified on linkage groups 2, 5, 6 and 7, each of which contributed between 11-30% of the phenotypic variation. Evaluation of the marker-trait associations in another sampling of the same population was undertaken, using a different isolate of P. medicaginis. The findings indicate that in the lucerne genotype examined in this study, a network of interactions involving at least three common loci, contribute to resistance to P. medicaginis. An alignment of the resistance loci identified in this study with those previously identified provided a framework for cataloguing the diversity of resistance loci present in lucerne, and will be used to guide future lucerne breeding efforts.
