Objective
To develop a Multi-parental Advanced Generation Intercross (MAGIC) population for B. napus that will combine beneficial alleles controlling tolerance to multiple abiotic and biotic stresses. The population will serve as a resource for researchers and breeders to dissect complex traits and identify lines that are optimally adapted to multiple environments.
Project Description
The challenge of improving Brassica napus for core agronomic traits, such as durable resistance and abiotic stress tolerance, which would provide sustainable yield gains, is limited by both the complexity of the traits and the available genetic variation. Due to its evolution from a limited number of hybridisation events and the strong selection pressures that have been applied during breeding for seed quality traits, the pool of variation available for B. napus, especially spring-type varieties, is incredibly narrow. Novel variation can be found from germplasm collections and such work has identified new sources of resistance for some important pathogens like clubroot, blackleg and sclerotinia, yet combining multiple of these resources with more complex traits, such as abiotic stress tolerance has proved elusive. Further, the diploid progenitors of B. napus can be exploited to capture additional beneficial alleles now lost from the canola gene pool, yet again combining this incredibly diverse material with elite backgrounds can be frustrating and quickly lead to the loss of carefully captured variants. The proposed project will develop a novel germplasm resource that will allow not only the dissection of complex traits but the selection of material combining beneficial alleles controlling both biotic and abiotic stress tolerance. The project will develop a Multi-parent Advanced Generation Inter-cross (MAGIC) population for B. napus. The eight parent population will use four newly developed resynthesised B. napus lines (current CARP project 2023.45 “Capturing ancestral diversity for developing climate ready Canola”) (SaskOilseeds funded), which encapsulate ncredible genetic diversity, and four advanced breeding lines selected based on improved nutrient use efficiency, improved drought tolerance and quantitative sclerotinia and verticillium resistance.
MAGIC populations are composed of recombinant inbred lines (RILs) that are a genetic mosaic of multiple founder parents, in this instance eight parental lines. MAGIC populations show advantages over experimental bi-parental and germplasm populations in combining significant levels of genetic recombination, a lack of genetic structure, and high genetic and phenotypic diversity. The multiple founders enrich MAGIC populations with higher allelic diversity compared to those derived from typical bi-parental crosses, whereas multiple cycles of parental inter-crossing result in a set of rearranged genomes with a high level of fragmentation, giving greater opportunities for recombination and dramatically increasing the power of quantitative trait loci (QTL) detection. Their design makes them fit for both gene mapping and the effective generation of pre-breeding material. They can also be analyzed across a wide range of environments to increase the understanding of gene-environment interactions (G×E) and phenotypic plasticity, providing a permanent resource to study the basis of phenotypic traits. Previously identified QTLs and the novel ones detected in the final MAGIC population can be synergistically exploited to select the best MAGIC RILs as super trait-donor lines, serving as an advanced source for breeding programs to pyramid novel combinations of QTLs. The applicants have previously developed a MAGIC population for Camelina sativa, and have direct experience of genotyping and phenotyping such populations; their experience working with Camelina will inform the work proposed. The output from the Camelina work is currently being drafted for publication, but it proved compelling with regards to development of novel germplasm and the identification of genetic factors controlling a number of important agronomic traits, for which cost-effective molecular markers are being developed, some of this work was presented recently at Brassica 2025. The proposed B. napus population would be genetically and phenotypically characterised providing a fundamental resource for identifying optimal lines adapted to Prairie conditions. The lines would be phenotyped over multiple years (or environments) using both analogue and digital methods; combined with high density genetic markers the population would be ideal for the application of machine learning algorithms to allow the selection of optimal ideotypes carrying beneficial alleles for multiple traits of interest. Canola has been bred to be adapted to our short growing seasons, which has reduced diversity, and consistent yield of the crop is continuously under threat from not only biotic stresses but concomitantly from the increasingly less than optimal environmental conditions. Developing germplasm that attempts to combine optimal alleles for multiple traits will be essential for ensuring the continued success of the crop. The MAGIC population that is being proposed will provide a unique resource that can be exploited not only for genetic dissection of complex traits, but also for the identification of improved germplasm combining optimal alleles for multiple traits, which will be ideal pre-breeding material. The population would be available for screening in multiple environments and would be of value to researchers and breeders alike.
