Abstract
Multiparent advanced generation intercross (MAGIC) populations were recently developed to allow the high-resolution mapping of quantitative traits. We present a genetic linkage map of an elite but highly diverse eight-founder MAGIC population in common wheat (Triticum aestivum L.). Our MAGIC population is composed of 394 F6:8 recombinant inbred lines lacking significant signatures of population structure. The linkage map included 5435 SNP markers distributed over 2804 loci and spanning 5230 cM. The analysis of population parameters, including genetic structure, kinship, founder probabilities, and linkage disequilibrium and congruency to other maps indicated appropriate construction of both the population and the genetic map. It was shown that eight-founder MAGIC populations exhibit a greater number of loci and higher recombination rates, especially in the pericentromeric regions, compared to four-founder MAGIC, and biparental populations. In addition, our greatly simplified eight-parental MAGIC mating design with an additional eight-way intercross step was found to be equivalent to a MAGIC design with all 210 possible four-way crosses regarding the levels of missing founder assignments and the number of recombination events. Furthermore, the MAGIC population captured 71.7% of the allelic diversity available in the German wheat breeding gene pool. As a proof of principle, we demonstrated the application of the resource for quantitative trait loci mapping analyzing seedling resistance to powdery mildew. As wheat is a crop with many breeding objectives, this resource will allow scientists and breeders to carry out genetic studies for a wide range of breeder-relevant parameters in a single genetic background and reveal possible interactions between traits of economic importance.
Highlights
IntroductionThe detection of quantitative trait loci (QTL) is no longer limited by the availability of genetic marker information and genotyping throughput (Mammadov et al, 2012; Chen et al, 2014; He et al, 2014; Unterseer et al, 2014; Cui et al, 2017), but rather by the genetic material employed (Flint-Garcia et al, 2003; Zhu et al, 2008; Asimit and Zeggini, 2010; Gibson, 2012)
Five hundred sixteen lines were advanced to F6:8 generation and a number of 394 lines were selected based on sufficient seed availability for field trials and suitability for experiments in the agricultural environment
As multiparent advanced generation intercross (MAGIC) designs combine the genetic material of several founders, it is possible to investigate multiple traits simultaneously which is usually limited in biparental populations when adapted germplasm is used
Summary
The detection of quantitative trait loci (QTL) is no longer limited by the availability of genetic marker information and genotyping throughput (Mammadov et al, 2012; Chen et al, 2014; He et al, 2014; Unterseer et al, 2014; Cui et al, 2017), but rather by the genetic material employed (Flint-Garcia et al, 2003; Zhu et al, 2008; Asimit and Zeggini, 2010; Gibson, 2012). In MAGIC designs, multiple inbred founders are intercrossed several times in a well-defined order to combine the genetic material of all the founders in a single line (Cavanagh et al, 2008). This leads to highly diverse genotypes each with a unique mosaic of founder alleles. It is expected that a higher number of parents and initial crosses will result in a better dissection of complex traits (Huang et al, 2012) This implies more time and higher costs for population creation. No study has been published investigating a MAGIC population design that involved a greatly reduced number of overall crossings
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