Abstract
SummaryMultiparent Advanced Generation Intercross (MAGIC) mapping populations offer unique opportunities and challenges for marker and QTL mapping in crop species. We have constructed the first eight‐parent MAGIC genetic map for wheat, comprising 18 601 SNP markers. We validated the accuracy of our map against the wheat genome sequence and found an improvement in accuracy compared to published genetic maps. Our map shows a notable increase in precision resulting from the three generations of intercrossing required to create the population. This is most pronounced in the pericentromeric regions of the chromosomes. Sixteen percent of mapped markers exhibited segregation distortion (SD) with many occurring in long (>20 cM) blocks. Some of the longest and most distorted blocks were collinear with noncentromeric high‐marker‐density regions of the genome, suggesting they were candidates for introgression fragments introduced into the bread wheat gene pool from other grass species. We investigated two of these linkage blocks in detail and found strong evidence that one on chromosome 4AL, showing SD against the founder Robigus, is an interspecific introgression fragment. The completed map is available from http://www.niab.com/pages/id/326/Resources.
Highlights
Multiparent mapping populations are being widely developed in plant species, and combine high genetic recombination with high diversity
The Multiparent Advanced Generation Intercross (MAGIC) approach was first advocated for crops in 2007 (Cavanagh et al, 2008; Mackay and Powell, 2007) and MAGIC populations have subsequently been developed in a range of species, such as rice (Bandillo et al, 2013), barley (Sannemann et al, 2015), tomato (Pascual et al, 2015) and wheat (Huang et al, 2012; Mackay et al, 2014; Milner et al, 2015; Thepot et al, 2015)
Multiparent Advanced Generation Intercross populations are multifounder equivalents of the advanced intercross introduced by Darvasi and Soller (1995) and are closely related to the heterogeneous stock and composite cross-populations used in mouse genetics (Mott et al, 2000; Threadgill and Churchill, 2012)
Summary
Multiparent mapping populations are being widely developed in plant species, and combine high genetic recombination with high diversity. Multiparent Advanced Generation Intercross populations are multifounder equivalents of the advanced intercross introduced by Darvasi and Soller (1995) and are closely related to the heterogeneous stock and composite cross-populations used in mouse genetics (Mott et al, 2000; Threadgill and Churchill, 2012). They are created by several generations of intercrossing among multiple founder lines leading to greater accumulation of recombination events and greater mapping precision. A MAGIC population founded from good representation of a breeder’s gene pool offers the opportunity to explore patterns of genomic diversity in that gene pool, such as identifying linkage blocks under fertility or viability selection and locating introgression fragments introduced from other species in the breeding process
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