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Plant genetics

Exploring the maize of genetic variation

Nature Reviews Genetics volume 10, page 593 (2009)Cite this article

Two approaches are commonly applied for detecting quantitative trait loci (QTLs) — linkage mapping and association mapping — but both have limitations, such as the low resolution of linkage mapping and the low power of association mapping for detecting rare alleles. Buckler, Holland, Kresovich, McMullen and colleagues combined the advantages of both approaches by devising a nested association mapping (NAM) approach. They derived the NAM resource by crossing a common reference maize strain with 25 diverse lines to maximize the allelic diversity captured by NAM, and this process produced ∼5,000 recombinant inbred lines (RILs). The NAM population can be used to detect QTLs by performing linkage mapping using a moderate number of markers, followed by high-resolution association mapping using a high-density marker map. Because the individuals in a particular RIL are almost genetically identical, the phenotype of a given quantitative trait can be scored in multiple individuals with the same genotype in multiple environments, which increases the power of identifying QTLs.

To enable mapping studies and to explore recombination patterns in these lines, the authors created a composite genetic map with an average marker density of 1 SNP per 1.3 cM. By comparing the recombination events in the RILs, they found extensive variation in the recombination frequency across the 25 maize families that constitute the NAM population. Interestingly, the high levels of heterozygosity that were observed near the centromeres suggest a possible explanation for the phenomenon of heterosis, in which crossing two inbred lines improves the fitness of the offspring— the DNA near the centromeres might not be reshuffled as efficiently as the DNA in the rest of the chromosome during inbred development.

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References

ORIGINAL RESEARCH PAPERS

  1. McMullen, M. D. et al. Genetic properties of the maize nested association mapping population. Science 325, 737–740 (2009)

    Article  CAS  Google Scholar 

  2. Buckler, E. S. et al. The genetic architecture of maize flowering time. Science 325, 714–718 (2009)

    Article  CAS  Google Scholar 

FURTHER READING

  1. Mackay, T. F. C. et al. The genetics of quantitative traits: challenges and prospects. Nature Rev. Genet. 10, 565–577 (2009)

    Article  CAS  Google Scholar 

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Authors
  1. Meera Swami
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Swami, M. Exploring the maize of genetic variation. Nat Rev Genet 10, 593 (2009). https://doi.org/10.1038/nrg2659

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  • DOI: https://doi.org/10.1038/nrg2659

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