|Guill, Katherine - Kate|
|Oropeza Rosas, Marco|
|Holland, Jim - Jim|
|Buckler, Edward - Ed|
Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2009
Publication Date: 8/7/2009
Citation: Mcmullen, M.D., Kresovich, S., Sanchez-Villeda, H., Bradbury, P., Li, H., Sun, Q., Flint Garcia, S.A., Thornsberry, J., Acharya, C., Bottoms, C., Brown, P., Browne, C.J., Eller, M.S., Guill, K.E., Harjes, C., Kroon, D., Lepak, N.K., Mitchell, S., Peterson, B.E., Pressoir, G., Romero, S.M., Oropeza Rosas, M., Salvo, S.A., Yates, H., Hanson, M., Jones, E., Smith, S., Glaubitz, J., Goodman, M., Ware, D., Holland, J.B., Buckler Iv, E.S. 2009. Genetic Properties of the Maize Nested Association Mapping Population. Science. 325:737-740. Interpretive Summary: Understanding the genetic basis of agronomic traits for maize (corn) is essential to efforts at predictive crop improvement, yet only slow progress has been made in identifying the genes controlling these agronomic traits despite considerable effort. A major reason for this slow progress is limitations in the scope of genetic diversity and resolution power in the currently available genetic mapping resources. In this manuscript we describe the construction and genetic properties of a novel genetic resource for quantitative trait analysis in corn. We have designated this genetic resource as the nested association mapping (NAM) population. The genetic structure of the NAM population is a reference design of 25 families of 200 recombinant inbred lines per family with the parents selected to capture the maximum amount of genetic diversity. Using this population, we have developed the highest resolution genetic map for any plant species. The NAM population is being adopted by maize scientists as the central community genetic resource for trait analysis. The tremendous amount of randomly segregating genetic diversity captured in the NAM population makes it uniquely suited for assaying the full range of phenotypes and agronomic traits in maize and for high resolution mapping of their underlying genetic factors.
Technical Abstract: Maize is one of the world’s most diverse species, and this variation can be used to understand the molecular basis of phenotypic variation and to improve agricultural efficiency and sustainability. To access this genetic variation, 25 diverse inbred maize lines were crossed to the B73 reference line, and 5000 recombinant inbred lines were created and genotyped. This population provides unique opportunities to evaluate the effects of intraspecific genetic diversity on recombination and allele segregation. A total of 136,000 recombination events were captured in the construction of this population. Substantial genetic variation for recombination frequencies was observed among families, influenced by local (cis) genetic variation. Evaluation of recessive genetic load in this population revealed evidence for numerous minor single locus effects but little two locus segregation distortion, indicating a limited role for genes with large effects and epistatic interactions on fitness. We demonstrated excess residual heterozygosity in pericentromeric regions, suggesting that selection in inbred development has been less efficient in these regions, likely due to their reduced recombination frequency. This implies that pericentromeric regions may contribute disproportionally to maize heterosis. This population captures much of the variation of a highly diverse species and provides power to detect even subtle genetic effects, making it the most powerful public resource for studying genetic diversity of any species and a foundation for understanding phenotypic variation in maize.