Location: Corn Host Plant Resistance ResearchTitle: Gene Flow Among Different Teosinte Taxa and Into the Domesticated Maize Gene Pool Author
Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2010
Publication Date: 3/1/2011
Citation: Warburton, M.L., Wilkes, G., Taba, S., Charcosset, A., Mir, C., Dumas, F., Madur, D., Dreisigacker, S., Bedoya, C., Prasanna, B.M., Xie, C.X., Hearne, S., Franco, J. 2011. Gene flow among different teosinte taxa and into the domesticated maize gene pool. Genetic Resources and Crop Evolution. 58:1243-1261. Interpretive Summary: In this article, we have reviewed the genetic contribution of several species and subspecies of teosinte, the wild relatives of corn, to corn evolution. Our unique approach looks at 15 individuals in each population of corn and teosinte and measures genetic diversity and relationships between populations using molecular genetic markers. All previous articles that we are aware of use considerably fewer individuals (sometimes only one) so cannot have measured well the within population variation from each species. In addition, we look at 100 populations of corn and all but one teosinte subspecies. We believe our generous sampling shows a better picture of gene flow between species. Indeed, we show evidence of geneflow from other teosinte species than the ancestral subspecies into corn, and between teosintes. We believe this to be a critically important result, for an understanding of corn evolution, corn improvement via plant breeding and introgression from wild species, and the importance of conservation of all teosinte taxa.
Technical Abstract: Maize (Zea mays ssp. mays) was domesticated from one wild species ancestor, the Balsas teosinte (Zea mays ssp. parviglumis) about 9000 years ago. Higher levels of gene diversity are found in teosinte taxa compared to maize following domestication and selection bottlenecks. Diversity in maize can be increased via gene flow from teosinte, which has certainly occurred from various taxa, but the rate of flow from different teosinte taxa and the final impact on maize evolution has been difficult to measure. One hundred populations from six Zea taxa, both domesticated (maize) and wild (teosinte), including domesticated landraces from Asia, Africa, and the Americas, were genotyped with 17 SSR markers using 15 individuals per population. Overall levels of diversity were high, and populations could be distinguished based on markers. Relationships between populations followed most published reports, or can now help resolve previously conflicting reports. Gene flow into maize from different teosinte groups, and gene flow between different teosintes, was estimated. Evidence for contributions from the Balsas teosintes and from Z. mays ssp. mexicana (“Chalco” races) to the maize gene pool was found, as well as from Chalco into ssp. mexicana race “Durango” and Z. mays ssp. huehuetenengensis. These contributions are almost certainly the result of post-domestication (and ongoing) exchanges. This information will give more impetus to in situ conservation of teosinte species, and use of these teosintes to continue to direct the evolution of maize, especially in response to new diseases, insect pests, and other biotic and abiotic stresses.