Spontaneous Hybridization between Maize and Teosinte

Norman C. Ellstrand, University of California - Riverside
Lauren C. Garner, California Polytechnic State University - San Luis Obispo
Subray Hedge, University of California - Riverside
Roberto Guadagnuolo, Universite de Neuchatel
Lesley Blancas, University of California - Riverside

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Copyright © 2007 Oxford University Press. This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Journal of Heredity following peer review. The definitive publisher-authenticated version is available online at http://dx.doi.org/10.1093/jhered/esm002.

Abstract

The closest wild relatives of maize, Zea mays ssp. mays are various Zea taxa known as ‘‘teosinte.’’ Hybrids between maize and the teosinte taxon, Zea mays ssp. mexicana, often occur when the 2 are sympatric in Mexico. Measuring the spontaneous hybridization rate of the 2 taxa would shed light on the mechanisms contributing to the evolution and persistence of these hybrid swarms. We conducted a series of field experiments in Riverside, CA, to measure the natural hybridization rates between maize and 2 teosinte taxa, Z. m. ssp. mexicana and Zea mays ssp. parviglumis. We planted teosinte within and near maize plantations. Hybrids were identified by progeny testing for a maize-specific herbicide resistance allele and a teosinte-specific allozyme allele. Hybridity was confirmed by growing putative hybrid progeny to maturity to evaluate whether they had the characteristic morphology of maize X teosinte hybrids.We found that maize and Z. m. ssp. mexicana naturally hybridize at a low rate (<1%), whereas Z. m. ssp. parviglumis hybridizes with the crop at a high rate (>>50%).