Crop's Wild Relatives: Maize and Teosinte by Dylan Sweetwood - a podcast by Liz Hadly

The Relationship Between Maize and Teosinte
Dylan Sweetwood

You probably already know that maize, or corn, is one of the most culturally and commercially important crops in the world, with hundreds of applications in areas from agriculture to energy. But what you may not know is that teosinte, one of corn’s closest genetic relatives, is currently under threat of extinction. Then again, so are a lot of other plants—why is teosinte worth worrying about? My name is Dylan Sweetwood, and I’m going to talk about the relationship between maize and teosinte and why this relationship is important to preserve.

Humans have grown maize for thousands of years—so long, in fact, that it can no longer reproduce without human cultivation. This long history has resulted in a genetic bottleneck, which means that all modern varieties of corn are genetically indistinguishable. Traditionally, this was considered advantageous, but now scientists believe that genetic diversity is beneficial for crop persistence. Corn’s limited genetic toolkit makes it more susceptible to natural disasters like drought and climate change, which is a big problem for farmers.

Fortunately for the agricultural industry, teosinte, which is usually found growing on the edge of cornfields, hybridizes well with its domestic relative. Hybridization is when two related species swap genes, resulting in a genetic mixture. Maize and teosinte have hybridized naturally for millennia; by hybridizing the two selectively, it would be possible to breed new varieties of maize whose gene pools are diversified and strengthened by teosinte. These genes may offer resistance to natural stressors and sometimes even increase crop yield—something farmers would definitely be happy about.

Unfortunately, natural hybridization is risky. Because maize and teosinte have been hybridizing for so long, their hybrids usually have high fertility rates; farmers often consider these hybrids weeds and they exterminate them, which stops teosinte genes from being passed on to future generations of crop corn. As you might guess, infestation of maize-teosinte hybrids in and around cornfields is actually threatening teosinte because it dilutes the wild type. Teosinte also has a very narrow geographical range, limited to small populations in Central America; because of this, teosinte is more vulnerable in the face of environmental changes and invasive species. The small range of teosinte combined with genetic swamping has pushed this wild species to the brink of extinction.

Today, the teosinte population is less than half of what it was fifty years ago. Controlled hybridization of maize and teosinte could have a lot benefits, like increased hardiness and favorable crop yields. The same holds true of many common crops and their wild crop relatives, but considering how important corn is to humans—and anticipating how much more vital it will be in the future—teosinte preservation is an issue that requires immediate action. Thank you.

References
Haygood, Ralph, Anthony R. Ives, and David A. Andow. 2003. Consequences of Recurrent Gene Flow from Crops to Wild Relatives. Proceedings of the Royal Society B: Biological Sciences 270: 1879-886.

Wilkes, H. G. 1972. Maize and Its Wild Relatives. Science 177: 1071-077.

Album Credit
http://teosinte.wisc.edu/Images_to_download/maize_and_teosinte.jpg

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