Genetic diversity of maize

In contrast to the 1970s, current varieties of maize are extremely diverse. There are over 700 different commercial hybrids of maize grown in the U.S. each year now. Compared to the genetic diversity found among all humans, maize contains 20 times the amount of diversity (as measured by nucleotide differences). This is comparable to the diversity found between humans and chimpanzees. So think of it: any two maize lines are significantly more different genetically than a human and a chimpanzee!

Conserving genetic diversity

Around the world scientists are taking care to save genetic diversity by setting aside seeds (and in some cases DNA and/or whole plants) and storing them for future use. These are called germplasm banks or sometimes genebanks. Farmers and plant breeders can request seed of plants they are interested in. For example, the United States Department of Agriculture maintains the National Plant Germplasm System (http://www.ars-grin.gov/npgs/) and the Consultative Group on International Agricultural Research maintains centers around the world (http://www.cgiar.org/).

The saved germplasm includes not only the relatively few species that we currently use for food but also any plants that can be found in nature. Many of these are wild relatives of our food crops that may have important qualities as yet unknown, for example medicinal uses or genes that confer resistance to plant diseases.

One of the largest seed storage facilities in the world is the Kew Millenium Seed Bank Partnership (http://www.kew.org/msbp), located in the UK. Another is the Svalbard Global Seed Vault, an underground facility located on the Norwegian island of Spitsbergen.