Bioscience in brief
Plant genetics and crop breeding
Where do our crops come from? I. Maize
Maize is one of the most important sources of food in the African continent:
in 2010 production in Africa was worth over $US 6 billion (FAO).
Where does maize come from? Maize was domesticated over 6000 years ago in what is now Mexico, from a wild grass called teosinte. The two plants look very different, maize plants having a single tall stalk with multiple leaves while teosinte being a short, bushy plant. The kernels are also very distinct: maize has several rows of soft, starchy kernels arranged along a cob, while teosinte kernels are enclosed in a thick, hard case, and are arranged on only two sides of a cob that falls apart at maturity.
However, at the DNA level, the two are surprisingly alike: only about 5 genes were responsible for the most notable differences between teosinte and a primitive strain of maize. Why do they look so different? Teosinte evolved to
maximize its reproductive success in natural habitats, not its food value for humans!
The maize flower
In maize, female and male flowers are arranged in groups or clusters (called inflorescences). The male inflorescence (the tassel) develops at the tip of the plant: when mature tassels release the pollen grains (which contain the male sperm cells).
The maize female inflorescences are called ears: these are tightly covered over by several layers of leaves. The only visible part of the female flowers is the pale yellow silk protruding from the leaf whorl at the tip of the ear. The silk is the stigma (the part of the flower that receives the pollen during fertilisation).