What is Sorghum?
Sorghum bicolor is a robust and genetically variable member of the grass family which looks very similar to maize and sugar cane. Sorghum has strong stems and ranges in height from less than 1 m to 4 m. Stems can be juicy or dry, sweet or bitter. Leaves are arranged alternatively and have prominent midveins and parallel lateral veins. Long overlapping sheaths are attached at the nodes.

History and Taxonomy
A sorghum collection was first described by Linnaeus in 1753 under the name Holcus. However, in 1794 Moench re-classified this collection as a separate genus: Sorghum (Celarier, 1959). The genus Sorghum belongs to the tribe Andropogoneae, and is divided into three species (de Wet, 1978): Sorghum halepense (L.) Pers., which is a native perennial of southern Eurasia east to India; S. propinquum (K.) Hitch., which is a native perennial of Sri Lanka and southern India, and from Burma eastward to the islands of south-eastern Asia; S. bicolor (L.) Moench (Plate), which includes all annual taxa of the section Sorghum as recognised by Snowden (1936, 1955). S. bicolor encompasses all the domesticated taxa, a widely distributed and ecologically variable African complex, and stabilised weedy derivatives derived from inter-breeding between domesticated sorghums and their closest wild relatives.

Evolution and Domestication
Cultivated sorghums were domesticated from wild Sorghum bicolor subsp. arundinaceum around 3000 years ago in the north-east quadrant of Africa (Snowden, 1936; Evelyn, 1951; Doggett 1965, 1988). Cultivated sorghums are divided into five basic races: bicolor, guinea, caudatum, kafir, and durra, and ten hybrid races that combine the characteristics of any two or more basic races (Harlan and de Wet, 1972). There is an extremely large amount of variation between the cultivated taxa in the species S. bicolor. In his definitive classification of the cultivated races of sorghum, Snowden (1936) listed 31 species, 158 varieties, and 523 forms. All of these can be placed into one of the five basic races or 10 hybrid races.

The different races of sorghum occupy a wide range of ecological habitats, having been selected for specific local environments. As such, each race tends to have a defined geographical distribution, with intermediate races occurring along the edges of these zones. Guinea is the dominant race in the West African savannah from Senegal to western Chad. Moving eastward, it is replaced first by guinea-caudatum and then by caudatum. Guinea-kafir is found in East Africa where both guinea and kafir are also grown. Durra-caudatum is the major race in northern Nigeria with a belt of durra to the north in Niger, and caudatum to the south and east (Harlan and de Wet, 1972).