Systematics and Evolution of Sorghum Sect. Sorghum (Gramineae)

Abstract

The genus Sorghum Moench is subdivided into sections Chaeotosorghum, Heterosorghum, Parasorghum, Stiposorghum and Sorghum. Section Sorghum includes two rhizomatous species, S. halepense (L.) Pers. (2n = 40) and S. propinquum (Kunth) Hitchcock (2n = 20), as well as the annual S. bicolor (L.) Moench (2n = 20). Sorghum bicolor is divided into subspecies bicolor to include all domesticated grain sorghums, subspecies drummondii (Steud.) de Wet comb. nov. to include stabilized derivatives of hybridization among grain sorghums and their closest wild relatives and subspecies arundinaceum (Desv.) de Wet et Harlan to include the wild progenitors of grain sorghums. Four ecotypes of subspecies arundinaceum are recognized: race aethiopicum of the arid African Sahel. race virgatum of northeastern Africa, race arundinaceum of the African tropical forest, and race verticilliflorum of the African Savanna. The numerous, usually recognized grain sorghums are divided among five basic races, bicolor, caudatum, durra, guinea and kafir, and ten hybrid races that each combine characteristics of at least two of these basic races. Races of grain sorghum are morphologically distinct, and they maintain their unity of type through spacial and ethnological isolation.