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Genus Sorghum in Family Poaceae

In botanical taxonomy, a genus (plural genera) is a rank used to group closely related species within a family. In the hierarchy, genus sits below family and above species.

Genera are defined by shared morphological, anatomical, and genetic characteristics (for example, features of flowers, fruits, seeds, or leaves) that indicate a close evolutionary relationship among the species they contain.

Each genus can include one or more species. Examples include Rosa (roses) and Solanum (nightshades, including tomato and eggplant).

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Genus Description

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Sorghum (Moench) is a genus of about thirty species in the Poaceae family, tribe Andropogoneae, native mainly to sub‑Saharan Africa and South Asia, with some species naturalised in the Americas and Australia. The type species is Sorghum bicolor (L.) Moench, the cultivated grain sorghum (APG IV, 2016; POWO, 2024).

The genus comprises C₄, often rhizomatous or tufted perennials with linear leaves and reduced membranous ligules, bearing panicles of paired spikelets – sessile, fertile and pedicellate, sterile forms. Each spikelet has a hardened lower glume, an upper glume, and a lemma that may be awned or awnless; the ovary is superior and the fruit is a caryopsis with embryo (Clayton & Renvoize, 1982; van Slageren, 2004).

Diversity peaks in the African savanna belt, notably Ethiopia, Sudan and Kenya, with secondary centres in South‑East Asia and northern Australia. Most species occupy open grasslands, woodland edges or seasonally dry habitats up to 2,000 m. Endemism is pronounced: Sorghum plumosum is confined to the Australian monsoon tropics and Sorghum intrans to the Ethiopian highlands (WFO, 2024; Paterson et al., 2009).

Spikelets are wind‑pollinated and caryopses are dispersed primarily by gravity and water, although some taxa have awns that promote short‑range wind transport. The base chromosome number is x = 10; diploid species have 2n = 20 and many cultivated forms are tetraploid (2n = 40) (Paterson et al., 2009).

Taxonomy divides Sorghum into two subgenera: Sorghum (section Sorghum) and Parasorghum (section Chaetosphis), including S. bicolor, S. halepense and S. sudanense in the former, and S. halopithecus and S. propinquum in the latter (van Slageren, 2004; APG IV, 2016). Molecular studies confirm these clades but reveal S. halepense as a hybrid derivative and confirm that Sorghastrum should remain separate (Doebley, 2004). S. plumosum is often treated as a separate section, though phylogenetic signal is weak (WFO, 2024).

Human relevance is dominated by Sorghum bicolor, the fifth‑largest cereal grain for food, feed and bio‑fuel. Sorghum halepense (Johnsongrass) is a serious weed in agricultural systems, while Sorghum sudanense (sudangrass) provides high‑quality forage. Ornamental sorghums with colorful panicles are cultivated for landscaping (FAO, 2020).

Conservation concerns focus on narrow‑range endemics, as habitat loss and over‑grazing threaten African species and drive ex‑situ seed banking. Genomic gaps for wild relatives limit breeding for climate‑resilient crops. Future work should expand sampling of Parasorghum and integrate phenomic data to refine species limits (WFO, 2024; POWO, 2024).

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