Sorghum

Sorghum bicolor

1. Identification and origin

Sorghum [Sorghum bicolor (L.) Moench] is an annual grass of the Poaceae family, cultivated for the production of grain, forage, silage and biomass. The species originates from Northeast Africa, where it was domesticated more than 5,000 years ago, subsequently spreading to tropical and subtropical regions. It is currently one of the main cereal crops in semi-arid environments owing to its high drought tolerance.

2. Economic importance

Sorghum is used for human food, the production of animal feed, silage, green forage and as a raw material for bioenergy. The grain is rich in starch and has good digestibility, being important in agricultural systems with low water resources. In Mediterranean regions, sorghum has gained relevance as an alternative to maize under conditions of water scarcity. Some varieties are used in the production of syrup, fermented beverages and industrial products.

3. Botanical characterisation

Sorghum is an annual plant of variable size (1–4 m), with an erect and robust stalk. The leaves are broad, alternate, with a membranous ligule. The inflorescence is a terminal panicle, whose shape varies between compact and open, depending on the cultivar. The grains are small, globose, of variable colour (white, yellow, red, brown). The root system is deep and highly efficient in the exploitation of water, conferring great resistance to water stress.

4. Edaphoclimatic requirements

Sorghum adapts to hot and dry climates, with optimal temperatures between 25 and 30 °C. It is one of the most drought- and heat-tolerant cereal crops. It prefers well-drained soils of medium texture, with a pH between 5.5 and 7.5. It tolerates moderately saline soils and conditions of low fertility better than maize. The crop responds well to nitrogen fertilisation and to weed control in the early stages.

5. Main pests

• Caterpillars (Spodoptera frugiperda, Helicoverpa armigera) — leaf damage and damage to panicles
• Sorghum shoot fly (Atherigona soccata) — destruction of the apical meristem and abnormal tillering
• Aphids (Melanaphis sacchari, Rhopalosiphum maidis) — sap sucking, sooty mould and transmission of viruses
• Stink bugs (Nezara viridula) — damage to panicles and developing grains
• Thrips (Frankliniella schultzei) — damage to young leaves and panicles

6. Main diseases

• Anthracnose (Colletotrichum sublineola) — leaf spots and necrosis
• Downy mildew (Peronosclerospora sorghi) — chlorosis, streaks and leaf deformations
• Rust (Puccinia purpurea) — leaf pustules and reduced photosynthesis
• Stalk rots (Fusarium spp., Macrophomina phaseolina) — lodging of stalks and decline
• Sorghum smut (Sporisorium sorghi) — deformed panicles and yield loss

7. General crop management

Sorghum management is based on the choice of cultivars adapted to the cycle and local climatic conditions, on establishment in well-drained soils and on rigorous control of weeds in the early stages. Fertilisation should be balanced, with attention to nitrogen and potassium. The monitoring of caterpillars, aphids and downy mildew is essential, especially in periods of heat and humidity. Crop rotation reduces the pressure of soil diseases and specific pests. Harvesting should be carried out when the grains reach physiological maturity and adequate moisture for storage.

Bibliographic references

• EPPO Global Database – Sorghum bicolor
• CABI – Crop Protection Compendium – Sorghum bicolor
• Paterson, A. H., et al. (2009). The Sorghum bicolor genome and the diversification of grasses. Nature, 457, 551–556.
• Boyles, R. E., et al. (2019). Genetic architecture of grain yield in sorghum. The Plant Genome, 12, 1–15.
• Mace, E. S., et al. (2013). Whole–genome sequencing of sorghum provides insights into the diversification of a C4 crop. Nature Communications, 4, 2320.