Anthracocystis ehrenbergii

Anthracocystis ehrenbergii is a specialized phytopathogenic fungus belonging to the order Ustilaginales. Systematically, it is classified within the kingdom Fungi, phylum Basidiomycota, and the genus Anthracocystis. This organism was historically recognized in agronomic literature under the name Sphacelotheca sorghi, but taxonomic revisions have recently redefined its classification.

This pathogen is the primary causal agent of sorghum covered smut (or grain smut). It exclusively targets various species of the genus Sorghum, including grain sorghum and Sudan grass. The infection manifests as the replacement of kernels with fungal sori (smut balls), which contain a dense mass of black teliospores, effectively destroying the yield of the affected plants.

The biological cycle of the pathogen is closely tied to the host's development. Infection primarily occurs during seed germination, as spores adhering to the pericarp or present in the soil germinate and penetrate the coleoptile of the seedling. Once inside, the fungus grows systemically within the plant tissues, eventually colonizing the floral tissues to produce new generations of spores by the time the plant reaches the heading stage.

Environmental factors, specifically soil temperature and moisture levels, significantly influence disease incidence. Infection is most prevalent when soil temperatures range between +18°C and +25°C at the time of sowing. Dry conditions or delayed emergence can increase the window of susceptibility, allowing the fungus to successfully colonize the seedling and establish a systemic infection.

The economic impact of the disease is severe, often resulting in complete loss of infected panicles and reduced grain quality. Controlling the pathogen requires a multi-faceted strategy focused on prevention and field management:

• Systemic seed treatment with fungicides prior to planting.
• Rotation with non-host crops to reduce soil-borne inoculum levels.
• Selection of resistant or tolerant sorghum cultivars.
• Proper disposal of crop residues to break the disease cycle and limit the spread of spores.