Anthracocystis ehrenbergii

Anthracocystis ehrenbergii is a basidiomycete fungus responsible for covered kernel smut in sorghum. Historically classified under the genus Sphacelotheca, it is now assigned to the family Anthracocystaceae.

This pathogen is an obligate parasite that specifically infects the ovaries of sorghum plants, disrupting seed development. It is highly adapted to the host's life cycle.

The fungus produces teliospores, which serve as the primary inoculum. These spores are robust and can persist in soil or adhere to the surface of harvested seeds for extended periods.

Identification often requires careful inspection of the seed heads during maturation, as the pathogen's presence is hidden until the internal tissues are transformed into spores.

Molecular techniques, including PCR-based assays, have been developed to detect and distinguish A. ehrenbergii from other related smut species found in cereal crops.

The primary host for this fungus is Sorghum bicolor. It affects both cultivated grain sorghum and various wild relatives, often causing significant regional losses.

Infection leads to the replacement of healthy grain kernels with sori—pathological growths containing a black, powdery mass of teliospores encased in a membrane.

Economic damage is twofold: direct loss of marketable grain yields and secondary losses due to the contamination of otherwise healthy seed lots with fungal spores.

The pathogen does not usually kill the entire plant, but it severely impacts the reproductive output, rendering the grain inedible and unfit for commercial processing.

In areas with high disease pressure, consistent yield reductions necessitate the mandatory use of chemical seed treatments to ensure economic viability for farmers.

Symptoms are most visible during the grain-filling stage, where infected ovaries swell and become elongated, cylindrical sori protruding from the glumes.

The sori remain covered by a thin, greyish membrane for a period before rupturing to release the dark brown masses of spores onto the field or harvesting equipment.

Unlike loose smut, where the entire panicle is destroyed, Anthracocystis ehrenbergii typically leaves the rest of the sorghum panicle intact, creating a mixture of healthy and infected grains.

Field inspections should focus on the presence of abnormally shaped, discolored grains that lack the typical hardness and luster of healthy sorghum seeds.

Visible signs of infection may be less obvious in early stages, making it crucial to observe the crop carefully as it transitions from flowering to maturity.

Effective control relies heavily on seed disinfection. Systemic fungicide treatments are the standard practice to neutralize spores located on the seed surface and prevent seedling infection.

Crop rotation remains a critical management strategy. By rotating sorghum with non-host crops, farmers can significantly reduce the concentration of teliospores in the soil.

Planting resistant varieties is the most sustainable approach, as genetic resistance provides built-in protection against local strains of the pathogen.

Agronomic practices that ensure rapid germination and vigorous seedling growth, such as optimal soil temperature at planting, can help plants outpace the initial infection phase.

• Utilize high-quality, fungicide-treated certified seeds.
• Practice deep tillage to bury crop residues and reduce surface inoculum.
• Avoid planting in cold, wet soil conditions that favor pathogen development.