Sorghum anthracnose

Colletotrichum sublineola is a devastating fungal phytopathogen belonging to the kingdom Fungi, specifically known as the causative agent of sorghum anthracnose. This fungus is highly host-specific, primarily targeting grain and forage sorghum. It is considered one of the most economically significant constraints to sorghum production worldwide, capable of infecting plants at various growth stages, from seedlings to mature crops.

The symptoms of the disease appear as necrotic lesions on leaves, sheaths, and peduncles. These lesions often display a range of colors and shapes, frequently surrounded by chlorotic or dark margins. Under humid conditions, the pathogen produces characteristic black acervuli, which are fruiting bodies containing abundant masses of conidia. Stem infections often lead to internal rot (red rot), significantly weakening the stalk and causing lodging.

The biology of Colletotrichum sublineola involves survival between cropping seasons on infected crop residues and contaminated seeds. Primary inoculum is disseminated by wind and rain splash onto healthy plant tissue. The infection process is highly dependent on environmental conditions, with high humidity and leaf wetness being essential. Optimal temperatures for the development and rapid spread of the pathogen range from 25°C to 30°C.

The impact of this disease on agricultural systems is profound. Infected plants experience reduced photosynthetic capacity, premature senescence, and impaired grain filling. In severe cases, the grain becomes shriveled, and the head filling is reduced or aborted entirely. Yield losses in susceptible commercial hybrids can exceed 50%, particularly in regions with high rainfall during the flowering and grain-filling periods.

Integrated disease management (IDM) is crucial to minimize the impact of the pathogen:

• Selection and planting of host-plant resistant hybrids.
• Crop rotation with non-host crops to reduce soil-borne inoculum.
• Sanitation practices, including the removal or deep incorporation of crop debris.
• Use of fungicide-treated seeds to minimize initial seedling infection.
• Foliar fungicide applications during the early stages of disease appearance when environmental conditions favor spread.