Phoma rot

Phoma exigua is a fungal plant pathogen belonging to the kingdom Fungi, genus Phoma, and species Phoma exigua. This organism acts as a destructive agent causing various types of rot, most notably in potatoes, legumes, and oilseed crops, significantly reducing agricultural yields globally.

The disease symptoms typically appear as necrotic lesions on stems, leaves, and tubers. In potatoes, the pathogen is widely known as the cause of gangrene, manifesting as dark, sunken lesions on the skin of stored tubers. These lesions often expand, leading to the internal breakdown of tissues into dry, crumbly, or cavity-filled rots.

The life cycle involves the production of pycnidia, which serve as fruiting bodies containing conidia. These spores are disseminated via wind, rain splashes, and farm machinery. The fungus persists in the soil on organic debris, in infected seeds, and within tubers, serving as a primary source of inoculum for subsequent growing seasons.

Environmental conditions such as cool to moderate temperatures (15–22°C) combined with high humidity are optimal for the growth and spread of Phoma exigua. Mechanical damage to plant tissues, often caused by agricultural operations or insect feeding, provides entry points for the fungus, exacerbating the spread of infection during wet weather.

Effective management requires an integrated pest management (IPM) approach. Key practices include the use of certified disease-free planting material, implementation of long-term crop rotation, and the prompt removal and destruction of crop residues. During storage, maintaining adequate ventilation and temperature control is crucial to prevent the progression of tuber rot.