Ascochyta blight of chickpea

Didymella rabiei (anamorph Ascochyta rabiei) is a pathogenic ascomycete fungus that causes Ascochyta blight in chickpea (Cicer arietinum). Classified within the Didymellaceae family, this fungus is a highly specialized parasite. It is recognized as the most destructive disease affecting chickpeas worldwide, particularly in regions with cool and temperate climates where moisture levels are high during the growing season.

The pathogen attacks all aerial parts of the plant, manifesting as necrotic spots with a dark border. In the center of these lesions, small black fruiting bodies known as pycnidia develop, containing spores that facilitate the spread of the disease. In cases of severe infection, stems can break, leading to total lodging of the crop. Pods also become infected, resulting in shriveled or discolored seeds that carry the fungus internally.

The life cycle of Didymella rabiei involves both sexual and asexual stages. The pathogen survives the off-season on infected crop residues in the field and within infected seeds. Primary infection occurs via airborne ascospores produced in perithecia, while secondary cycles of the disease are driven by conidia splash-dispersed by rain. High humidity, frequent rainfall, and moderate temperatures are the key environmental triggers for disease progression.

The economic impact of this pathogen is severe, capable of reducing grain yield by 50% to 100% in susceptible cultivars. Beyond yield loss, the disease significantly degrades seed quality, making the grain unfit for both human consumption and export due to poor appearance and potential toxicity from fungal metabolites. The cost of managing this pathogen often dictates the profitability of chickpea cultivation in affected areas.

Effective management strategies against Didymella rabiei include:

• Utilization of disease-resistant or tolerant chickpea cultivars.
• Planting only high-quality, disease-free certified seeds.
• Implementing a rigorous crop rotation, leaving a gap of 3–4 years between chickpea crops.
• Deep burial of crop stubble to accelerate the decomposition of fungal inoculum.
• Timely prophylactic and curative application of registered foliar fungicides during periods of high disease risk.