Ascochyta blight of Chickpeas

Ascochyta blight is perhaps the most frequent and damaging disease of chickpea worldwide. It is caused by Ascochyta rabiei, a fungus that selectively attacks chickpea. Then persists in the crop’s residues, seed, and volunteer plants. Infections may arise from seedborne inoculum or from windborne spores (ascospores). Infections usually begin low in the crop canopy during periods of cool, wet weather. All parts of the plant above the soil line are subject to attack and may develop elongated, sunken, dark lesions. Lesions often girdle stems, weaken and break branches and petioles (leaf stems), and kill all plant parts above the lesion. Within the lesions, the fungus produces fruiting bodies (pycnidia) that become visible as tiny, black, raised spots, often arranged in concentric rings.
In the field, Ascochyta blight first appears on small groups or patches of plants. The initial distribution of blight symptoms may reflect how the primary inoculum was spread, which can occur in three ways: 1) in or on seed, 2) by wind, or 3) from site infested residues or volunteer plants. Initial infection sites in a field that are uniformily distributed tend to indicate the infection spread from seedborne inoculum. Less uniform blight distribution may indicate inoclulm spread by wind or residue. Because moisture is essential for infection and blight development, infection sites may be localized in lowlands or under sprinkler irrigation.
Under cool moist conditions, the patches of diseased plants in the field may rapidly increase in size, and lesions may develop higher in the crop canopy on leaves and pods. Pod infection leads ultimately to seed infection. Such seed contamination is not always visible nor is the fungus in or on the surface of seed easy to detect in the laboratory. Only heavily infected seeds will bear visible blight symptoms, which include small size wrinkles, lesions, and/or dark discoloration.