Chickpea root rot

The primary symptom of the disease is the darkening and softening of the root system and the crown area of the stem. As the infection progresses, necrotic lesions form, which physically impede the transport of water and nutrients to the plant canopy.

Visually, the disease presents as premature wilting of the plants, typically starting from the lower leaves. The leaves gradually yellow and dry out, but they often remain attached to the stem for a significant duration, which is a key diagnostic feature.

Upon closer inspection of the crown area, one may observe a whitish or greyish mycelial mat. Eventually, the fungal structures known as pycnidia develop on the affected tissues, appearing as minute dark spots.

The progression of the disease leads to significant stunting and overall suppression of plant growth. Plants infected at early stages often succumb before reaching the flowering phase, leading to thin stands and bare patches in the field.

The root system of infected chickpeas appears poorly developed, showing clear signs of rot on fine lateral roots. Eventually, the taproot may undergo total degradation, leaving the plant loose and unstable in the soil.

The pathogen responsible for the disease is the microscopic fungus Phacidiopycnis padwickii, classified within the group of anamorphic fungi. This organism is capable of surviving in soil and on infected crop residues for extended periods, awaiting favorable conditions for infestation.

The fungus has a broad host range, notably affecting crops such as chickpeas, sweet potatoes, and certain varieties of rice. This polyphagous nature makes it particularly dangerous in diverse cropping systems.

Reproduction of the pathogen occurs via pycnidia that develop within host tissues. The released conidia are easily dispersed by rain splashes, irrigation water, soil-borne pests, and even contaminated agricultural machinery.

The biology of the fungus allows it to endure adverse environmental conditions through the formation of mycelium and chlamydospores. The high adaptability of the pathogen facilitates its survival across varied pedoclimatic zones.

Primary infection typically occurs through mechanical injuries to the root system sustained during planting or field operations. Natural openings in root hairs also serve as entry points for the fungal infection.

Root rot development is favored by high soil moisture and air temperatures ranging from 20 to 25 degrees Celsius. Waterlogging, resulting from poor soil aeration or excessive precipitation, significantly accelerates the pathogen's spread.

Plants weakened by mineral nutrient deficiencies or environmental stress factors exhibit increased susceptibility to the fungal invasion. Failure to adhere to optimal planting dates often contributes to the severity of the disease.

Soils with a neutral to slightly acidic pH often provide a conducive environment for the build-up of the pathogen in the rhizosphere. Soil compaction and poor structure lead to moisture retention, which stimulates the fungal mycelium growth.

Significant accumulation of fungal spores is observed under monoculture conditions when chickpeas are grown on the same field more frequently than once every 3–4 years. Unincorporated crop debris serves as the primary reservoir for the fungus.

Temperature fluctuations and cold spells during the seed germination phase reduce the seedling's natural defense mechanisms, allowing the pathogen to penetrate the young tissues more effectively.

The economic impact of root rot lies in the significant reduction of plant density, which directly impacts the potential yield. High mortality rates among seedlings necessitate reseeding operations, resulting in substantial financial loss.

Infected plants display poorly developed generative organs, leading to the formation of shriveled seeds or total pod failure. This decreases both the volume of the harvest and the overall quality of the grain.

The disease disrupts photosynthesis and metabolic processes, preventing the plant from achieving its genetic yield potential. Furthermore, the infection promotes premature senescence of the chickpea tissues.

Indirect losses are associated with the costs of additional disease management interventions and soil sanitation efforts. Additionally, infected fields become a source of inoculum for neighboring agricultural areas.

In cases of severe infestation, yield losses can range from 15 to 40 percent, making the effective control of Phacidiopycnis padwickii a critical factor for the profitability of chickpea production.

The fundamental management strategy involves strict adherence to crop rotation, ensuring that chickpeas are not planted in the same field more than once every four years. Rotating with non-host crops is essential for breaking the disease cycle.

Seed treatment with certified fungicides prior to sowing is a mandatory step in the management program. This treatment destroys spores present on the seed surface and provides early-season protection to the emerging seedlings.

Deep plowing with proper incorporation of crop residues significantly reduces the soil-borne inoculum. Agronomic practices aimed at improving soil aeration and drainage are crucial for minimizing the risk of rot development.

The use of resistant chickpea varieties remains the most effective and environmentally sustainable control method. Breeding for immunity or resistance to Phacidiopycnis padwickii is a key focus for research programs worldwide.

During the growing season, regular monitoring of the field is recommended to identify early signs of wilting and to quarantine infection foci. Balanced fertilization with potassium and phosphorus helps boost the plant's overall resilience to fungal infections.