Downy mildew of chickpea

Taxonomic position and pathogen nature: Peronospora ciceris is classified within the kingdom Chromista, phylum Oomycota, and family Peronosporaceae. Often misidentified as a fungus, it is actually an oomycete, an obligate parasite that depends entirely on living chickpea tissues for its nutritional needs and reproductive cycle.

Diseases and host plants: This pathogen is the causal agent of downy mildew in chickpea (Cicer arietinum). It is a highly host-specific disease that poses a threat to chickpea production in regions experiencing cool and humid weather conditions during the crop's growth stages.

Biology and life cycle: The pathogen survives the off-season as thick-walled oospores present in soil or on crop debris. Under favorable conditions, these spores release motile zoospores that infect the young seedlings. Throughout the season, the pathogen produces conidia, which act as secondary inoculum, spreading the disease via wind and splashing water to healthy neighboring plants.

Development conditions and impact: Development is favored by temperatures ranging from 15°C to 20°C and high humidity (above 80%). The disease symptoms appear as chlorotic spots on leaves, eventually leading to necrosis and premature senescence. This loss of photosynthetic capacity significantly reduces grain filling and overall yield, often leading to severe economic losses in sensitive varieties.

Protection and control measures: Effective management of downy mildew requires an integrated approach:

• Selection of resistant or tolerant chickpea cultivars for planting.
• Practicing strict crop rotation with non-host crops to reduce soil-borne inoculum levels.
• Proper field sanitation, including the deep plowing of infested crop residues after harvest.
• Timely application of systemic and contact fungicides (e.g., metalaxyl or copper-based compounds) based on weather monitoring and early detection.