Sclerospora graminicola

Sclerospora graminicola is an obligate biotrophic oomycete belonging to the kingdom Chromista. It is recognized primarily as the causal agent of "green ear" disease, also known as downy mildew, which severely affects pearl millet (Pennisetum glaucum) and several other grass species globally.

The pathogen causes systemic infection in host plants, resulting in striking symptoms such as chlorosis, stunted growth, and the characteristic transformation of floral parts into green, leafy, sterile structures. In severe cases, the entire panicle is deformed, completely preventing seed set and leading to total crop failure on the affected plants.

The life cycle of Sclerospora graminicola is highly adapted to the survival of the host. The fungus persists in the soil and on crop residues in the form of thick-walled oospores, which can remain dormant for several years. Upon the return of moisture and favorable temperatures, oospores germinate to infect emerging seedlings, with the mycelium subsequently invading the apical meristem to achieve systemic infection.

Environmental conditions play a critical role in disease epidemiology. Warm temperatures and high humidity, particularly during the germination phase, trigger the production of sporangia, which are disseminated by wind and rain splash. This facilitates rapid secondary cycles of infection within a single season, allowing the pathogen to spread efficiently across susceptible fields.

Management strategies focus on a multi-pronged approach to minimize inoculum pressure and protect plants.

• Using systemic fungicide seed treatments (e.g., metalaxyl-based) is the most effective way to prevent early systemic infection.
• Crop rotation of 3–4 years helps reduce soil-borne oospore populations.
• Selecting resistant or tolerant hybrids is a primary defensive strategy in regions with high disease incidence.
• Field sanitation, including the removal of infected plant debris, is vital for long-term disease suppression.