Sorghum rust

Puccinia purpurea is a specialized fungal pathogen belonging to the kingdom Fungi, phylum Basidiomycota, and the order Pucciniales. It acts as an obligate parasite that specifically infects plants of the genus Sorghum. This pathogen is the causal agent of sorghum rust, a disease that can cause significant economic losses in sorghum-growing regions worldwide by affecting photosynthetic capacity.

The disease is characterized by the formation of small, purple to reddish-brown uredinia (pustules) on both sides of the leaves. These pustules often develop halos of chlorotic tissue. As the infection progresses, the pustules rupture the epidermis, releasing mass amounts of spores. In severe cases, extensive leaf desiccation occurs, which directly impacts the grain filling and vegetative biomass of the plant.

The life cycle of Puccinia purpurea involves the production of urediniospores, which are the primary means of dispersal. These spores are wind-borne and can travel long distances to infect susceptible hosts. In regions with mild winters, the fungus can survive as dormant mycelium or spores on volunteer sorghum plants or perennial hosts, serving as a continuous source of primary inoculum for new crops.

The development and spread of sorghum rust are heavily dependent on environmental conditions. High humidity, presence of surface moisture (like dew or light rain), and moderate temperatures (between 20°C and 25°C) are critical for spore germination and successful penetration into host tissues. Dense canopy cover within the field further exacerbates these conditions, promoting the rapid spread of the disease.

Effective management and control of Puccinia purpurea require an integrated pest management (IPM) approach. The most sustainable method is the deployment of resistant or tolerant sorghum cultivars. Additionally, sanitation practices, such as the destruction of crop residues and the control of volunteer plants, are vital to reducing initial inoculum levels. Fungicidal applications may be necessary in high-risk scenarios or during severe outbreaks.

• Use of disease-resistant hybrids.
• Crop rotation with non-host species.
• Timely removal of infected crop debris.
• Application of systemic fungicides when necessary.