Penicillium stoloniferum

The fungus is characterized by its complex, brush-like conidiophores that produce large amounts of asexual spores called conidia. These spores are highly resistant to environmental stress and are easily dispersed by air currents, water splashes, and insects, facilitating rapid colonization.

It possesses a robust enzymatic system capable of breaking down complex plant tissues, including cellulose and pectin. This ability makes it a major concern in post-harvest biology, as it easily attacks compromised plant materials.

In the field or in storage, the fungus develops a branched, septate mycelium that penetrates host tissue. As it grows, it secretes metabolites and enzymes that soften the tissue, causing it to collapse and facilitating the expansion of the fungal colony.

Its biological cycle is highly dependent on environmental variables. The fungus thrives in temperatures between +20 °C and +25 °C, provided there is adequate moisture or high relative humidity to sustain its metabolic activity and sporulation.

This pathogen causes significant economic losses through seed decay and post-harvest rot. It is particularly damaging to stored crops such as onions, potatoes, carrots, and various fruits, where it can cause widespread rot during long-term storage.

In seeds, the fungus infects the embryo and endosperm, leading to a drastic reduction in seed vigor and germination rates. If infected seeds are sown, the resulting seedlings often suffer from poor emergence or post-emergence damping-off.

Crop damage is often initiated through physical wounds created during mechanical harvesting or transportation. Once the surface barrier is breached, the pathogen enters the tissue and begins to decompose it rapidly.

Beyond physical damage, P. stoloniferum is known to produce various mycotoxins. These toxic substances can accumulate in the contaminated crop, making the produce unsafe for animal feed or human consumption.

In greenhouse settings, it frequently attacks seedlings, causing root rot that leads to significant plant loss. The combination of high plant density and controlled humidity makes these environments ideal for the spread of the pathogen.

The activity of P. stoloniferum is most prominent during the post-harvest period and in storage facilities. However, it can affect crops at any time of the year if the environmental conditions are suitable for fungal development.

In the field, the fungus remains active during the late stages of crop development, especially during seasons with excessive rainfall. These conditions promote the buildup of inoculum on leaves, stems, and soil.

During storage, the pathogen creates a persistent threat throughout the winter months. Poor ventilation in storage warehouses creates microclimates with stagnant, humid air, which serves as a catalyst for outbreaks of fungal rots.

Springtime activities, such as planting, pose another high-risk window. If seeds are sown into cold, wet, and poorly drained soil, the fungus will colonize the seeds faster than they can germinate, leading to stand loss.

During the summer months, the fungus serves as a decomposer of organic waste. This ensures a consistent reservoir of spores, which are then ready to infect the new crop as soon as harvest begins.

The most recognizable sign of P. stoloniferum infection is the formation of a fuzzy, dusty mold layer on the surface of the infected tissue. This mold typically appears white initially, maturing into a distinct blue-green or gray-green color.

Infected plant tissues lose their firmness and become soft and watery. In advanced stages, the internal tissue may turn brown or black, and the entire organ may lose its integrity, becoming covered in a thick layer of fungal spores.

Seeds infected by this pathogen often show discoloration and a dull appearance. A noticeable musty or earthy smell is also a common indicator of significant fungal growth within stored batches of grain or produce.

Microscopic examination of the affected areas reveals the presence of typical Penicillium-type conidiophores. Seedlings affected by this fungus exhibit brownish, necrotic lesions on the roots and the base of the stem.

• Blue-green dusty sporulation on the surface.
• Tissue softening, maceration, and loss of firmness.
• Musty or earthy odor in storage areas.
• Reduced germination percentage and poor seed vigor.
• Dark brown necrosis on plant roots and stems.

Management starts with rigorous agricultural practices. Deep plowing of crop residues is essential to bury the fungal inoculum and reduce its presence in the topsoil before the next planting cycle.

Ensuring proper drying of seeds and harvested produce is the most effective way to prevent P. stoloniferum. Maintaining moisture content at levels below the threshold for fungal growth is critical for long-term safety.

In storage warehouses, strict control of temperature and ventilation is mandatory. Preventing humidity spikes and avoiding the accumulation of condensation on stored goods limits the opportunities for the fungus to spread.

Chemical control involving seed treatment with systemic fungicides can protect crops during the vulnerable germination stage. These treatments provide a necessary shield against soil-borne spores.

Regular sanitation of storage areas and the removal of infected, decaying fruits from batches are key to preventing the spread of the pathogen to healthy produce, ensuring quality maintenance until the end of the storage period.