Rhizopus microsporus

Rhizopus microsporus is a filamentous fungus belonging to the kingdom Fungi, phylum Zygomycota. It acts as a common soil saprotroph that can transition into a highly destructive phytopathogen under favorable environmental conditions. It is globally distributed and poses a significant threat to various agricultural and horticultural crops.

This pathogen is primarily known for causing soft rot, root rot, and post-harvest decay. It affects a wide range of hosts, including sunflowers, strawberries, tomatoes, sweet potatoes, and several grain crops. The infection leads to rapid tissue maceration, often resulting in complete crop loss if environmental conditions remain suitable for fungal growth.

The biology of Rhizopus microsporus is characterized by rapid mycelial expansion and massive spore production. It propagates via sporangiospores, which are easily disseminated by wind or physical contact. The fungus secretes potent cell-wall-degrading enzymes, such as pectinases, which collapse host cell structures and provide nutrients for the rapidly growing fungal colony.

Environmental factors play a decisive role in the disease development, with high humidity and temperatures between 25°C and 35°C being optimal. Moisture films on leaf surfaces or fruit skins are essential for spore germination. Wounds or insect bites on the plant surface create entry points, making the plant highly susceptible to systemic colonization by the fungus.

The impact of this pathogen is economically devastating due to the speed at which it destroys agricultural produce. Effective management requires an integrated approach to mitigate infection risks:

• Crop rotation to reduce fungal inoculum levels in the soil.
• Strict sanitation protocols for storage facilities and transportation equipment.
• Temperature and humidity management to inhibit fungal growth during post-harvest storage.
• Minimizing physical injuries to crops during harvesting and handling processes.
• Applying appropriate fungicidal treatments if environmental forecasts predict high risk of infection.