Rice rhizopus

Taxonomic position and pathogen nature: Rice rhizopus (Rhizopus oryzae) belongs to the kingdom Fungi, phylum Zygomycota, and the genus Rhizopus. It acts as both a common saprotroph and a destructive phytopathogen. It is globally distributed and is particularly noted for its ability to infect a wide array of plant tissues during the post-harvest stage.

Diseases and host plants: This fungus is the primary agent responsible for soft rot, fruit rot, and root rot. Among the most susceptible crops are rice, corn, strawberries, peaches, apples, and sweet potatoes. The pathogen usually gains entry into the plant tissues through wounds, bruises, or cracks that occur during handling, harvesting, or as a result of insect damage.

Biology and life cycle: The fungus reproduces primarily via asexual sporangiospores, which are produced in large quantities within sporangia. These spores are highly mobile and easily dispersed by air currents. Under unfavorable conditions, Rhizopus oryzae can produce thick-walled zygospores, which allow the fungus to persist in soil and organic debris for extended periods.

Developmental conditions and impact: The pathogen thrives in warm, humid conditions, with an optimal temperature range between +25°C and +35°C. Its impact is characterized by rapid tissue disintegration, often referred to as "soft rot." Within a few days, affected produce can become entirely covered in a gray, cottony mycelial mass, leading to total loss of market value and nutritional content.

• Implementing strict temperature control in storage facilities
• Minimizing physical damage during harvesting and transport
• Sanitizing storage units, crates, and harvesting equipment
• Removing and destroying infected plant debris
• Applying preventive fungicides to seeds and soil

Defense and control measures: Effective management relies on prevention and sanitation. Maintaining adequate ventilation and low relative humidity is crucial for stored crops. In the field, cultural practices such as proper crop rotation, avoiding over-fertilization with nitrogen, and using resistant cultivars can help reduce the incidence of Rhizopus oryzae infections.