Binucleate Rhizoctonia

Binucleate Rhizoctonia represents a group of fungi within the genus Rhizoctonia, distinguished primarily by having two nuclei in their vegetative hyphal cells. Taxonomically, these fungi are often linked to the teleomorph stage Ceratobasidium. Unlike the multinucleate Rhizoctonia solani, binucleate species exhibit distinct genetic and physiological characteristics that vary depending on their specific anastomosis group.

These pathogens are responsible for various plant diseases, primarily affecting the root system and the lower stem. Symptoms include damping-off of seedlings, root rot, and stunting. Crops such as strawberries, potatoes, beans, and various ornamental plants are highly susceptible to infection. The presence of these fungi often leads to uneven crop emergence and reduced overall stand density in the field.

The biology of these fungi is centered on their ability to survive in the soil as sclerotia or as mycelium on plant debris. They act as facultative parasites, meaning they can thrive on dead organic matter but rapidly infect living tissue when environmental conditions are conducive. The pathogen spreads through infested soil particles, irrigation water, and infected plant material, making sanitation a critical component of disease management.

Development is most favorable in moist and moderately warm soil conditions. High humidity levels, combined with compaction or poor soil aeration, create an environment where the fungus can rapidly colonize roots. Because they are ubiquitous in many soils, their impact often intensifies under monoculture systems or when crops are subjected to abiotic stress factors like drought or cold.

Managing binucleate Rhizoctonia requires a proactive strategy due to its soil-borne nature. Since it is difficult to eradicate completely, the focus shifts towards prevention and suppression:

• Utilizing disease-free planting material to avoid introducing the pathogen.
• Improving soil drainage to minimize conditions favorable for fungal growth.
• Employing cover crops to break the disease cycle and improve soil health.
• Applying biological control agents, such as specific strains of Trichoderma, to compete with the pathogen in the rhizosphere.