Rhizoctonia

Rhizoctonia is a genus of soil-borne fungi that includes numerous species capable of causing disease in a wide range of plants, as well as saprotrophic or endophytic lifestyles. The most important member is Rhizoctonia solani, a ubiquitous pathogen associated with damping-off of seedlings, root rot, stem cankers, and sheath blight in crops such as potatoes, cereals, vegetables, and ornamentals. The genus is characterized by filamentous hyphae and, in some species, the production of sclerotia that can persist in soil.

Rhizoctonia species reproduce asexually by multinucleate hyphae and can form sclerotia that survive in soil; some isolates also form a teleomorphic stage in the genus Thanatephorus. Classification often relies on anastomosis groups (AGs), which cluster isolates by hyphal fusion compatibility and correlate with host range and aggressiveness rather than strict species boundaries.

Pathogenic activity is favored by warm, moist soils and organic matter-rich environments. Symptoms depend on the host and disease form but commonly include crown or root lesions, seedling damping-off, stunted growth, and reduced yield. The fungus can persist in plant debris and soil, enabling recurring infections; spread occurs via contaminated soil, water, equipment, seed, and transplants. Rhizoctonia infections can affect a broad spectrum of crops and ornamentals, contributing to significant agricultural losses in many regions.

Management relies on integrated practices: sanitation, crop rotation away from susceptible crops, resistant cultivars where available, and proper irrigation to avoid excess moisture. Seed treatments and soil fungicides may be used in some crops, while biological control agents such as Trichoderma spp. have shown suppression of Rhizoctonia in certain cases. The genus remains a major constraint in commercial horticulture and agriculture worldwide.