What Is The Rhizoctonia Solani Complex?

The Rhizoctonia solani complex represents an economically important group of soilborne plant pathogens that can cause infection on many plant species throughout the world (Whisson et al 1995; Sneh et al. 1996 ). The pathogens are mainly perpetuated through infected propagation materials, originating from infected plants (Maas, 1984). Once the plants get infection, sclerotia of the pathogen are surrounded by sloughed plant cells, thus improving their survival rate in soil (Maas, 1984). It can persist in soil for longer duration in form of sclerotia thus soil inoculum is playing an important source for infection. Subsequently, these propagules are dispersed and infect roots of the same and adjacent plants because it is having wide host range
solani. For some R. solani AG, wind-dispersed basidiospores may serve as the primary inocula for inciting foliar diseases of various cultivated plant species under favorable environmental conditions (Naito 1996). In general, however, basidiospores are not the primary inocula responsible for infections, and most Rhizoctonia diseases result from initial infection by propagules (sclerotia or mycelia, often in association with plant debris) that are able to survive for many years in soil. Disease resulting from infection via sclerotia or mycelia often appear as clusters (aggregates) of infected plants within a field, whereas disease resulting from basidiospore infection often appears as a random, uniform pattern of infected plants throughout the field (Naito 1996). Although basidiospores may not be of epidemiological significance for most Rhizoctonia root and seedling diseases during a growing season, they may have important ecological and population consequences. Innate mechanisms of basidiospore dispersal (i.e., repetitive spore germination and forcible discharge at night), as well as the immigration and vegetative spread of sclerotia and mycelium associated with agricultural practices, are well documented and would contribute significantly to the temporal and spatial distribution of R. solani genotypes in natural populations. Meiotic reproduction may provide a mechanism for generating genetic diversity in a population even if the primary mode of reproduction is asexual (McDonald et al. 1995). Molecular Markers in Rhizoctonia—The Need for Population Genetics Future advances in understanding Rhizoctonia population biology almost certainly will rely heavily on the application of genetic markers to characterize the genotypic structure of populations. A variety of molecular markers have been applied to the study of