Root cortex--the final frontier for the biocontrol of root-rot with fungal antagonists: a case study on a sterile red fungus.

Root cortices remain as the last frontier for the biocontrol agents to protect the vascular elements from the invader, where the virulent pathogen has breached the bulk soil, rhizosphere, and rhizoplane. Root cortices are commonly colonized by a variety of soilborne fungi. Many nonmycorrhizal biocontrol fungi that occupy the rhizosphere appear to extend their activity into the live cells of the cortex. It has been proposed that the occupation of the cortices by biocontrol fungi introduced on seed at sowing could extend their activity in time and space. The biology and ecology of such fungi with parasitic competency to colonize live cortical cells are discussed in relation to a case study involving a sterile cortical fungus.