Prospects and limitations for mycorrhizas in biocontrol of root pathogens

More than 80 disease biocontrol products are on the market worldwide, but none of these contain mycor rhizal fungi. This is despite ample evidence that both arbuscular mycorrhizal fungi and ectomycorrhizal fungi can control a number of plant diseases. A procedure for successful development of disease biocontrol agents in general is used as a background to examine the potential for achieving commercial mycorrhizal biocontrol agents. This includes (i) selection and screening; (ii) characterization involving identification, studies of modes of action and ecophysiology, as well as inoculum production, formulation, application and shelf life; (iii) registration. The last stage is problematic for mycorrhizal fungi, as currently they can be sold as plant growth promoters without any form of costly registration, even though in some instances they may actually function to some extent through biocontrol activity. The significance of this approach is discussed, and some possible ways of enhancing biocontrol by mycorrhizas are considered.