DIFFERENTIATION AND DEVELOPMENT OF THE SPECIALISED INFECTION STRUCTURES FORMED BY BIOTROPHIC FUNGAL· PLANT PATHOGENS

Biotrophic fungal plant pathogens, including the powdery mildew, downy mildew and rust fungi, allow the infected plant cells and tissues to remain alive and active for extensive periods in order to obtain nutrients. They all develop specialised infection structures called haustoria, within plant cells, that form an interface between the fungal parasite and host plant [1]. The key interface is the extrahaustorial membrane (ehm), which is an invagination of the host plasma membrane, and this is likely to be involved in the transport of nutrients to the fungus and recognition/signalling between the plant and the fungus [1]. Organisms such as Colletotrichum lindemuthianum also have a biotrophic phase of infection involving a specialised infection structure, the intracellular hypha (IH). However, after several days, biotrophy breaks down, leading to a necrotrophic phase of development in the plant, and such organisms are termed hemibiotrophs or facultative biotrophs [2].