3. Types of hyperparasitic relationships

One of the ways fungal hyperparasites are defined is based on the state (living or dead) of the primary parasite (Barnett and Binder, 1973). Fungi that exploit living host tissue or cytoplasm are considered biotrophs, whereas necrotrophs kill host cells and then utilize host biomass (Benjamin et al., 2004; Jeffries and Young, 1994). Biotrophic hyperparasites typically have a narrower range of hosts and develop specialized structures to interact with their hosts (Jeffries, 1985, 1995). Examples of biotrophic hyperparasites and their parasitic hosts are given in Table 1. Many of these biotrophic hyperparasites form haustoria or specialized hyphal branches involved in absorption of food from host mycelia or sclerotia (Kirk et al., 2008). Necrotrophs frequently use antifungal compounds in so-called hyphal interference (when the host is a fungus) or destroy the cell wall and membranes of host tissue to gain access to cellular contents, or use a combination of these strategies (Jeffries and Young, 1994).