By infecting nematodes the nematophagous fungi have the ability to thrive in a sheltered environment protected from other soil microorganisms. There are reports that nematophagous fungi form antibiotic compounds upon infection of nematodes (Barron 1977). The vermiform nematodes are actively moving in soil and are chemically attracted to the nematode-trapping and endoparasitic fungi (Jansson and Nordbring-Hertz 1988). After contact with the infective structure (trapping organ or spore) the nematode becomes attached, which eventually leads to penetration of the host (Tunlid et al. 1992). Since the nematodes move vigorously and also have high internal hydrostatic pressure the production of an efficient adhesive is vital for successful infection, both as a holdfast and for sealing the penetration area. The nonmotile nematode eggs may be infected by egg-parasitic fungi, the hyphae of which actively grow towards the egg. Upon contact the fungus forms an appressorium that adhere to the eggshell. This stage is followed by penetration of the egg shell and digestion of the contents of the egg (premature or mature juveniles). Infected and dead nematodes may constitute a means for the nematophagous fungi to survive in soil during harsh environmental conditions.
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