Nematicidal Metabolites From Higher Fungi

Abstract

The adverse effects on human health and well being and the high economic losses inflicted by pathogenic nematodes are important stimulants for the search of new, safe and effective nematicides and anthelminthics. The pool of natural products is an important source for such compounds, and several of the most potent nematicides used today originate from streptomycetes. Higher fungi have an extensive secondary metabolism at their disposal, and obviously some benefit from the capability to kill nematodes. Surprisingly little is known about the production of nematicidal metabolites by fungi. Examples of compounds isolated from ascomycetes are the cochlioquinones and the mycorrhizins, which are strongly active against the saprophytic Caenorhabditis elegans but not towards the economically important plant pathogen Meloidogyne incognita. From basidiomycetes, the cyclic dodecapeptide omphalotin was obtained which seems to be highly selective for M. incognita. Compounds with good activity against a abomasum nematode in vivo are the macrodiolides clonostachydiol and helminidiol. When screening for nematicidal activity, it is important to use the proper test system as the sensitivity of different nematodes may vary considerably. Consequently, the search for agents active against M. incognita may be futile, if saprophytic nematodes are used as test organisms. The importance to develop relevant screening systems that are easy to use and have an acceptable capacity is therefore emphasized.