Nematodes affect root architecture and the quantity and quality of root exudation and have significant effects on the rhizosphere microbial community. Soils suppressive to nematodes in agro-ecosystems and in natural habitats are studied to understand the dynamics of the interactions between microbial natural enemies and plant parasitic nematodes. The genome of the bacterial parasite of nematodes, Pasteuria penetrans is being sequenced in collaboration with NCSU. Genes associated with host recognition and pathogenicity will be targets for further research.

Pochonia chlamydosporia is an important parasite of the potato cyst nematode in the UK and its significance in the population regulation of this major UK pest is being investigated with uplift funding. Pochonia chlamydosporia is a facultative parasite and its abundance in soil is not necessarily related to its impact as a biological control agent. The parasitic activity of the fungus is much affected by its nutritional status and it is hypothesised that nematode females alter root exudation which triggers the fungus to switch from its saprophytic phase in the rhizosphere to its parasitic phase within nematode egg masses. The influence of nutrition on the expression of parasitism genes in the fungus is studied with especial reference to the serine proteinase VCP1. The gene for this enzyme has been cloned and sequenced and is involved in the early stages of nematode egg infection. Uplift funding will be used to determine if this and other enzymes may be used as indicators of the switch in trophic states of the fungus. Understanding the regulation of its trophic phases will enable its predictable manipulation in the field.