Detection and diversity of nematodes in the rhizosphere and bulk soil of oilseed rapeand wheat grown in shortened rotations

Abstract: A long-term field experiment of OSR grown in a range of rotations with wheat wasused to determine whether shifts in nematode populations of the rhizosphere and bulk soil couldbe identified. DNA was extracted from the rhizosphere and the bulk soil, and nematodecommunities were profiled by Terminal Restriction Fragment Length Polymorphism (TRFLP)using nematode specific primers to the 18s ribosomal RNA gene. TRFs were identified byconstruction of a clone library. Nine different families of nematodes were detected in the clonelibrary from the continuously cropped OSR rhizosphere, including three families containingknown plant pathogens, including Pratylenchus neglectus (root lesion nematode), Coslenchusfranklinae, Bitylenchus dubius and Tylenchorhynchus dubius. There was a significant differencebetween the nematode communities in the rhizosphere of the different crops, but there was nodifference in the bulk soil. There was also a significant difference between the nematodecommunities of the rhizosphere soil and bulk soil, due mainly to an increase in the relativeabundance of plant pathogenic nematodes in the rhizosphere, in particular Pratylenchusneglectus. Further primers were designed to amplify the cyst nematodes within the generaHeterodera. The TRF corresponding to these pathogenic nematodes was not detected in this fieldtrial, but has been detected at high levels in another site within the UK.