Increase in C-14-carbon translocation to the soil microbial biomass when five species of plant-parasitic nematodes infect roots of white clover

Clonal white clover growing in pots was inoculated with Heterodera trifolii , Meloidogyne hapla, Meloidogyne trifoliophila, Pratylenchus sp., or Xiphin ema diversicaudatum. pulse-labelled with C-14 and after 15 days the distrib ution of C-14 in compartments of the roil: plant: nematode system determine d. Nematode inoculation had no effect on shoot, root and soil microbial bio masses, but the nematode treatments significantly affected the distribution of C-14 in these compartments. The greatest translocation of C-14 to the s oil was in pots with X. diversicaudatum, M. hapla or M. trifoliophila. The percentage of C-14 in the microbial biomass varied significantly, being hig hest with X. diversicaudatum and Pratylenchus sp., and lowest in control po ts. Nematodes of all species from the soil consistently had lower specific activity than those from roots. It has now been demonstrated for a range of nematodes and soils that nematode infection increases translocation of pho tosynthate to soil microbial biomass. As the soil microbial biomass plays a critical role in the availability of plant nutrients it appears that low i nfections of plant-parasitic nematodes may lead to greater availability of plant nutrients.