Globodera spp. are under strict quarantine in many countries. Suppressiveness to cyst nematodes can evolve under monoculture of susceptible hosts. Females developing in potato monoculture soil infested with G. pallida populations Chavornay or Delmsen were examined for inherent microbial communities. In the greenhouse, nonheated and heat-treated (134°C for 10 min) portions of this soil were placed in root observation chambers, planted with Solanum tuberosum 'Selma', and inoculated with G. pallida Pa3 Chavornay. At harvest in Delmsen soil, cysts had fewer eggs in nonheated than heat-treated soil. In denaturing gradient gel electrophoresis analysis, bacterial and fungal fingerprints were characterized by a high variability between replicates; nonheated soils displayed more dominant bands than heated soils, indicating more bacterial and fungal populations. In amplicon pyrosequencing, females from nonheated portions frequently contained internal transcribed spacer sequences of the fungus Malassezia. Specific for the Chavornay and Delmsen population, ribosomal sequences of the bacteria Burkolderia and Ralstonia were abundant on eggs. In this first report of microbial communities in G. pallida raised in potato monoculture, candidate microorganisms perhaps associated with the health status of the eggs of G. pallida were identified. If pathologies on cyst nematodes can be ascertained, these organisms could improve the sustainability of production systems.

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SummaryAnaerobic digestate is a byproduct of anaerobic digestion of organic materials for biogas production. Land application of digestates may provide plant nutrition and suppression of plant-parasitic nematodes. The characteristics of digestates may vary by organic substrates and digestion conditions. To measure nematode-suppressive potential, the rigour and simplicity of a radish bioassay with Heterodera schachtii was expanded. In a three-factor factorial design, three incubation environments, two growth containers and two nematode life stages as inoculum were tested. Containers with 50 g of dry sandy loam soil were inoculated with 500 second-stage juveniles (J2) of H. schachtii or with cysts with equivalent hatchable J2. One seed of radish Raphanus sativus ‘Cherry Belle’ was planted into each container, and 1 ml of drench treatment was applied. After 64 degree days (4-5 days), roots were washed and stained with acid fuchsin for nematode counting. In three experiments, food waste digestate permeate suppressed nematode root penetration in the growth chamber, glasshouse and laboratory, in cups and tubes, and following inoculation with cysts and J2. However, root penetration by J2 was more greatly reduced after cyst inoculation than after J2 inoculation. Investigations in preserving nematode cysts showed that J2 within cysts remained viable after incubation in sandy loam soil at 23°C in sealed tubes in the laboratory for 35 days. Results of the radish assay predicted nematode-suppressive potential against Pratylenchus vulnus on peach rootstock ‘Nemaguard’ in a glasshouse experiment. In summary, a straightforward rapid bioassay for measuring nematode suppressiveness of organic liquids was developed for routine use.

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