Characterizing microbial communities associated with northern root-knot nematode () occurrence and soil health.

The northern root-knot nematode () causes extensive damage to agricultural crops globally. In addition, populations with no known genetic or morphological differences exhibit parasitic variability (PV) or reproductive potential based on soil type. However, why populations from mineral soil with degraded soil health conditions have a higher PV than populations from muck soil is unknown. To improve our understanding of soil bio-physicochemical conditions in the environment where populations exhibited PV, this study characterized the soil microbial community and core- and indicator-species structure associated with occurrence and soil health conditions in 15 Michigan mineral and muck vegetable production fields. Bacterial and fungal communities in soils from where nematodes were isolated were characterized with high throughput sequencing of 16S and internal transcribed spacer (ITS) rDNA. Our results showed that -infested, as well as disturbed and degraded muck fields, had lower bacterial diversity (observed richness and Shannon) compared to corresponding mineral soil fields or non-infested mineral fields. Bacterial and fungal community abundance varied by soil group, soil health conditions, and/or occurrence. A core microbial community was found to consist of 39 bacterial and 44 fungal sub-operational taxonomic units (OTUs) across all fields. In addition, 25 bacteria were resolved as indicator OTUs associated with presence or absence, and 1,065 bacteria as indicator OTUs associated with soil health conditions. Out of the 1,065 bacterial OTUs, 73.9% indicated stable soil health, 8.4% disturbed, and 0.4% degraded condition; no indicators were common to the three categories. Collectively, these results provide a foundation for an in-depth understanding of the environment where exists and conditions associated with parasitic variability.