Composition and function of bacterial communities associated with the northern root-knot nematode (Meloidogyne hapla) populations showing parasitic variability

The northern root knot nematode Meloidogyne hapla is an important crop pest of temperate agriculture responsible for several losses. In addition, M. hapla populations with no known detectable genetic or morphological differences have parasitic variability (PV) which is indicated by their reproductive potential on host plants. Particularly, M. hapla populations from mineral and muck soils with varying degrees of soil health conditions have been found to have PV. However, it is not known what microbial relationships or the lack of, are associated with M. hapla populations PV. Using M. hapla populations isolated from mineral and muck soil fields with disturbed and degraded soil health conditions, and greenhouse cultures showing PV, the populations were studied for the presence and/or absence of specific bacterial composition and potential functional groups. The 16S ribosomal region of field and greenhouse isolated M. hapla populations were sequenced to characterize the bacterial communities. The results showed 65 genera in the field and 61 genera in the greenhouse had a variable composition with 14 potential functional groups and unknown or other groups. Population 13 with the highest PV was associated with the unique absence of Mesorhizobium and Ohtaekwangia in the field and Devosia, Kibdelosporangium, Mycobacterium and Steroidobacter in the greenhouse. On the other hand, the medium PV of Population 8 was uniquely associated with the presence of Brevundimonas, Candidatus Udaeobacter, Hyphomicrobium, Mucilaginibacter, Nocardioides, Roseiarcus and Solirubrobacter in the field and Hyphomicrobium in the greenhouse. The low reproductive potential of M. hapla was found to be associated with several bacteria. The findings of this study lay the foundation in establishing potential cause and effect relationships associated with M. hapla PV.