IntroductionThe root-knot nematodes (RKN), especiallyMeloidogynespp., are globally emerging harmful animals for many agricultural crops.MethodsTo explore microbial agents for biological control of these nematodes, the microbial communities of the rhizosphere soils and roots of sponge gourd (Luffa cylindrica) infected and non-infected byM. incognitanematodes, were investigated using culture-dependent and -independent methods.ResultsThirty-two culturable bacterial and eight fungal species, along with 10,561 bacterial and 2,427 fungal operational taxonomic units (OTUs), were identified. Nine culturable bacterial species, 955 bacterial and 701 fungal OTUs were shared in both four groups. More culturable bacterial and fungal isolates were detected from the uninfected soils and roots than from the infected soils and roots (except no fungi detected from the uninfected roots), and among all samples, nine bacterial species (Arthrobactersp.,Bacillussp.,Burkholderia ambifaria, Enterobacteriaceae sp.,Fictibacillus barbaricus,Microbacteriumsp., Micrococcaceae sp., Rhizobiaceae sp., andSerratiasp.) were shared, withArthrobactersp. andBacillussp. being dominant.Pseudomonas nitroreducenswas exclusively present in the infested soils, whileMammaliicoccus sciuri,Microbacterium azadirachtae, andPriestiasp., together withMucor irregularis,Penicilliumsp.,P. commune, andSordariomycetessp. were found only in the uninfected soils.Cupriavidus metallidurans,Gordoniasp.,Streptomyces viridobrunneus, andTerribacillussp. were only in the uninfected roots whileAspergillussp. only in infected roots. AfterM. incognitainfestation, 319 bacterial OTUs (such asChryseobacterium) and 171 fungal OTUs (such asSpizellomyces) were increased in rhizosphere soils, while 181 bacterial OTUs (such asPasteuria) and 166 fungal OTUs (such asExophiala) rose their abundance in plant roots. Meanwhile, much more decreased bacterial or fungal OTUs were identified from rhizosphere soils rather than from plant roots, exhibiting the protective effects of host plant on endophytes. Among the detected bacterial isolates,Streptomycessp. TR27 was discovered to exhibit nematocidal activity, andB. amyloliquefaciens,Bacillussp. P35, andM. azadirachtaeto show repellent potentials for the second stageM. incognitajuveniles, which can be used to develop RKN bio-control agents.DiscussionThese findings provided insights into the interactions among root-knot nematodes, host plants, and microorganisms, which will inspire explorations of novel nematicides.