Direct antagonistic effect of entomopathogenic nematodes and their symbiotic bacteria on root-knot nematodes migration toward tomato roots

Abstract

Aims Negative interactions in the rhizosphere between entomopathogenic nematodes (EPNs) and plantparasitic nematodes, such as root-knot nematodes (RKNs), have been documented over the past two decades but the mechanisms and dynamics of such interactions remain largely elusive.Methods Here, we evaluated the effect of inoculation position of two EPN species, Steinernema feltiae and Heterorhabditis bacteriophora, as well as different facets of the EPN-bacterial symbiont complex on the migration of RKNs toward tomato roots, both in sand and in Pluronic gel conditions.Results When EPNs were placed between the position of the RKNs and the roots, the movement of RKNs toward the roots was inhibited. We observed this same pattern both in sand and in Pluronic F-127 (PF-127) gel and for two species of EPNs. We also observed that different components of the EPNs/bacterial symbiont complex (bacteria separate from the nematodes vs. the nematode-bacterium complex), and particularly the cell-free supernatant produced by the bacterial culture, displayed inhibitory effects on RKNs.Conclusions Therefore, the EPNs/bacterial complex, by slowing down the movement of RKNs toward the host plant roots, can function as an effective biocontrol strategy. By screening for the most repulsive strains of EPNs that are also effective against insect pests, such combined target suppression should alleviate EPNs application costs in integrated pest management practices.

Nurturing belowground life: the role of cover crops in shaping soil microbial communities in agroecosystems

“…It is therefore plausible that cover crops, especially good hosts for M. chitwoodi, could have had an effect on the group of predatory nematodes, but this was not measurable in the study. It is important to note that the predatory activity of nematodes such as Mononchoides is typically highest in the plant rhizosphere, where the nematode densities are higher (Jiang et al, 2017b;Li et al, 2023b), whereas the study in Chapter 4 focused on bulk soil samples at the termination of the cover crop growth.…”