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

Authors: LI, JINJING - Nankai University; LI, YANG - Nankai University; WEI, XIANQIN - Nankai University; CUI, YONGHE - Sichuan Academy Of Agricultural Science; GU, XINHU - Sichuan Academy Of Agricultural Science; LI, XINGYUE - Sichuan Academy Of Agricultural Science; YOSHIGA, TOYOSHI - Saga University; ABD-ELGAWAD, MAHFOUZ - National Research Centre; Shapiro Ilan, David; RUAN, WEIBIN - Nankai University; RASMANN, SERGIO - University Of Neuchatel

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2022
Publication Date: 12/31/2022
Citation: Li, J., Li, Y., Wei, X., Cui, Y., Gu, X., Li, X., Yoshiga, T., Abd-Elgawad, M., Shapiro Ilan, D.I., Ruan, W., Rasmann, S. 2022. Direct antagonistic effect of entomopathogenic nematodes and their symbiotic bacteria on root-knot nematodes migration toward tomato roots. Plant and Soil. Vol 484:1-15. https://doi.org/10.1007/s11104-022-05808-4.
DOI: https://doi.org/10.1007/s11104-022-05808-4

Interpretive Summary: Nematodes are small round worms. Entomopathogenic nematodes (also known as beneficial nematodes) are natural biopesticides. They kill insects pests but do not harm humans or the environment and so they are attractive alternatives to chemical insecticides. Some other kinds of nematodes are not beneficial; in fact some nematodes are serious pests of agricultural crops. For example, root knot nematodes are major pests of various crops such as peaches, pecans, soybeans, tomato, etc. The good nematodes (entomopathogenic nematodes) have been observed to suppress the bad nematodes including root knot nematodes. However, the mechanism behind the suppression is not known. In this study, we hypothesized that the beneficial nematodes repel root knot nematodes and therefore can "block" the bad nematodes from attacking plant roots. We discovered the hypothesis is true. Thus, beneficial nematodes repel root knot nematodes. The new information indicates that beneficial nematodes could be used to control root knot nematodes when the good nematodes are applied near plant roots.

Technical Abstract: Negative interactions in the rhizosphere between entomopathogenic nematodes and plant-parasitic nematodes, such as root-know nematodes, have been documented over the past two decades but the mechanisms and dynamics of such interactions remain largely elusive. Here, we evaluated the effect of inoculation position of two entomopathogenic nematode species, Steinernema feltiae and Heterorhabditis bacteriophora, as well as different facets of the symbiont complex on the migration of root knot nematodes toward tomato roots, both in sand and in Pluronic gel conditions. We show that when entomopathogenic nematodes were placed between the position of the root knot nematodes and the roots, the movement of root knot nematodes toward the roots is was inhibited. We observed this same pattern both in sand in in Pluronic gel and for both species of entomopathogenic nematodes. We also observed that different components of the symbiont complex (bacteria separate from the nematodes vs. the nematode-bacterium complex), and particularly the cell-free supernatant produced by the bacterial culture, displayed the highest inhibitory effect on root knot nematodes. By screening the for the most repulsive strains of entomopathogenic nematodes that are also effective against insect pests, combined target suppression it should be possible to alleviate biocontrol application costs in integrated pest management practices.