The soil bacterium Lysobacter capsici attaches to the nematode surface, and triggers induced systemic resistance in barley, impairing the invasion of root-lesion nematodes

Root-lesion nematodes pose a global threat to crop yield and stability,
with their broad host range presenting a formidable challenge for
effective management. In this study, we investigated the role of the
nematode-attached bacterium Lysobacter capsici in mitigating the invasion
of Pratylenchus penetrans into spring barley roots. Using a split-root
system, we demonstrated that the cuticle-attached bacterium significantly
reduced nematode invasion by 75% to 77% as compared to the nematodes
without L. capsici. This reduction was predominantly due to the induction
of systemic defense in the plants, and partially due to the
bacterium's local antagonism in contact with the nematode.Compared to
the nematodes without L. capsici, the reduced root invasion of P.
penetrans with attached bacteria differed over time and was particularly
observed at 48- and 72 hours post-inoculation. Notably, the reduction in
nematode invasion was more pronounced when L. capsici cells were attached
to the nematode cuticle than when the bacteria were applied systemically
and were not directly interacting with the nematodes. In addition,
transcriptional analyses revealed a higher expression of the barley
pathogenesis-related gene PR1 in response to the nematodes with attached
bacteria compared to the surface-sterilized nematodes or L. capsici cells.
This suggests that nematodes carry bacteria inside the roots that activate
plant defense. Our study showed the potential of L. capsici to effectively
manage nematode populations and improve plant health by inducing the plant
immune system upon nematode invasion.