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1. The fungus Neotyphodium lolii forms a symbiotic relationship with its grass host Lolium perenne (perennial ryegrass). The fungus benefits from access to plant nutrients and photosynthate, whereas the plant benefits from acquired chemical defence against herbivory.2. This study examined the potential for endophyte-mediated plant defences to influence interactions between fall armyworm Spodoptera frugiperda, and the entomopathogenic nematode Steinernema carpocapsae and clarified biological mechanisms underlying the observations made.3. In laboratory and greenhouse experiments, S. frugiperda larvae were fed endophytic or non-endophytic L. perenne then exposed to S. carpocapsae or injected with the nematodes' symbiotic bacteria Xenorhabdus nematophila.4. In all instances, S. frugiperda larvae fed endophyte-infected grass suffered significantly lower mortality than those fed non-endophytic plants. Although larvae fed endophyte-infected grass often had significantly lower biomass than those fed uninfected grass, these differences did not account for altered susceptibility to S. carpocapsae.5. Endophyte-mediated reductions in herbivore susceptibility to the nematode pathogen represent a herbivore adaptation that effectively turns the tables on both plant and natural enemy by reducing the virulence of the nematodes' symbiotic bacteria while expanding the temporal window of herbivory.

Summary 1.There is growing awareness that biological control carries risks as well as benefits, but there are few data on below-ground effects of inundative insect pathogens. We addressed this issue using entomopathogenic nematodes and the soil nematode community in a turfgrass ecosystem as a model. 2. Application of Heterorhabditis bacteriophora strain GPS11, Heterorhabditis bacteriophora strain HP88 and Heterorhabditis indica strain LN2 significantly reduced the abundance, species richness, diversity and maturity of the nematode community by reducing the number of genera and abundance of plant-parasitic, but not free-living, nematodes. 3. Our results are the first to indicate selective suppression of plant-parasitic nematodes by entomopathogenic nematodes, H . bacteriophora and H. indica , with no adverse effect on free-living nematodes. 4. In contrast to the entomopathogenic nematode treatments, trichlorfon (a commonly used insecticide in turfgrass) reduced the number of genera, abundance and diversity of the nematode community by adversely affecting both plant-parasitic and free-living nematodes. 5. The reduction in abundance and diversity of plant-parasitic nematodes without any adverse effect on free-living nematodes that play a role in nutrient cycling, can be considered as a beneficial non-target effect of entomopathogenic nematodes. The mechanisms causing such an effect need to be elucidated in future studies.

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In Arabidopsis, non-expressor of pathogenesis related genes-1, NPR1 has been shown to be a positive regulator of the salicylic acid controlled systemic acquired resistance pathway and modulates the cross talk between SA and JA signaling. Transgenic plants expressing AtNPR1 constitutively exhibited resistance against pathogens as well as herbivory. In the present study, tobacco transgenic plants expressing AtNPR1 were studied further for their response to infection by the sedentary endoparasitic root knot nematode, Meloidogyne incognita. Transgenic plants showed enhanced resistance against the root-knot nematode infection. Prominent differences in the shoot and root weights of wild type and transgenic plants were observed post-inoculation with M. incognita. This was associated with a decrease in the number of root galls and egg masses in transgenic plants compared to WT. The transgenic plants also showed constitutive and induced expression of some PR protein genes, when challenged with M. incognita.

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