Interactions between the entomopathogenic nematode Heterorhabditis sonorensis (Nematoda

Heterorhabditidae) and the saprobic fungus Fusarium oxysporum (Ascomycota: Hypocreales)

P. D. Navarro, J. G. McMullen, S Patricia Stock

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

In this study, we assessed the effect of the saprobic fungus, Fusarium oxysporum (Ascomycota: Hypocreales) on the fitness of the entomopathogenic nematode Heterorhabditis sonorensis (Caborca strain). Sand column assays were considered to evaluate the effect of fungal mycelia on infective juvenile (IJ) movement and host access. Additionally, we investigated the effect of fungal spores on the nematodes' ability to search for a host, its virulence, penetration efficiency and reproduction. Three application timings were considered to assess interactions between the fungus and the nematodes. In vitro assays were also considered to determine the effect of fungal extracts on the nematode's symbiotic bacteria. Our observations indicate that presence and age of fungal mycelia significantly affect IJ movement in the sand columns and their ability to establish in the host. These results were also reflected in a reduced insect mortality. In particular, treatments with the 15. days old mycelia showed a significant reduction in insect mortality and penetration efficiency. Presence of fungal spores also impacted nematode virulence and reproduction. In particular, two of the application timings tested (simultaneous [EPN and fungal spores applied at the same time] and alternate I [EPN applied first, fungus applied 24. h later]) resulted in antagonistic interactions. Moreover, IJ progeny was reduced to half in the simultaneous application. In vitro assays revealed that fungal extracts at the highest concentration tested (10. mg/ml) inhibited the growth of the symbiotic bacteria. Overall, these results suggest that saprobic fungi may play an important role in regulating. EPN populations in the soil, and that they may be one of the factors that impact nematode survival in the soil and their access to insect hosts.

Original languageEnglish (US)
Pages (from-to)41-47
Number of pages7
JournalJournal of Invertebrate Pathology
Volume115
Issue number1
DOIs
StatePublished - Jan 2014

Fingerprint

Heterorhabditidae
Heterorhabditis
Hypocreales
entomopathogenic nematodes
Fusarium oxysporum
Ascomycota
nematode
Nematoda
fungus
fungal spores
nematode larvae
fungi
mycelium
application timing
spore
insects
insect
virulence
assays
sand

Keywords

  • Entomopathogenic nematode
  • H. sonorensis
  • Interactions
  • Saprobic fungus

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

Cite this

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title = "Interactions between the entomopathogenic nematode Heterorhabditis sonorensis (Nematoda: Heterorhabditidae) and the saprobic fungus Fusarium oxysporum (Ascomycota: Hypocreales)",
abstract = "In this study, we assessed the effect of the saprobic fungus, Fusarium oxysporum (Ascomycota: Hypocreales) on the fitness of the entomopathogenic nematode Heterorhabditis sonorensis (Caborca strain). Sand column assays were considered to evaluate the effect of fungal mycelia on infective juvenile (IJ) movement and host access. Additionally, we investigated the effect of fungal spores on the nematodes' ability to search for a host, its virulence, penetration efficiency and reproduction. Three application timings were considered to assess interactions between the fungus and the nematodes. In vitro assays were also considered to determine the effect of fungal extracts on the nematode's symbiotic bacteria. Our observations indicate that presence and age of fungal mycelia significantly affect IJ movement in the sand columns and their ability to establish in the host. These results were also reflected in a reduced insect mortality. In particular, treatments with the 15. days old mycelia showed a significant reduction in insect mortality and penetration efficiency. Presence of fungal spores also impacted nematode virulence and reproduction. In particular, two of the application timings tested (simultaneous [EPN and fungal spores applied at the same time] and alternate I [EPN applied first, fungus applied 24. h later]) resulted in antagonistic interactions. Moreover, IJ progeny was reduced to half in the simultaneous application. In vitro assays revealed that fungal extracts at the highest concentration tested (10. mg/ml) inhibited the growth of the symbiotic bacteria. Overall, these results suggest that saprobic fungi may play an important role in regulating. EPN populations in the soil, and that they may be one of the factors that impact nematode survival in the soil and their access to insect hosts.",
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