Dissemination of Isaria fumosorosea Spores by Steinernema feltiae and Heterorhabditis bacteriophora.

Michal Kopačka,Jiří Nermuť,Vladimír Půža,Andrea Bohatá,Jana Konopická,Rostislav Zemek

doi:10.3390/jof6040359

Abstract

Entomopathogenic nematodes and fungi are globally distributed soil organisms that are frequently used as bioagents in biological control and integrated pest management. Many studies have demonstrated that the combination of biocontrol agents can increase their efficacy against target hosts. In our study, we focused on another potential benefit of the synergy of two species of nematodes, Steinernema feltiae and Heterorhabditis bacteriophora, and the fungus Isaria fumosorosea. According to our hypothesis, these nematodes may be able to disseminate this fungus into the environment. To test this hypothesis, we studied fungal dispersal by the nematodes in different arenas, including potato dextrose agar (PDA) plates, sand heaps, sand barriers, and glass tubes filled with soil. The results of our study showed, for the first time, that the spreading of both conidia and blastospores of I. fumosorosea is significantly enhanced by the presence of entomopathogenic nematodes, but the efficacy of dissemination is negatively influenced by the heterogeneity of the testing arena. We also found that H. bacteriophora spread fungi more effectively than S. feltiae. This phenomenon could be explained by the differences in the presence and persistence of second-stage cuticles or by different foraging behavior. Finally, we observed that blastospores are disseminated more effectively than conidia, which might be due to the different adherence of these spores (conidia are hydrophobic, while blastospores are hydrophilic). The obtained results showed that entomopathogenic nematodes (EPNs) can enhance the efficiency of fungal dispersal.

Highlights

Entomopathogenic nematodes (EPNs) of the families Steinernematidae Filipjev, 1934, and Heterorhabditidae Poinar, 1976, are ubiquitous soil organisms and can be found in almost all terrestrial ecosystems except for Antarctica
The main goal of this study was to evaluate the possibility of the dispersal of spores of the EPF I. fumosorosea by the entomopathogenic nematodes (EPNs) S. feltiae and H. bacteriophora
The nematodes were cultured in vivo in Galleria mellonella (Lepidoptera: Pyralidae) larvae, which were infected with ca. 50 infective juveniles (IJs) of the appropriate nematode per larva

Summary

Introduction

Entomopathogenic nematodes (EPNs) of the families Steinernematidae Filipjev, 1934, and Heterorhabditidae Poinar, 1976, are ubiquitous soil organisms and can be found in almost all terrestrial ecosystems except for Antarctica These nematodes live in obligate association with bacteria of the genera Xenorhabdus Thomas and Poinar, 1979, and Photorhabdus Boemare et al, 1993,. J. Fungi 2020, 6, 359 free-living stage is infective juveniles (IJs), which can detect hosts over long distances due to their sense organs. Fungi 2020, 6, 359 free-living stage is infective juveniles (IJs), which can detect hosts over long distances due to their sense organs They are able to react to many host-associated cues, such as carbon dioxide, arginine, uric acid, and ammonia [3,4,5,6,7]. The ability to actively search for hosts and rapidly kill them make EPNs good biocontrol agents

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