Nematode Trapping Fungi 4211 Introduction

As the name of this group implies, they are soil-borne fungi that entrap moving stages of nematodes using trapping structures of various shapes and sizes. These fungi are not host specific and could trap all soil-dwelling nematodes. Different fungal species produce one or more types of different trapping devices. These structures can vary from simple fungal hyphae covered with sticky secretions (Stylopage spp.) to much more complex structures. They can be adhesive branches, simple loops, two-dimensional, or three-dimensional networks. Adhesive three-dimensional nets, the most common type of fungal traps, are constructed when the loops create a three-dimensional configuration (e.g. Arthrobotrys oligospora, A. superba, Dactylellapseudoclavata). Other groups of trapping fungi produce adhesive spores (Meristacrum spp.) or adhesive knobs (A. haptotyla, Nematoctonus spp.). Lateral branches of vegetative hyphae create non-constricting rings which entrap the entering nematodes by wedging around their body. Constricting rings (Arthrobotrys dactyloides, Monacrosporium doedycoides) are the most specialized trap, which has three cells that swell quickly and hold the entering nematode tightly [3, 11, 16, 49].

Trapping structures may differ even within a genus, for example Nematoctonus robustus produce adhesive knobs exclusively on hyphae, N. leptosporus exclusively on germinated conidia, and N. angustatus on both hyphae and conidia [50].

Some disadvantages like complexity in the establishment in the soil, their limited capturing activity and above all non-specific trap of plant-parasitic nematodes reduce their potential in biological control. Some Arthrobotrys species have been formulated and applied under specific conditions, but the results were inconsistent [11].

It was proved that trapping fungi also have the ability of secretion antimicrobial and nematicidal compounds like linoleic acid (A. oligospora, A conoides) or pleurotin (N. robustus, N. concurrens). The production of linoleic acid was positively correlated with the number of traps formed [51].

Table 4.2 Extracellular enzymes isolated and characterized from different nematophagous fungi (Modified from [16])

Enzymic group

Fungal group

Enzyme name

Origins

References

Serine proteases

Nematode-trapping fungi

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