[Antagonistic interactions between saprotrophic fungi and geohelminths. 1. Saprotrophic fungi in the biological control of phytopathogenic geohelminths].

Abstract

The state of knowledge on the possible antagonism between soil saprotrophic fungi and phytopathogenic nematodes of the genera Meloidogyne, Heterodera, and Globodera is reviewed basing on the literature and our own research. Mycelial colonisation of various developmental stages of these geohelminths is the most common factor thought to reduce their populations in nature. The following parasitic fungi can be found on the cysts, eggs, as well as the larvae of the nematodes: Paecilomyces lilacinus, Verticillium chlamydosporium, Cylindrocarpon destructans, Pochonia chlamydosporia, Fusarium spp., and Penicillium spp. The fungi invade the nematodes, such as Heterodera, Globodera, or Meloidogyne, "passively" penetrating through the natural orifices of the cysts, eggs, and larvae of the host. Equally frequent, however, is a biochemical action of the fungi prior to colonisation, which is linked with production of mycotoxirls or hydrolytic enzymes. Such an active way of fungal penetration of various stages of the phytopathogenic nematodes has been observed in Pochonia chlamydosporia, Penicillium verrucosum var. cyclopium, P. frequentans, Sclerotinia rolfsii, Rhizoctonia solani, and Fusarium spp. Triacylglycerols (TAG), phenols, as well as trichothecene, T-2, have been found in the metabolites extracted from mycelia of these species. Predation by fungi is also a factor that may reduce a population of phytopathogenic nematodes. This form of antagonism is characteristic for nematicidal fungi of the genera Arthrobotrys and Dactylella. These fungi form shrinking rings and hooks in their mycelia by which the fungus entangles and paralyses a migrating form of nematode. Despite the fact that the antagonism between fungi and nematodes is a commonly occurring phenomenon observed in the soil, the nematicidal and nematotoxic properties of fungi have not a wide application in biological plant protection. Up till now, only the bionematicides based on Arthrobotrys robusta (Royal 300 and Royal 350) as well as Paecilomyces lilacinus (Biocon and PL Plus) have found its commercial application.