Fungal-feeding habits of six nematode isolates in the genus Filenchus

• Published in: Soil biology & biochemistry Vol. 37; no. 6; pp. 1113 - 1120
• Main Authors: Okada, Hiroaki, Harada, Hiroki, Kadota, Ikuo
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-06-2005; New York, NY Elsevier Science
• Subjects: Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chaetomium globosum; Chemical, physicochemical, biochemical and biological properties; Coprinus cinereus; culture media; Culture medium; Extraction efficiency; feeding behavior; Filenchus; Filenchus discrepans; Filenchus misellus; Flammulina velutipes; Food fungus; Fundamental and applied biological sciences. Psychology; Fungal-feeding; fungi; Fusarium oxysporum; in vitro studies; Nematoda; Nematode isolate; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Pleurotus ostreatus; population growth; Population growth rate; Pythium ultimum; Rhizoctonia solani; soil nematodes; Soil science; Tylenchidae; Culture medium; Fungal-feeding; Extraction efficiency; Food fungus; Tylenchidae; Filenchus; Nematode isolate; Population growth rate; Mycophagous; Fungi; Helmintha; Nemathelminthia; Population dynamics; Soil science; Invertebrata; Nematoda; Thallophyta
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2004.11.010

The family Tylenchidae is a large group of soil nematodes but their feeding habits are not fully known. We studied the fungal-feeding abilities of nematodes in the genus
Filenchus. We measured population growth rates (PGRs) of six nematode isolates, representing three
Filenchus species, when feeding on seven fungal species on two types of culture media. On Potato Dextrose Agar (PDA)
Filenchus misellus,
Filenchus discrepans and an unidentified
Filenchus sp. generally showed moderate to large PGRs on saprophytic fungi (
Rhizoctonia solani,
Chaetomium globosum,
Coprinus cinereus,
Flammulina velutipes) and low PGRs on plant-pathogenic fungi (
Fusarium oxysporum,
Pythium ultimum). In soil medium amended with chopped soybean plant material or wheat bran, the status of most of the fungi as food for the nematodes was similar to that on PDA, although PGRs tended to be lower in the soil medium. However,
C. globosum, a good food on PDA, only supported low PGR in soil for each of the three nematodes. The PGRs of
F. misellus on
C. globosum in soil were still low even when types and amounts of organic matter amendments were varied. A nematophagous fungus,
Pleurotus ostreatus (oyster mushroom), was determined to be a food for
Filenchus on PDA or in soil, based on PGR measurements corrected for extraction efficiency. To determine whether fungal species and culture media affected nematode extraction efficiencies and, consequently, the apparent PGRs, we compared efficiencies between
R. solani,
C. globosum and
C. cinereus, and between PDA and soil. The relatively low extraction efficiencies across fungal species in soil seemed responsible for the lower nematode PGRs in soil than on PDA. On PDA generally, fungal species did not affect the assessment. In soil, effects of fungal species on extraction were significant, but not consistent, across nematode species. Nevertheless, the extraction efficiency differences in soil were considered not to affect assessment of the three fungi as food for the nematodes. The confirmation that three
Filenchus species reproduce by feeding on fungi in soil suggests that fungal-feeding is not an unusual habit in the field, in this genus. We believe that in community studies, nematodes in the genus
Filenchus should be considered fungal feeders or root and fungal feeders, rather than only plant feeders. Our confirmation of fungal-feeding habits in the genus
Filenchus supports the hypotheses that plant-feeding nematodes evolved from those feeding on fungi.