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Tylenchida Aphelenchina Aphelenchoidea Aphelenchidae Aphelenchus avenae
|Photograph: Wageningenen University|
|Aphelenchus avenae male tail: Spicules and bursa|
|Photomicrographs: Howard Ferris|
World-wide. Occurs in almost all soils.
Important in fungal-dominated decomposition channels.
Dish and column microcosms containing alfalfa-sand medium, two fungi (Rhizoctonia solani and Botrytis cinerea) and two nematodes (Aphelenchus avenae and Aphelenchoides composticola) were incubated at 15, 20, 25 and 29° C for 21 days.
In the dish microcosms, hyphal growth rates of both fungal species increased with temperature in the range of 15-25 ° C. Above that temperature range the growth rate of R. solani remained almost constant while that of B. cinerea decrease considerably. The population growth rate of A. avenae increased with temperature between 15 and 29 ° C on colonies of R. solani and B. cinerea in dish microcosms. The growth rate of A. composticola also increased in the range of 15-25 ° C but decreased greatly beyond that temperature range independent of the fungal species as food source.
Inorganic N (NH4+ + NO3-) was collected from each column microcosm by leaching every three days. In the columns containing R. solani, there was a significant effect of temperature on the amount of N detected in the fungus+A avenae or A. composticola but not in the fungus alone columns. The total amount of N was greatest at 29 ° C for A. avenae and at 20° C for A. composticola columns, concurrent with the population growth rates of the nematodes. In the columns containing B. cinerea the effect of temperature on the amount of inorganic N was not significant in either the fungus alone or fungus+nematode columns, although the population growth rates of the both nematode species were highest at 20° . For B. cinerea the N amount across temperatures was the same or larger for the fungus alone as for the fungus+nematode columns.
In general, the contribution of fungal-feeding nematodes to N mineralization was small in any combinations of fungus and nematode species at any temperature. Similarity in C/N ratio of the fungal and nematode biomass, organic substrate C/N ratios too low for measurable increase in net mineralization by the nematodes and small reproduction of the nematodes in the column microcosms were probable contributory factors (Okada and Ferris, 2001).
Aphelenchus avenae feeds on a variety of fungi (Giannakis and Sanders, 1989; Mankau and Mankau, 1963), but is not known to feed on higher plants (Hesling, 1977).
Males seem fairly common in some populations, less frequent in others.
Capable of withstanding dry conditions through anhydrobiosis. Used as a model system for studying anhydrobiosis.
Numbers are increased by addition of complex organic materials to soil to enhance fungal decomposition.
Giannakis N and Sanders F E 1989 Interactions between mycophagous nematodes, mycorrhizal and other soil fungi. Agric. Ecosyst. Environ. 29, 163-167.
Hesling J J 1977 Aphelenchoides composticola. In C. I. H. Descriptions of Plant-Parasitic Nematodes. Eds. S Willmott, P S Gooch, M R Siddiqi and M T Franklin. Set 7, No. 92. Commonwealth Agricultural Bureaux, Farnham Royal, Slough, U.K.
Mankau R and Mankau S K 1963 The role of mycophagous nematodes in the soil.Ⅰ. The relationships of Aphelenchus avenae to phytopathogenic soil fungi. In Soil Organisms. Eds. J Doeksen and J van der Drift. Pp 271-280. North Holland, Amsterdam, The Netherlands.
Okada, H., and H. Ferris. 2001. Temperature effects on growth and nitrogen mineralization of fungi and fungal-feeding nematodes. Plant and Soil 234:253-262.