Nematophagous fungi in the rhizosphere of agricultural crops
In a field experiment the rhizosphere effect of barley, pea and white mustard on the nematode-trapping fungi were investigated throughout a growing season. The densities of nematode-trapping fungi were slightly increased in the rhizospheres compared to the root-free soil. Pea rhizosphere had the greatest numbers of species of nematophagous fungi with an average of 2.4 species recovered from 0.1 g material, and in white mustard and barley rhizospheres and root-free soil less than 1.7 species were recovered from 0.1 g. Arthrobotrys oligospora was the most common species in both soil and rhizosphere. In a pot experiment the rhizosphere effect of pea and barley on nematophagous fungi was investigated in 5 different agricultural soils. Pea rhizosphere increased the densities of nematode-trapping fungi, and up to 780 propagules of nematode-trapping fungi g−1 rhizosphere soil were found, which was around 19 times higher than in the root-free soil. The number of nematodes were 6–290 times higher in the pea rhizosphere than in the root-free soil. Barley rhizosphere had little effect on the densities of nematode-trapping fungi, while the number of nematodes increased by 3–13 times. The most commonly detected species were A. oligospora, Stylopage sp. and network-forming Monacrosporium species, but there were no big differences in the species composition between the rhizosphere and the root-free soil.