Effect of cropping pattern and green manure on the antagonistic potential and the diversity of egg pathogenic fungi in fields with Heterodera schachtii infection

The potential of egg pathogenic fungi in soil from two different sites infe sted with Heterodera schachtii was measured with a new method in pot experi ments. The potential proved to be much greater in the rotation field (sugar beet-wheat) than in the monoculture held (mangold). The green manuring wit h three different intercrops reduced the potential in soil from the rotatio n field and promoted it in the monoculture field. Investigation on the dive rsity of egg pathogens in the two fields showed that the monoculture held h ad a greater diversity than the rotation field. A large fungal diversity is thought to act as a buffer against microbial changes. This is probably a r eason why green manuring in the monoculture field did not reduce this funga l diversity as markedly as in the rotation field and why it did not reduce the potential of egg pathogenic fungi in the same held.