Treatment of soil with nematicides
is considered an essential means of off-setting severe economic losses due to nematodes.
However, there is worldwide concern over the impact of nematicides on non-target
populations, ground water contamination, and air pollution. Consequently, the need for
non-chemical approaches for nematode control is urgent.
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Root
colonized by arbuscular mycorrhizal fungus |
Arbuscular mycorrhizal (AM) fungi and plant parasitic nematodes are inhabitants
of plant roots and often interact with each other. Since the prevailing aspect of this
interaction is the suppression of nematodes by the fungi, we have been conducting research
aimed at developing strategies for managing AM fungi as biological control agents against
plant parasitic nematodes.
One of the findings of our investigation is that the effectiveness of AM fungi in
suppressing plant parasitic nematodes could vary from very low to very high depending on
the plant species, nematode species and the AM fungal species involved. Of the arbuscular
mycorrhizal fungi we evaluated the species that was most consistently effective in
suppressing plant parasitic nematodes was Glomus mosseae. Under controlled
conditions, this species protected papaya against damage by the plant parasitic nematode Meloidogyne
javanica to the extent of 37 %. Similarly, the fungus reduced damage of white
clover caused by M. incognita by 68%. There were fewer nematodes in roots of papaya
and white clover in the presence of G. mosseae than in its absence.
At least in white clover, the effect of AM fungi in suppressing nematodes cannot be
duplicated by increasing the concentration of phosphorus in soil. The mechanism by which
AM fungi suppress plant parasitic nematodes, therefore, does not appear to be related to
enhanced nutrient uptake of associated plants by the fungi.
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