Observations on Antagonism in the Arbuscular Mycorrhizal Systems

The majority of land plants are colonised by arbuscular mycorrhizal fungi, however ,members of few families notably Cruciferae, Chenopodiaceae, Caryophyllaceae and Polygonaceae, so called non-host are not colonized by these fungi. Previous studies have shown that the growth and development of non-host species were severely inhibited when grown in the presence of active AMF mycelia. There is therefore a need to understand the mechanistic bases of adverse effects of AMF mycelia upon seedlings of non-host species. In this experiment young roots of non-hosts Spergula arvensis and Arabis hirsuta, and host Centaurium erythraea were exposed to mycorrhizal and non-mycorrhizal extracts. The results of this experiment showed that mycorrhizal extracts significantly reduced the growth of radicles and root hairs development of non-host species whereas had no effect on radicles and root hairs development of host species. These results indicate that toxicity effects rather the nutritional factors are the drivers of the negative responses of non-host species to the presence of the AMF. Keywords: mycorrhizal fungi, host and non-host plants, Plantago lanceolata , Glomus mossae , mycelium