Temporal infectivity and specificity of vesicular-arbuscular mycorrhizas in co-existing grassland species.

Specificity in vesicular-arbuscular mycorrhizas (VAM), arising from selection favouring host plant/mycorrhizal fungus associations in which both organisms receive benefit, might have a significant influence on interactions between co-existing plant species. In an attempt to detect such specificity root inoculum of four tempt to detect such specificity root inoculum of four plant species, harvested from a species-rich grassland on three dates during the plant growth season, was used to infect the same plant species grown in pots. The rate and overall level of infection was different according to inoculum source and the time of year in which the inoculum was harvested, i.e. temporal variation in VAM infectivity occurs. However, there was no evidence for either specificity or mycorrhizal benefit. Inoculum produced during this experiment was used to infect "bait" Trifolium pratense plants and protein patterns of these roots indicated that a number of biochemically different endophytes were present, both within the inoculum of the four plant species but also within inoculum from one plant species. Temporal variation in mycorrhizal infectivity could be important for mycorrhizal propagation in the field. However, the lack of evidence, in this study, for specificity of VAM or an obvious nutritional benefit to plants with mycorrhizas make the role of mycorrhizas in this community difficult to interpret.