What do root pathogens see in mycorrhizas?

Refined understanding of the exchanges of P, C and other nutrients in arbuscular mycorrhizas and the mycorrhizosphere permits us better to answer the question 'what do root pathogens see in mycorrhizas?' Larsen and Bodker (1994) employ neutral lipid fatty acids for more precise quantification of the interaction of a root pathogen and an AM fungus than here-to-fore possible. Moreover, these fatty acids give estimates of the 'energy status' of the interacting fungi, as the signature acids comprise more than 50% of the storage lipid in each fungus. The concomitant reduction in each fungus's biomass and energy status provides preliminary evidence for competition for resources between the obligate symbiont and the biotrophic pathogen. The specificity of signature fatty acids for evaluation of direct interactions of selected microbes and plant species should greatly facilitate studies, particularly under field conditions.