On the use of sodium hexametaphosphate to extract spores of arbuscular mycorrhizal fungi from soil

Extraction of arbuscular mycorrhizal fungal (AMF) spores from soil is widely used to assess AMF community structure and abundance. The most widely used protocol relies on a water-sucrose gradient flotation technique. Na-hexametaphosphate has also been used to deflocculate soil aggregates prior to spore extraction in order to optimize recovery, but its effect on spore viability remains unknown. Here, we report that Na-hexametaphosphate increases average spore yield in a high clay soil by about 15%, but decreases average spore viability by about 20%. Na-hexametaphosphate should therefore be used cautiously where the extracted spores are destined to be used as inoculum for subsequent studies.