The use of fatty acid signatures to study mycelial interactions between the arbuscular mycorrhizal fungus Glomus intraradices and the saprotrophic fungus Fusarium culmorum in root-free soil

The saprotrophic fungus Fusarium culmorum, Penicillium hordei, Rhizoctonia solani and Trichoderma harzianum and the arbuscular mycorrhizal fungus Glom us intraradices were examined for content of phospholipid fatty acids (PLFA ) and neutral lipid fatty acids (NLFA). The AM fungus differed from the sap rotrophic fungi especially by its content of the fatty acid 16:1 omega 5 wh ich was absent in the saprotrophs. The fatty acid 18:2 omega 6,9 was the do minant fatty acid of the saprotrophic fungi while it was negligible in myce lium of G. intraradices. Specificity in content of fatty acids made it poss ible to quantify G. intraradices. and F. culmorum simultaneously in soil. F urthermore, a compartmented growth system made it possible to study mycelia l interactions in the absence of roots. We measured hyphal spread of both f ungi, hyphal P-33 transport of G. intraradices and sporulation of F. culmor um. The two fungi did not interact according to the parameters used in this study. We conclude that fatty acid signatures may be a valuable tool when studying interactions between AM fungi and other fungi in root-free soil.