A new endophytic insect-associated Daldinia species, recognised from a comparison of secondary metabolite profiles and molecular phylogeny

Xylariaceous endophytes are commonly encountered in plants,and it has recently been found out that insect vectors play a major role in their life cycle,as well as in the apparent host-specificity of the fungal stromata.In this study,a new insect-associated,endophytic anamorph species of Daldinia is recognised from a comparison of (a)morphological and ecological data;(b)molecular phylogenetic data based on rDNA,alpha-actin and beta-tubulin genes;and (c)secondary metabolite profiles based on high performance liquid chromatography/diode array/mass spectrometry(HPLC-DAD/MS)and gas chromatography/mass spectrometry(GC-MS)in comparison with authentic strains of Daldinia and other Xylariaceae.The new species,Daldinia hawksworthii,is a symbiont of the willow woodwasp,Xiphydria prolongata,which is in turn preferentially associated with Salix.A comparison of HPLCDAD/MS profiles from standardised cultures revealed the presence of a specific compound,which was not encountered in any of the ca.250 Daldinia strains studied for comparison.This compound was isolated after fermentation of the fungus in 10 l scale by preparative chromatography.Structure elucidation by NMR spectroscopy revealed a novel pyrone,for which the name dalsymbiopyrone is proposed.The compound showed weak antimicrobial and cytotoxic effects and might be a signal molecule involved in the trilateral ecological interaction between the host plant,the insect,and its fungal symbiont.