Mycorrhizal colonisation of highbush blueberry and its native relatives incentral Finland

Transmission electromicroscopy, trypan blue staining in combination with st ereomicroscope analysis and biochemical ergosterol assay were used to study the mycorrhizal symbionts in wild bilberry (Vaccinium myrtillus), bog whor tleberry (Vaccinium uliginosum) and highbush blueberry (Vaccinium corymbosu m) roots. TEM-analysis showed that in all species cricoid mycorthizas forme d hyphae coil inside the epidermal root cells. In stereomicroscopic viewing the highest mycorrhizal colonisation was observed in the roots of wild bil berries (51%), whereas according to the ergosterol assay the highest total fungal biomass of roots was found in bog whortleberries (209 mug g(-1) of r oot d. wt). Both ergosterol and microscopical method showed that the mycorr hizal associations in blueberry cultivars and their wild relatives growing on natural soil medium are frequent, although ericoid mycorrhiza formation of highbush blueberries was somewhat weaker than that of wild bilberries an d bog whortleberries.