Influence of water stress on biomass production by isolates of an ericoid mycorrhizal endophyte of Woollsia pungens and Epacris microphylla (Ericaceae)

The influence of water stress on growth of six isolates of an anamorphic ericoid mycorrhizal fungal endophyte from two Australian Ericaceae hosts was investigated. Biomass production was determined in liquid media amended with NaCl or polyethylene glycol to give osmotic potentials of -0.05 to -2.24 MPa. Regardless of the osmoticum, biomass yields of all isolates at the highest level of imposed water stress (-2.24 MPa) did not differ significantly from, or were significantly higher than, those at the lowest level of water stress. The data suggest that the endophyte isolates possess considerable resistance to water stress and may be of functional importance to their plant hosts under water-stress conditions.