Endophytic fungus Beauveria bassiana can enhance drought tolerance in red oak seedlings

Endophytic fungi are known to be active in the plant environmental stress alleviation. In this work, we proved the ability of endophytic Beauveria bassiana, which is almost exclusively treated as an entomopathogenic fungus, in mitigating drought stress in dehydrated red oak (Quercus rubra L.) seedlings. Despite small differences between experiments, in general, leaf relative water content and stomatal conductance were less reduced (ca. 50% and 15%, respectively), free proline did not accumulate over the control level, carbon isotope C-13 discrimination/water use efficiency was not affected and root growth was stimulated at a similar plant transpiration area in the endophyte-colonised individuals. Regression analysis revealed that the root growth stimulation provided by the fungus under drought had the most important effect on their water status.