Open Access

Matthias Preusche, Margot Schulz, Jakob Peter Ley, Andreas Ulbrich

• Some Hydrangea macrophylla/Hydrangea macrophylla subsp. serrata cultivars contain high amounts of the dihydroisocoumarins (DHCs) phyllodulcin and hydrangenol predominantly in young leaves. Treatments with methyljasmonate increases the contents as confirmed by studies with plants grown under optimized conditions. The functions of the DHCs for the plant are presently unclear. Since phyllodulcin has weak bactericide and moderate antifungal properties, bacterial and fungal endophytes of young leaves were isolated and PCR methods were used for identification. Most of the bacteria belong to the genus Bacillus. Other endophytes may belong to the genera Patulibacter, Rhodococcus, Rhizobium, Agrobacterium, Shouchilla, Priesta, Aeribacillus and Peribacillus, which is presently under conclusive proof, as are the endophytic fungal species belonging to the Ascomycetes. Culturing of several endophytes in presence of the DHCs revealed that some of the bacteria (Priestia spec., Patulibacter spec., Bacillus thuringiensis) and two fungi were able to degrade hydrangenol but not phyllodulcin. Ongoing studies with bacterial cultures point to growth modulation of some species by phyllodulcin. It is therefore hypothesized that phyllodulcin may have allelopathic functions in endophyte colonization success, as well as growth and microbial interaction control in the young leaves.