Bioactivity and genetic diversity of endophytic fungi in Rhododendron tomentosum Harmaja

Eighty-seven endophytic fungi were isolated from asymptomatic leaf tissues of Rhododendron tomentosum. Most of the isolates were non-sporulating and therefore difficult to identify exclusively based on morphological characters. Eighteen isolates that were morphologically distinct were selected for identification by sequencing the ITS region. For culture-independent analysis, the DNA was isolated from the surface-sterilized leaves of R. tomentosum and the ITS region was amplified using fungal specific primers ITS1F and ITS4, cloned, and 11 clones were randomly selected and sequenced. The phylogenetic analysis was performed with MEGA4 on a total of 49 sequences, including 18 endophytic isolates and 11 unculturables obtained in this study, and 20 sequences from Genbank, which were distributed in four clusters. The culturable and unculturable endophytes formed separate clades and were clearly distinguishable with no overlap within the groups. Endophytic fungi are a well-recognized source of bioactive compounds and therefore antibacterial and antioxidant activities of the isolates of R. tomentosum were studied. All isolates were grown in two different media, enriched (MEB) and depleted (DM), and screened for antibacterial and antioxidant activities. As a result, 10% produced antibacterials and 14% antioxidants, in total 24% of the isolates had biological activity. Antioxidant broth of TRT59 was partially purified using HPLC. The majority of antibacterial compounds were produced in DM media and antioxidants in MEB media. Therefore, it is advisable to test various media for production of antibacterials and antioxidants.