*3.1. General Experimental Procedures*

NMR spectra were recorded on a Varian 400 MHz and/or Varian 600 MHz spectrometer (Varian, Palo Alto, CA, USA ) using CDCl3 or CDCl3/methanol-*d*<sup>4</sup> (4:1) as the solvent, unless otherwise stated. MS analyses were performed on an Agilent Series 1100 SL equipped with an ESI source (Agilent Technologies, Palo Alto, CA, USA). Column chromatography was carried out on silica gel 60 (230–400 mesh) (Sigma-Aldrich, St. Louis, MO, USA) and Sephadex LH-20 (105 × 3 and 69 × 2 cm2) (GE Healthcare Bio-Science, Marlborough, MA, USA). HPLC analysis was carried out on a Hewlett Packard 1100 series instrument with Luna C18 columns (10<sup>μ</sup> C18 <sup>250</sup> × 4.6 mm2, 10 micron; 10<sup>μ</sup> C18 <sup>250</sup> × 2 mm2, 10 micron; Phenomenex (Torrance, CA, USA) as the stationary phase and methanol-water (1:4) as the mobile phase. TLC spots were detected under UV light and by heating after spraying with anisaldehyde reagent.

#### *3.2. Isolation of the Fungus from a Seed of Diseased T. taxifolia*

Seeds were collected from a *T. taxifolia* tree with disease symptoms cultivated on the Biltmore Estate in Asheville, North Carolina. A voucher of the *T. taxifolia* Arn. plant was identified by E. M. Croom, Jr. and deposited in the University of Mississippi Pullen Herbarium. The voucher accession number is MISS 55406.

A seed of *T. taxifolia* was surface disinfected by immersing in 70% EtOH (1 min) and 2% NaOCl (3 min), followed by washing with sterile distilled water (2 min). The seed was subsequently fragmented and plated onto Petri dishes containing potato dextrose agar (PDA; BD Difco, Franklin Lakes, NJ, USA) supplemented with 200 mg/L chloramphenicol to avoid bacterial contamination. The plates were incubated at 25 ◦C for 60 days. Hyphal growth was monitored over an 8-week period. Using an aseptic technique, the endophyte was transferred to PDA contained in 60-mm Petri plates. The long-term preservation of filamentous fungal colonies was carried out in cryotubes containing 15% sterile glycerol at −80 ◦C.

#### *3.3. Identification of the Fungus by DNA Analysis*

DNA isolation, PCR amplification, cloning, and sequencing were performed as described in Kumarihamy et al. 2019 [12]. Homology searches were performed with the Basic Local Alignment Search Tool (BLAST) [40]. The UM124 sequence was submitted to GenBank (Accession MK679616).

A phylogenetic tree [12] was constructed to identify close relatives of UM124 with the best 19 hits from BLAST and already published sequences in Genebank of various *Botryosphaeria* species. In addition, a phylogenetic tree of UM124 and sequences from various taxa of the family *Botryosphaeriaceae* was constructed (Supplementary Materials: Tables S1 and S2 and Figures S1 and S2).
