## 3 Results
### Sea-Buckthorn-Associated Cultivable Potential Biocontrol Yeasts and Their Produced Volatiles  
By applying cultivation techniques, more than 20 yeast strains were isolated from the surface of sea buckthorn berries. Yeasts were subjected for primary species identification by morphological colony analysis and bright field microscopy with following fingerprinting of PCR-amplified sequences of internal transcribed spacers 1 and 2 including 5.85 ribosomal RNA gene. For further analysis of VOC production, selected strains proceeded sequencing-based species level confirmation and deposition of sequences in NCBI. Four yeast strains, belonging to different genera identified by metagenomics analysis of UB and RB microbiota with referred potential biocontrol properties [15; 16; 40] (Table S1, Figure 5), were selected for VOCs analysis. Morphologically different SB-18-2 and SB-18-25 yeast strains were recovered from UB berries while SB-18-34 and SB-18-31 yeast strains were isolated from RB berries. Basing on the electrophoretic analysis, similar size (about 600 bp) ITS regions were PCR-amplified from SB-18-2 and SB-18-25 strains, and differed in _Hirfl_ and _Cfol_ restriction patterns (Figure 5). The sequence identity  
Figure 4: Heatmap of fungal microorganism’s unique amplicon sequence variants (ASVs) abundance on sea buckthorn. The color intensity is proportional to the relative abundance of fungal microorganism ASVs. match of SB-18-2 yeast was 99.64%, comparing to that of _Aureobasidium pullulans_ culture YY11 deposited in GenBank. SB-18-25 yeast strain was assigned to _Cryptococcus wieringae_ (syn. _Filobasidium wieringae_) basing on RFLP profile and 99.48% similarity to _C. wieringae_ CBS:11709 culture. Following the genomic DNA purification, 380 bp and 700 bp PCR products were amplified from SB-18-34 and SB-18-31 yeast strains, respectively. Their PCR-RFLP profiles corresponded to _Metschnikowia_ and _Hanseniaspora_ yeast species [41]. According to the high similarity to sequences depositedin GenBank, SB-18-34 strain was identified as _Metschnikowia pulcherrima_ and SB-18-31 as _Hanseniaspora warum_ yeast species (Figure 5). _Aureobasidium pullulans_ SB-18-2 belongs to genus, which is the most abundant in UB samples (31.4%), and of significant representation (40.6%) in RB samples. _Metschnikowia pulcherrima_ SB-18-34 represents genus, which is the most abundant (44.5%) in RB samples. _Cryptococcus wieringae_ SB-18-25 belongs to genus, more prevalent (1.9%) on the surface of UB berries than on the RB berries (0.2%). _Hanseniaspora warum_ SB-18-31 is a member of genus, which is the least dominant among the selected genera with only 0.5% and 0.2% occurrence in UB and RB samples, respectively. The gas chromatographic-mass spectrometric analysis revealed 29 compounds that were exclusively present in the headspace of four yeast species and occurred significantly more abundant compared to those of control samples. The yeast released volatiles were composed of 11 esters, 6 alcohols, 5 volatile fatty acids, 3 ketones, 2 aromatics, and 2 compounds bearing both ester and aromatic moieties (Table 2). Figure 5: Identification of yeasts isolated from sea buckthorn surface.