Molecular and Evolutionary Characterization of Wild Yeast Isolates from Banana Fruit and Honey Relative to a Commercial Wine Yeast using Statistical Phylogenetic Tools

Abstract

Wild yeast isolates from banana fruit and honey were compared with a commercial wine yeast using partial ITS1–5.8S–ITS2 sequences and statistical phylogenetic analyses in MEGA 12. Five sequences representing banana isolates B7 and B10, honey isolates H4 and H7, and commercial yeast CY were evaluated for BLASTN affinity, evolutionary divergence, nucleotide composition, substitution-pattern homogeneity, neutrality statistics and relative-time relationships. BLASTN provisionally associated B7, B10, H4 and CY with Candida tropicalis and H7 with Clavispora lusitaniae; however, sequence identities of 77.6–95.0% were below the stated ITS thresholds for reliable species- and genus-level assignment. H4 and B10 showed the closest relationship, with divergence of 0.011 ± 0.005 substitutions per site, 100% bootstrap support and identical EcoRI profiles. The remaining pairwise distances ranged from 0.401 to 0.690 substitutions per site. The alignment was AT-rich (58.47%) and strongly transition-biased (R = 17.255), while disparity-index testing did not detect significant substitution-pattern heterogeneity among sequence pairs. Tajima’s D was 0.302 and is interpreted descriptively because the alignment spans more than one taxonomic group and includes only five sequences. Overall, the analyses support provisional molecular characterisation of the isolates but do not provide secure species-level identification. Re-verification of sequence quality and multilocus analysis are therefore required before definitive taxonomic interpretation.