Mitochondrial COI and cytb Characterisation of K-Lineage Varroa destructor Isolates From Kastamonu, Türkiye.

backgroundVarroa destructor is the most important ectoparasitic mite of the western honeybee (Apis mellifera) and remains a major threat to apiculture worldwide. Molecular characterisation of local mite populations is essential for understanding lineage composition and for establishing sequence-based epidemiological baseline data.

objectivesThis study aimed to determine the haplotypes and phylogenetic relationships of representative V. destructor isolates collected from Kastamonu Province in the Western Black Sea region of Türkiye using mitochondrial COI and cytb markers.

methodsA total of 100 adult female mites were collected from 10 locations, and one representative high-quality isolate from each locality (n = 10 per locus) was selected for bidirectional sequencing. Partial mitochondrial COI and cytb regions were amplified by PCR and sequenced. Consensus sequences were compared with GenBank records using BLASTn, and separate comparative datasets were constructed for each marker. Multiple-sequence alignments were generated with MAFFT, substitution models were selected with ModelFinder, and phylogenetic relationships were inferred using Maximum-likelihood and Bayesian approaches.

resultsAll sequenced Kastamonu representatives were completely identical within each marker, indicating mitochondrial homogeneity among the analysed isolates. In both the COI and cytb datasets, the study isolates clustered within the invasive K (Korean) lineage of V. destructor. In the COI analysis, the Kastamonu sequence grouped clearly with K-lineage references and separately from J-lineage sequences. The cytb analysis supported the same lineage assignment and likewise revealed no local mitochondrial subdivision within the sequenced representative subset. Comparative diversity analyses showed that, although the broader global datasets retained regional variation, the Kastamonu isolates analysed in this study were represented by a single mitochondrial background at both loci.

conclusionThe representative V. destructor isolates analysed from Kastamonu were identical at both mitochondrial markers analysed and belonged exclusively to the invasive K-lineage. These findings provide sequence-based confirmation of the maternal lineage detected among the sequenced mites and establish a regional molecular baseline for future surveillance of V. destructor populations in Türkiye. However, these findings should be interpreted within the limits of the representative sequencing design and should not be considered a definitive estimate of population-wide genetic diversity.