Influence of climate zones on the genetic diversity of cucumber mosaic virus isolates

Introduction. Cucumber mosaic virus (CMV), a positive-sense single-stranded RNA plant virus of the Bromoviridae family, is one of the most economically important viruses affecting cucurbit crops worldwide. Its global distribution indicates extensive adaptive features at the genomic level. The aim of this study was to examine the genetic variability of the coat protein gene nucleotide sequences in CMV isolates originating from different climatic regions.

Methods. The nucleotide sequences of the CMV coat protein were downloaded from the NCBI Virus database selecting isolates from five climate zones (subpolar, temperate, subtropical, tropical, and equatorial). The sequences were processed using the MEGA11 software package.

Results. A total of 55 isolates from five climatic zones were analyzed. The results revealed a high degree of intragroup variability in coat protein gene sequences represented by deletions/insertions, single- or multiple-nucleotide polymorphic sites. Variable sites accounted for 63%, parsimony-informative sites for 50%, singleton sites for 13%. The highest intragroup variability was detected among isolates of tropical zone (0.65), the lowest was observed in equatorial and subtropical zones (0.076). The intergroup heterogeneity index was greatest between isolates from tropical and subpolar zones (0.55) and lowest between equatorial and subtropical zones (0.09). Phylogenetic analysis showed clustering into the recognized CMV subgroups I and II, whereas isolates did not segregate according to climatic origin.

Conclusions. The results demonstrate the influence of climatic environments on the genetic variability of CMV, providing valuable insights into the genetic organization of the virus, although evolutionary history likely plays a dominant role.