Genome characterization of Zucchini yellow mosaic virus infecting cucurbits reveals the presence of a new genotype in Trinidad & Tobago in the Caribbean region

Zucchini yellow mosaic virus is a potyvirus, which is becoming a serious pathogen of pumpkin and other cucurbits in Trinidad and Tobago and the entire Caribbean region. In this study, four Zucchini yellow mosaic virus (ZYMV) isolates infecting pumpkin in Trinidad and Tobago were characterized by complete genome sequencing for the first time. Phylogenetic analyses of the isolates showed variability of 5.9–6.0 % nt and 7.7–7.9 % aa sequences with the most closely related isolates NAT and AG (Israel) and SE04T (Slovakia). Based on the variations in complete genome as well as gene sequences, a new genotype designated ZYMV-Trini is proposed for these isolates. Among the gene sequences of ZYMV-Trini isolates, maximum variations were noticed in HC-Pro gene with 20.8 % aa sequence divergence from their closest relatives whereas the least variations were with the NIb, P3 and CP genes (1.8 to 2.2 % aa divergence). This study also proved that transmission of ZYMV can also occur through seeds (2 %), but this was less common than transmission via the aphid species Aphis gossypii. The progression of ZYMV in pumpkin seedlings was quantified by RT-qPCR which showed a rapid surge in viral load after 37 days. From the recombination analyses, it could be concluded that isolates SE04T from Slovakia, NAT from Israel and AG from Israel have major contributions in the genome architecture of ZYMV-Trini isolates.