Epidemiological patterns for viruses infecting vegetable crops based on their molecular and biological properties were discovered. New virus sources, routes of transmission and susceptible hosts were described for artificial ecosystems. Molecular typing and evaluation of epidemic potential were carried out for the established spectrum of harmful viruses endangering commercial production of vegetable crops in Ukraine comprising viruses belonging to the families Virgaviridae (PMMoV, ToMV, CGMMV, TRV), Bromoviridae (CMV), Potyviridae (PVY, ZYMV, WMV-2, TuMV) and Alphaflexiviridae (PVX). PMMoV, PepMoV and TuMV were described in Ukraine for the first time.
Significant portion of mixed virus infection was shown which were typically induced in Ukraine by the following virus groups: ZYMV/WMV-2, CMV/ZYMV/WMV-2, CMV/ToMV/PVY and TuMV/CMV. It was established that seeds of vegetable crops was one of the important and often neglected source of viruses in the ecosystems. For Ukraine, seed transmission was confirmed as an important way of spread of many viruses (CGMMV, ZYMV, ToMV and CMV) requiring special control for pathogens with wide host range (CMV and ToMV).
Biological properties of Ukrainian virus isolates (ToMV, TuMV, CMV, etc.) were confirmed to correlate with their respective genetic characteristics in the context of virulence toward vegetable crops. Ukrainian populations of WMV-2, ZYMV, PMMoV and ToMV were mainly genetically homogenous with high (>90%) degree of identity to known isolates and strains of respective viruses. Unique amino acid substitutions in the 2b protein were found for Ukrainian isolates of CMV suggesting higher level of genetic heterogeneity of its population in Ukraine. It was demonstrated that phylogenetic relationships of Ukrainian isolates of viruses infecting vegetable crops were not dependent on geographical origin of the isolates or their host plant.
Novel recombinants of harmful viruses WMV-2 and TuMV were found suggesting intense exchange of viral genetic material and evolutionary processes in Ukraine and posing epidemiological risks. Analysis of the full-genome sequence of Ukrainian TuMV isolate showed that isolate UKR9 has not been described before and was an atypical European recombinant combining traits of two different genetic groups World-B and Asian-BR.
Following the molecular typing of viruses, a full genomic and 33 partial genetic sequences of Ukrainian isolates of viruses infecting vegetable crops were deposited to the Genebank (NCBI) constituting over 25% of all plant viral sequences published from Ukraine.
Urban ecosystems together with their concomitant wild-growing and cultural flora were demonstrated as important factors maintaining populations of viruses infecting vegetable crops.
Based on the complex of biological and molecular epidemiological features it was construed that ToMV, TuMV and CMV were potentially the most harmful viruses endangering cultivation of vegetables in Ukraine.
The concept for reliable and cost-effective control of viruses infecting vegetable crops in Ukraine was elaborated basing on epidemiological properties of viruses, type of susceptible crop(s) and the environment.
