Genetic Diversity of Potyviruses Associated with Tulip Breaking Syndrome

Tulip breaking is economically the most important viral disease of modern-day tulip growing. It is characterized by irregular flame and feather-like patterns in the flowers and mosaic on the foliage. Thirty-two leaf samples were collected from cultivated tulip plants showing tulip breaking syndrome from Hungary in 2017 and 2018. Virus identification was performed by serological (ELISA) and molecular (RT-PCR) methods. All samples proved to be infected with a potyvirus and evidence was provided that three potyvirus species could be identified in the samples: Lily mottle virus (LMoV), Tulip breaking virus (TBV) and Rembrandt tulip-breaking virus (ReTBV). Recombination prediction accomplished with Recombination Detection Program (RDP) v4.98 revealed potential intraspecies recombination in the case of TBV and LMoV. Phylogenetic analyses of the coat protein (CP) regions proved the monophyletic origin of these viruses and verified them as three different species according to current International Committee on Taxonomy of Viruses (ICTV) species demarcation criteria. Based on these results, we analyzed taxonomic relations concerning potyviruses associated with tulip breaking syndrome. We propose the elevation of ReTBV to species level, and emergence of two new subgroups in ReTBV.