Dendrogram showing the relationship of the Beta vulgaris chromoviruses to other chromodomain-containing Ty3- gypsy retrotransposons. The neighbor-joining tree was constructed from the alignment of the complete gag-pol polyprotein sequences of B. vulgaris and representative chromoviruses from other plant genomes (CRM, Tekay, and Reina from Zea mays, Galadriel from Lycopersicon esculentum). For further classification, the recently described Ty3-gypsy retrotransposon TRRT1 (tomato ribosomal (r)DNA-related retrotransposon) was included. The fungi and vertebrate chromoviruses from Magnaportha grisea (Maggy) and Takifugu rubripes (Sushi-ichi) were included as outgroup elements to root the tree. Bootstrap values are indicated as a percentage of 1,000 replicates.