Molecular characterization and infectious clone construction of beet capulavirus 1 infecting tomato in Germany

Capulavirus betae (beet capulavirus 1, BCV1) is a recently described species of the genus Capulavirus (family Geminiviridae) that was first identified in sugar beet in France. Capulaviruses are new group of geminiviruses because they are transmitted by aphids. Here, we report the identification and molecular characterization of an isolate of BCV1 infecting cultivated tomato in Germany and describe the construction of an infectious clone. In August 2025, tomato plants displaying severe virus-like symptoms, including leaf deformation, leaf curling, stunting and chlorosis were collected from two production sites in North Rhine-Westphalia. High-throughput RNA sequencing revealed a single viral contig representing a complete circular DNA genome with 99.5% nt identity to BCV1. The presence of the virus was additionally confirmed in five out of six individual tomato samples by specific PCR. Rolling-circle amplification (RCA) supported the circular nature of the genome and direct sequencing of RCA products confirmed the HTS-derived sequence. An infectious clone was generated and used to induce systemic infection after agrobacterium-mediated inoculation of sugar beet, tomato and Nicotiana benthamiana, thereby demonstrating that the cloned genome is biologically active in taxonomically distinct hosts. The RNA-seq data revealed a novel splicing event in the complementary-sense transcripts which was confirmed by RT-PCR. Together, these results expand the known host range and geographic context of BCV1 and establish an experimental system for studying a capulavirus pathosystem.