Development of badnavirus infectious clones for research in taro and banana

Abstract

Badnaviruses are double-stranded DNA (dsDNA) pararetroviruses in the genus Badnavirus, family Caulimoviridae, with a genome length typically of 7 to 8 kbp. Most possess three open reading frames (ORFs) on the sense strand of the virus genome while some members also encode a fourth ORF. Replication of these viruses occurs via reverse transcription of a greater-than-genome length RNA that serves as a template both for the translation of viral proteins and for reverse transcription to replicate the genome. The dsDNA genome facilitates the relatively straightforward preparation of infectious clones in plasmid vectors, which can be agro-inoculated into host plants to reconstitute an infection. These infectious clones are useful tools for investigation of host range, symptomatology, host plant resistance and can be modified as vectors for virus-induced gene silencing. We have prepared infectious clones of three badnaviruses, including taro bacilliform virus, which infects taro (Colocasia spp.) and two banana (Musa spp.)-infecting species, namely banana streak MY virus and banana streak CA virus. The infectious clones showed high infectivity in their respective host plants. Symptoms of infection in banana varied, with some accessions showing a significant delay in the time to develop symptoms.