Banana contains a diverse array of endogenous badnaviruses

Banana contains a diverse array of endogenous badnaviruses
Andrew D. W. Geering1, Neil E. Olszewski2, Glyn Harper3, Benham E. L. Lockhart4, Roger Hull3 and John E. Thomas1

1 Department of Primary Industries and Fisheries, 80 Meiers Road, Indooroopilly, Queensland 4068, Australia
2 Department of Plant Biology, University of Minnesota, St Paul, MN 55108, USA
3 John Innes Centre, Colney Lane, Norwich NR4 7UH, UK
4 Department of Plant Pathology, University of Minnesota, St Paul, MN 55108, USA


Correspondence
Andrew D. W. Geering
andrew.geering@dpi.qld.gov.au

Banana streak disease is caused by several distinct badnavirus species, one of which is Banana streak Obino l'Ewai virus. Banana streak Obino l'Ewai virus has severely hindered international banana (Musa spp.) breeding programmes, as new hybrids are frequently infected with this virus, curtailing any further exploitation. This infection is thought to arise from viral DNA integrated in the nuclear genome of Musa balbisiana (B genome), one of the wild species contributing to many of the banana cultivars currently grown. In order to determine whether the DNA of other badnavirus species is integrated in the Musa genome, PCR-amplified DNA fragments from Musa acuminata, M. balbisiana and Musa schizocarpa, as well as cultivars ‘Obino l'Ewai’ and ‘Klue Tiparot’, were cloned. In total, 103 clones were sequenced and all had similarity to open reading frame III in the badnavirus genome, although there was remarkable variation, with 36 distinct sequences being recognized with less than 85 % nucleotide identity to each other. There was no commonality in the sequences amplified from M. acuminata and M. balbisiana, suggesting that integration occurred following the separation of these species. Analysis of rates of non-synonymous and synonymous substitution suggested that the integrated sequences evolved under a high degree of selective constraint as might be expected for a living badnavirus, and that each distinct sequence resulted from an independent integration event.

The GenBank/EMBL/DDBJ accession numbers reported in this paper are AY189378–AY189383, AY189384–AY189392, AY189444–AY189453, AY189393–AY189400, AY189401–AY189419, AY189420–AY189435 and AY189436–AY189443