Genetic diversity among Banana streak virus isolates from Australia

Banana streak virus (BSV) is an important pathogen of bananas and plantains (Musa spp.) throughout the world. We have cloned and sequenced part of the genomes of four isolates of BSV from Australia, designated BSV-RD, BSV-Cav , BSV-Mys, and BSV-GF. These isolates originated from banana cvs. Red Dacca , Williams, Mysore, and Goldfinger, respectively. All clones contained a se quence covering part of open reading frame III and the intergenic region of the badnavirus genome. The sequences were compared with those of other bad naviruses, including BSV-Onne, a previously characterized isolate from Nige ria. The BSV-RD sequence was virtually identical to that of BSV-Onne, diffe ring by only two nucleotides over 1,292 bp. However, BSV-Cav, -Mys, and -GF were divergent in nucleotide sequence. Phylogenetic analyses using conserv ed sequences in the ribonuclease H domain revealed that all BSV isolates we re more closely related to each other than to any other badnavirus. BSV-Cav was most closely related to BSV-Onne, and there was 95.1% identity between the two amino acid sequences. Other relationships between the BSV isolates were less similar, with sequence identities ranging from 66.4 to 78.2%, wh ich is a magnitude comparable to the distance between some of the recognize d badnavirus species. Immunocapture-polymerase chain reaction assays have b een developed, allowing specific detection and differentiation of the four isolates of BSV.