Molecular characterisation of dicot-infecting mastreviruses from Australia.

Monocotyledonous and dicotyledonous plant infecting mastreviruses threaten various agricultural systems throughout Africa, Eurasia and Australasia. In Australia three distinct mastrevirus species are known to infect dicotyledonous hosts such as chickpea, bean and tobacco. Amongst 34 new "dicot-infecting" mastrevirus full genome sequences obtained from these hosts we discovered one new species, four new strains, and various variants of previously described mastrevirus species. Besides providing additional support for the hypothesis that evolutionary processes operating during dicot-infecting mastrevirus evolution (such as patterns of pervasive homologous and non-homologous recombination, and strong purifying selection acting on all genes) have mostly mirrored those found in their monocot-infecting counterparts, we find that the Australian dicot-infecting viruses display patterns of phylogeographic clustering reminiscent of those displayed by monocot infecting mastrevirus species such as Panicum streak virus and Maize streak virus.

Complete genome sequence of a novel badnavirus, banana streak IM virus.

In 1999, banana streak disease outbreaks occurred at two locations in Australia in new banana hybrids that were being screened for fusarium wilt resistance. Two different badnaviruses, banana streak GF virus and a newly discovered virus called banana streak IM virus (BSIMV), were detected in these plants. The complete nucleotide sequence of the BSIMV genome was determined and comprised 7768 nt. Three open reading frames were detected, the first beginning with a non-conventional start codon (CUG). A 55-nt repetition in the putative pregenomic RNA promoter was also identified. Phylogenetic analysis suggests that BSIMV is most closely related to banana streak VN virus.