Evolutionary trajectory of turnip mosaic virus populations adapting to a new host.

Little is known about how some plant viruses establish successful cross-species transmission whilst others do not; the genetic basis for adaptation is largely unknown. This study investigated the genetic changes that occurred using the progeny of an infectious clone, p35Tunos, derived from the turnip mosaic virus (TuMV) UK 1 isolate, which has a Brassica host type, but rarely infects Raphanus systemically and then only asymptomatically. The genetic trajectory leading to viral adaptation was studied in a TuMV isolate passaged in Nicotiana benthamiana (parental), Brassica rapa, the old (susceptible) host and Raphanus sativus, the new (almost insusceptible) host.

Patterns of recombination in turnip mosaic virus genomic sequences indicate hotspots of recombination.

Potyviruses have variable single-stranded RNA genomes and many show clear evidence of recombination. This report studied the distribution of recombination sites in the genomes of 92 isolates of the potyvirus Turnip mosaic virus (TuMV); 42 came from the international gene sequence databases and an additional 50 complete genomic sequences were generated from field samples collected in Europe and Asia. The sequences were examined for evidence of recombination using seven different sequence comparison methods and the exact position of each site was confirmed by sequence composition analysis.