Complete genomic sequence analyses of Turnip mosaic virus basal-BR isolates from China.

Isolates of Turnip mosaic virus (TuMV) are divided into four molecular lineages based on host range and geographical origins. Basal-BR is one of the four lineages and represented a new emergent lineage in East Asia. In one previous paper, we report the occurrence of basal-BR isolates in China. Here, we presented the first two complete genomic sequences of Chinese TuMV basal-BR isolates, WFLB06 and TANX2. The genomes of both isolates were 9833 nucleotides excluding the poly(A) tail, and had identical genomic structure. Most of their genes shared the highest identities with Japanese isolates. Recombination analysis showed that WFLB06 was an interlineage recombinant of basal-BR and Asian-BR parents, while TANX2 was an intralineage recombinant of basal-BR parents, and these two isolates represented two novel recombination patterns of TuMV. The ratio of nonsynonymous and synonymous substitution for the P1 gene of Chinese TuMV population was the highest and amounted to 12 times higher than that for the NIa-Pro gene, which implies that the selection pressure on the P1 gene was the highest among the genes present in the genome.