Wilmer Perez

Complete genome sequences of new divergent potato virus X isolates and discrimination between strains in a mixed infection using small RNAs sequencing approach

Potato virus X (PVX; genus Potexvirus, family Alphaflexiviridae, order Tymovirales) is one of the most widespread and intensively studied viruses of potato. However, little is known about its diversity in its likely center of radiation, the Andean region of South America. To fill this gap, the strategy of Illumina deep sequencing of small RNAs was used to obtain complete or near complete genome sequence of PVX from 5 symptomatically infected greenhouse and 3 field samples (Solanum tuberosum) from Peru. PVX sequences determined in this study were assigned into three different phylogenetic groups of isolates. Notably, a complete genome sequence of a representative of a new PVX phylogenetic lineage was obtained, which shows a high level of sequence dissimilarity to other completely sequenced isolates (∼17%). The new PVX genotype was detected in greenhouse and field samples. One of the field samples was infected with the mixture of two PVX strains, which were efficiently discriminated using small RNA sequencing approach. The study confirms the utility of small RNAs deep sequencing for successful viral strain differentiation and discovery of new viral strains and indicates a high diversity of PVX in the Andean region of South America, a pattern which may be expected also for other potato pathogens.

Complete sequence and variability of a new subgroup B nepovirus infecting potato in central Peru

The complete bipartite genome (RNA1 and RNA2) of a new nepovirus infecting potato was obtained using small RNA sequencing and assembly complemented by Sanger sequencing. Each RNA encodes a single polyprotein, flanked by 5’ and 3’ untranslate regions (UTR) and followed by a poly (A) tail. The putative polyproteins encoded by RNA1 and RNA2 had sets of motifs which are characteristic of viruses in the genus Nepovirus. Sequence comparisons using the Pro-Pol region and the coat protein, including phylogenetic analysis of these regions, showed closest relationships with nepoviruses. The data obtained support the taxonomical status of this new virus (putative named Potato virus B, PVB) as a member of the genus Nepovirus, subgroup B.