Characterization and genetic variability of coat protein genes of Apple chlorotic leaf spot virus isolates from southern Brazil.

Apple chlorotic leaf spot virus(ACLSV) infects temperate rosaceous fruit trees worldwide and causes a wide range of diseases that are economically highly damaging. This study was carried out to analyze genetic variability of regional ACLSV isolates and compare it with ACLSV isolates from other parts of the world. Nineteen amplicons of ACLSV, corresponding to the coat protein (CP) gene of isolates from apple, plum, and nectarine, from two states in southern Brazil, have been analyzed for genetic variation and compared phylogenetically among themselves and with other sequences available in GenBank. Sequences identities among complete CP genes of these isolates ranged from 87.5 to 100% and 92.2 to 100% at the nucleotide (nt) and the deduced amino acid (daa) levels, respectively. In the comparison with isolates from Asia, Europe and North America, identities were 68.4 to 100% and 72.5 to 100% at nt and daa levels, respectively. Phylogenetic trees based on nucleotide sequences showed that these isolates grouped into two clusters, cluster 1 containing apple isolates and cluster 2 comprising apple, plum and nec- tarine isolates. Most Brazilian isolates showed conserved signatures (Ser 40 ,Leu 59 ,Tyr 75 ,Thr 130 and Leu 184 )intheirCPs, which place them with type B6 isolates. However, some Brazilian isolates were found to be variants of type B6. These analyzes indicated that Brazilian isolates had lower genetic variability compared to isolates from China, India and Japan and that the CP genes were under negative selection. The greatest diversity of nucleotides was observed in the central portion of the CP gene, represented predominantly by synonymous substitutions. One natural recombinant was detected among ACLSV isolates from Brazil. Keywords ACLSV . Molecular characterization. Variability. Phylogeny. Recombination. Selection.https://doi.org/10.1007/s40858-017-0197-

Phylogenetic analysis of viruses in tuscan vitis vinifera sylvestris (Gmeli) hegi

The health status of the native grapevine Vitis vinifera subsp. sylvestris (Gmeli) Hegi in natural areas in Europe has received little attention. A survey was carried out on wild grapevines in Tuscany (Italy), where isolates of the Grapevine rupestris stem pitting virus (GRSPaV), Grapevine leafroll-associated virus 1 and 3 (GLRaV-1 and GLRaV-3) and Grapevine virus A (GVA) were detected. The complete coat protein (CP) region of these isolates was sequenced to investigate the relationship of the viral variants from Tuscan wild grapevines with isolates from different geographical origins. According to the phylogenetic analyses, GLRaV-1 and GLRaV-3 isolates from Tuscan wild grapevines clustered with isolates from cultivated grapevines with nucleotide sequence identities ranging from 66% to 87% and from 72.5% to 99% respectively, without any correlation between the distribution and geographical origin. Conversely, GRSPaV and GVA isolates clustered together with other Italian isolates from V. vinifera with nucleotide sequence identities ranging from 71.14% to 96.12% and from 73.5% to 92%, respectively. Our analysis of the whole amino acid sequences revealed a high conservation level for the studied proteins explained by a selective pressure on this genomic region, probably due to functional constraints imposed on CP, such as specific interactions with cellular receptors in the insect vectors necessary for successful transmission. In addition, analyses of genetic recombination suggest no significant point mutations that might play a significant role in genetic diversification. The dN/dS ratio also estimated a low number of non-silent mutations, highlighting the purifying selective pressure. The widespread distribution of the Rugose wood complex (GRSPaV and GVA associated disease) in comparison with the Grapevine Leafroll associated viruses (GLRaV-1 and -3) could explain the major geographical correlation found for the viral variants detected in Tuscany