Features of the strawberry field repository formation

For the successful functioning of a breeding and nursery center of scientific and practical work with fruit and small fruit crops, an important task is to create repositories, including thosein the field. A field repository is a plant gene bank based in accordance with international standards on planting material that is free from dangerous pathogens, including viruses, representing tested for productivity typical plants.For the purpose of a comparative study of promising varieties, hybrids and clones-candidates for original plants, a field repository and mother plantation of strawberries clones and varieties have been created on the territory of the Federal Horticultural Research Center for Breeding, Agrotechnology and Nursery.As a result of research in 2015-2020, 386 high-yielding strawberry plants were selected and tested for the main harmful viruses using diagnostic kits from “Loewe” firm (Germany). The prevalence of harmful Arabis mosaic virus (ArMV), Raspberry ringspot virus (RpRSV), Tomato black ring virus (TBRV), Strawberry latent ringspot virus (SLRSV), Cucumber mosaic virus (CMV) in strawberry plantations depended on the area cultivation, varietal composition of plantings and ranged from 31 to 69 %. The prevalence of viruses RpRSV (up to 36 %), TBRV (up to 31 %) and CMV (up to 22 %) was established. The high efficiency of dry-air thermotherapy for the recovery of strawberries with the number of virus-free intact plants of 56 % has been shown.A genebank of "candidates for original plants" has been formed from 234 strawberry plants of 39 varieties and hybrids, which, after confirming their status by PCR, will be transferred to the category of "original plants".

Preliminary Study of Viruses Infecting Strawberry (Fragaria spp.) in the Mid-Southern United States

Strawberry is an important economic crop in the mid-southern United States, however, limited information is known about the viruses present in strawberry fields in Arkansas, Missouri, Oklahoma, and Texas. The purpose of this study was to determine the presence of particular viruses infecting strawberry crops in the above four states. A total of 816 strawberry leaf samples were randomly collected from grower’s fields during the 2014 and 2016 growing seasons and tested by dot-immunobinding assay (DIBA) against antisera of eight available viruses: apple mosaic virus (ApMV), arabis mosaic virus (ArMV), raspberry bushy dwarf virus (RBDV), raspberry ringspot virus (RpRSV), strawberry mild yellow edge virus (SMYEV), tobacco necrosis virus (TNV), tomato black ring virus (TBRV), and tomato ringspot virus (ToRSV). Of the eight viruses, ApMV, RBDV, and SMYEV had the highest infection rates in 2014, while ApMV, ArMV, ToRSV and SMYEV were the most prevalent viruses in 2016. Mixed infection of more than one virus was very common in samples collected from all four states. Our preliminary results showed that the distribution of virus relative frequencies differed significantly among seven sample locations across the states within a sample year, but we could not show statistical differences among the years based on our sample sizes. Mixed infection in strawberries were higher than expected in 2014 and lower than expected in 2016 based on viruses being independent infections. Overall, the occurrence of the viruses in strawberry crops could have important potential impacts for strawberry production in the mid-southern states.

Metagenomic analysis of nepoviruses: diversity, evolution and identification of a genome region in members of subgroup A that appears to be important for host range

Data mining and metagenomic analysis of 277 open reading frame sequences of bipartite RNA viruses of the genus Nepovirus, family Secoviridae, were performed, documenting how challenging it can be to unequivocally assign a virus to a particular species, especially those in subgroups A and C, based on some of the currently adopted taxonomic demarcation criteria. This work suggests a possible need for their amendment to accommodate pangenome information. In addition, we revealed a host-dependent structure of arabis mosaic virus (ArMV) populations at a cladistic level and confirmed a phylogeographic structure of grapevine fanleaf virus (GFLV) populations. We also identified new putative recombination events in members of subgroups A, B and C. The evolutionary specificity of some capsid regions of ArMV and GFLV that were described previously and biologically validated as determinants of nematode transmission was circumscribed in silico. Furthermore, a C-terminal segment of the RNA-dependent RNA polymerase of members of subgroup A was predicted to be a putative host range determinant based on statistically supported higher π (substitutions per site) values for GFLV and ArMV isolates infecting Vitis spp. compared with non-Vitis-infecting ArMV isolates. This study illustrates how sequence information obtained via high-throughput sequencing can increase our understanding of mechanisms that modulate virus diversity and evolution and create new opportunities for advancing studies on the biology of economically important plant viruses.

Genetic Structure and Molecular Variability of Grapevine Fanleaf Virus in Sicily

Grapevine fanleaf virus (GFLV) is one of the main causes of grapevine fanleaf degeneration disease (GFDD) and is present in almost all areas where grapevine is cultivated. In this work, we ascertained the presence and spread of GFLV in different commercial vineyards in four Sicilian provinces (Italy), and its genetic structure and molecular variability were studied. In detail, a total of 617 grapevine samples of 11 autochthonous grapevine cultivars were collected in 20 commercial vineyards. Preliminary screening by serological (DAS-ELISA) and molecular (RT-PCR) analyses for ArMV (arabis mosaic virus) and GFLV detection were conducted. Results obtained showed the absence of ArMV in all the samples analyzed, while 48 out of 617 samples gave positive results to GFLV, for a total of 9 out of 11 cultivars analyzed. Phylogenetic analyses carried out on the GFLV-CP gene of 18 Sicilian GFLV sequences selected in this study showed a certain degree of variability among the Sicilian isolates, suggesting a different origin, probably as a consequence of the continuous interchange of GFLV-infected propagating material with other Italian regions or viticultural areas located in other countries.

Detection and phylogeny of viruses in native Albanian olive varieties

Forty samples representing 14 native Albanian and two foreign olive varieties were collected from an olive varietal collection plot in the Valias region (Tirana, Albania). The samples were assayed by RT-PCR for presence of olive-infecting viruses, including arabis mosaic virus (ArMV), cherry leaf roll virus (CLRV), cucumber mosaic virus (CMV), olive latent ringspot virus (OLRSV), olive latent virus 1 (OLV-1), olive leaf yellowing-associated virus (OLYaV), strawberry latent ringspot virus (SLRSV) and by PCR for the bacterium Xylella fastidiosa (Xf). Ninety-eight percent of the samples were infected with at least one virus. OLYaV was the most prevalent (85% of samples), followed by OLV-1 (50%), OLRSV (48%), CMV (28%), SLRSV (3%) and CLRV (5%), whereas ArMV and Xf were absent. Fifty-five percent of the samples were infected with one virus, 13% with two viruses, 20% with three, and 5% with four. Analyses of the nucleotide sequences of the Albanian virus isolates generally showed low genetic variability, and that most were phylogenetically related to Mediterranean isolates, in particular to those from Greece and Italy. Five olive trees, representing three native cultivars (‘Managiel’, ‘Kalinjot’ and ‘Kushan-Preze’) and one foreign (‘Leccino’), were found to be plants of the Conformitas Agraria Communitatis (“CAC”) category i.e. free of ArMV, CLRV, SLRSV and OLYaV. Only one tree of the native cultivar ‘Ulliri i kuq’ was free of all tested viruses, so this is plant material of the “Virus-tested” category. Olives derived from both categories could be used for propagation of standard quality plant materiel in a future certification programme for olive in Albania. This is the first report of CLRV, OLRSV, CMV and OLV-1 in Albania. The study also reveals the precarious health status of native olive varieties in the Valias varietal collection plot. However, the discovery of six plants representing two certifiable categories is a first step in a future olive tree certification program in the country.

Metagenomic Analyses of Nepoviruses: Diversity, Evolution and Identification of a Hitherto Undescribed Putative Region for Host Range in Subgroup a Species

Datamining and metagenomic analyses of 277 open reading frame sequences of bipartite RNA viruses and variants in the genus Nepovirus documented how delicate it can be to unequivocally identify species, in particular subgroup A and C species, based on some of the currently adopted taxonomic demarcation criteria. It suggests a possible need for their amendment to accommodate pangenome information. In addition, we revealed a host-dependent structure of arabis mosaic virus (ArMV) populations at a cladistic level and confirmed a phylogeographic structure of grapevine fanleaf virus (GFLV) populations. We also identified new putative recombinant events for species of subgroups A, B and C. The evolutionary specificity of some capsid regions of ArMV and GFLV that were previously described and biologically validated as vector determinant was circumscribed in silico. Furthermore, a C-terminal segment of the RNA-dependent RNA polymerase of subgroup A species was predicted as a putative host range determinant based on statistically supported higher π values for GFLV and ArMV isolates infecting Vitis spp. compared to non-Vitis infecting ArMV isolates. This study illustrated how sequence information obtained via high throughput sequencing can increase our understanding of mechanisms that modulate virus diversity and evolution and create new opportunities for advancing studies on the biology of economically important plant viruses.

Studies on the Occurrence of Viruses in Planting Material of Grapevines in Southwestern Germany

Viral diseases in viticulture lead to annual losses in the quantity and quality of grape production. Since no direct control measures are available in practice, preventive measures are taken to keep the vines healthy. These include, for example, the testing of propagation material for viruses such as Arabis mosaic virus (ArMV), Grapevine fanleaf virus (GFLV) or Grapevine leafroll-associated virus 1 (GLRaV-1) and 3 (GLRaV-3). As long-term investigations have shown, GLRaV-1 (2.1%) occurs most frequently in southwestern German wine-growing regions, whereas GLRaV-3 (<0.1%) is almost never found. However, tests conducted over 12 years indicate that there is no general decline in virus-infected planting material. Thus, it can be assumed that a spread of the viruses via corresponding vectors still takes place unhindered. Beyond the examinations regulated within the German Wine Growing Ordinance, one-time tests were carried out on Grapevine Pinot gris virus (GPGV). This analysis showed that GPGV was found in 17.2% of the samples.

Survey of five major grapevine viruses infecting Blatina and Žilavka cultivars in Bosnia and Herzegovina

The sanitary status of grapevines has not yet been considered sufficiently in vineyards throughout Bosnia and Herzegovina (BiH). An extensive survey of five major grapevine viruses in the country was carried out in 2019. A total of 630 samples from the two dominant autochthonous cultivars, named Žilavka and Blatina, were tested by DAS-ELISA for the presence of grapevine leafroll-associated viruses (GLRaV-1 and 3), grapevine fleck virus (GFkV), grapevine fanleaf virus (GFLV) and Arabis mosaic virus (ArMV). Eighty-eight % of the samples were positive for at least one virus, and all five viruses were detected, thought with different incidence, i.e. GLRaV-3 (84%), GFLV (43%), GLRaV-1 (14%), GFkV (10%) and ArMV (0.2%). The majority of infected plants (about 75%) were asymptomatic. Specific virus symptoms were observed in the remaining infected plants, together with the reported GLRaV vectors, Planococcus ficus and Parthenolecanium corni, while nematodes of the Xiphinema genus were not found in the GFLV- or ArMV-infected vineyards. The GLRaV-3 CP phylogenetic analyses showed 75–100% nucleotide identity between the BiH and reference isolates, and the BiH isolates clustered into the major group. The dNS/dS ratio indicated a negative selection of the virus population, and the lack of geographical structuring within the population was observed. In addition, putative GLRaV-3 recombinants with breakpoints in the 5’ of the CP gene were detected, while no recombinant strains were identified for the other four viruses. The obtained results indicate a deteriorated sanitary status of the cultivated grapevines, the prevalence and intraspecies genetic diversity of GLRaV-3 throughout the country. The establishment of certified grapevine material and adequate virus vector control is therefore of primary importance to prevent further spread of these viruses. This study presents the results of the first molecular characterisation of grapevine viruses in Bosnia and Herzegovina.

Effect of fungicide farmayod on agrotechnical and technological indicators of grapevine, on viral diseases and oidium

The paper presents the study on the effect of Farmayod’s GR (100 g/l of iodine) spraying on vineyards of Cabernet Sauvignon and Baklanovsky varieties on the degree of viral and oidium prevalence as well as on agrobiological and technological indicators. According to the aggregate agrobiological and technological indicators, the best results on Cabernet Sauvignon variety were obtained when the drug was used at a concentration of 0.06 %. On the Baklanovsky variety the best indicators were obtained at a drug concentration of 0.04%. Testing of plant samples for the presence of Grapevine fan leaf virus, Arabis mosaic virus and Oidium tuckeri showed that after two years of applying the drug, the prevalence of infected plants (P, %) with Grapevine fanleaf virus on the Cabernet Sauvignon cultivar varied from 0% (fungicide concentration 0.04 and 0.05 %) to 0.8 % (0.06 %) and 2.65 % (control). For Baklanovsky variety: Grapevine fanleaf virus - concentration 0.04 % - 1.8; 0.05 % - 0.4; 0.06 % - 2.0; control - 2.65 %. Arabis mosaic virus – 0; 0; 3.0; 12.1 %, respectively. Oidium tuckeri was 0 % in all variants with any drug concentrations. Control variant and later 80 % for 29.09.