Harmful viruses on stone fruit crops and sanitation methods

Relevance. Viral diseases can significantly reduce the yield of stone fruit crops. More than 30 viruses have been characterized on stone fruits crops, among which the most harmful are Plum pox virus (PPV), Prunus dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Cherry leaf roll spot virus (CLRV), Apple chlorotic leaf spot virus (ACLSV). Viral diseases monitoring is essential for controlling the viruses prevalence and choosing a control strategy. In the absence of healthy plants of a certain variety, health improvement is carried out using laboratory methods, including thermotherapy. Sanitation methods need to be improved in relation to the culture characteristics and the virus type. Of considerable interest is the development of techniques that reduce the viruses concentration when growing stone fruit trees in the field.Methods. During 2016–2020 using the ELISA (“Loewe” diagnostic kits) diagnostics of viruses on varieties and clonal rootstocks of cherry, sweet cherry and plum (660 plants) was carried out in the conditions of the Moscow region. For plant health in 2019–2021 used thermotherapy for 3 months. To study the effect of Pharmayod (“Farmbiomed”) on viruses in open ground, 24 plum plants of 5 varieties were treated with this drug at a concentration of 0.3 ml/l.Results. The total prevalence of viruses on cherries varieties was 44%, sweet cherries — 40%, plums — 59%, on clonal rootstocks — 46, 55 and 56% respectively. The highest incidence of PNRSV and PDV viruses has been established. Cherry plants of 11 varieties, free from the main harmful viruses, 4 varieties of sweet cherries, 12 varieties of plums and 9 forms of clonal rootstocks were revealed. The use of the Pharmayod on plum trees in the open field contributed to a decrease in the infection index of the studied viruses. Plum plants in a heat chamber were characterized by a higher survival rate and growth parameters in comparison with cherry and sweet cherry. After the completion of thermotherapy, a significant decrease in the index of infection in plants was noted.

Potato infection with viruses in the Republic of Bashkortostan and ribonuclease activity in tubers

The paper presents the results of enzyme immunoassay (ELISA) of the presence of potato viruses S (PVS), M (PVM), Y (PVY), X (PVX), and Potato Leaf Roll Virus (PLRV) in tubers of various potato varieties grown in 2019 in the Republic of Bashkortostan. PVS, PVM, PVY, PVX were detected, the VSLK virus was not detected. The greatest infection with PVS, PVM, and PVX was observed in samples of tubers of early-maturing varieties. Tubers of mid-early and late-maturing varieties were more often affected by PVY than early-maturing ones, and PVX was not detected in plants of those varieties. Ribonuclease (RNase) activity in potato tubers of 14 varieties depended on the earliness of the variety, regardless of the soil and climatic conditions. A statistically significant positive correlation (P<0.05) was found between the abundance of PVS and PVM viruses and RNase activity in tubers of medium-early and late-maturing varieties, whereas, on the contrary, a negative correlation between PVM and RNase activity was revealed when analyzing tubers of early-maturing varieties. It is concluded that the prevalence of potato viruses in the territory of the Republic of Bashkortostan and the activity of RNase in tuber seedlings depend on the potato variety and the type of viruses.

Establishment of Tissue Culture System of Actinidia deliciosa Cultivar “Guichang”

In order to breed virus-free plantlets of the kiwifruit cultivar “Guichang,” which belongs to Actinidia deliciosa, in this study, stem segments with buds were used as explants, the establishment of a tissue culture rapid propagation system was carried out, and then the virus status of tissue culture plantlets was detected via the real-time reverse transcription-polymerase chain reaction (RT-qPCR) method. The tissue culture rapid propagation system proved that the contamination and browning rates could be controlled below 20% and the survival rate could be exceeded by 70% when the single bud stem segment of “Guichang” kiwifruit was sterilized with 70% alcohol for 30–60 s and 15% NaClO for 15 min, respectively. Meanwhile, we screened the hormone concentration to get better results, and the appropriate medium for adventitious bud induction was MS + 6-BA (1.0 mg/L) + IBA (0.2 mg/L); for proliferation, it was MS + 6-BA (1.0 mg/L) + IBA (0.1 mg/L); and for rooting, it was 1/2 MS + IBA (0.3 mg/L), and the efficiency of induction, proliferation, and rooting could reach 74.07%, 79.63%, and 85.18%, respectively. In addition, the RT-qPCR results demonstrated that the infection rate of 9 viruses: apple stem grooving virus (ASGV), cucumber mosaic virus (CMV), Actinidia virus X (AVX), cucumber necrosis virus (CNV), ribgrass mosaic virus (RMV), citrus leaf blotch virus (CLBV), Actinidia virus B (AcVB), Pelargonium zonate spot virus (PZSV), and cherry leaf roll virus (CLRV) in the “Guichang” kiwifruit tissue culture plantlets was 0. This study could lay a foundation for the production of “Guichang” kiwifruit tissue culture seedlings, and the medium formula provided in this study was useful for the industrial rapid propagation of “Guichang” plantlets.

Coinfection of Cotton Plants with Watermelon Mosaic Virus and a Novel Polerovirus in China

Cotton is the most important fiber crop worldwide. To determine the presence of viruses in cotton plants showing leaf roll and vein yellowing symptoms in Henan Province of China, a small RNA-based deep sequencing approach was performed. Analysis of the de novo-assembled contigs followed by reverse transcription PCR allowed the reconstruction of watermelon mosaic virus and an unknown virus. The genome of the unknown virus was determined to be 5870 nucleotides in length, and has a genomic organization with characteristic features of previously reported poleroviruses. Sequence analysis revealed that the virus was closely related to, but significantly different from, cotton leafroll dwarf virus, a polerovirus of the family Solemoviridae. This virus had less than 90% amino acid sequence identity in the products of both ORF0 and ORF1. According to the polerovirus species demarcation criteria set by the International Committee on Taxonomy of Viruses, this virus should be assigned to a new polerovirus species, for which we propose the name “cotton leaf roll virus”.

Virus Incidence Associated with Native Potato Yield in Microcenters of Potato Genetic Diversity of Bolivian

In the Bolivian Andean region, a diversity native potatoes species (Solanum spp) are cultivated. Areas where many types of native potato are grown are known as microcentres of potato genetic diversity. However, yields are low in these places, apparently related to viral infections. The incidence of the potato-affecting viruses Potato Virus X (PVX), Potato Virus Y (PVY), Potato Leaf Roll Virus (PLRV), Andean Potato Latent Virus (APLV) and Andean Potato Mottle Virus (APMoV) was examined by DAS-ELISA in microcentres of two high Andean regions of Bolivia, i.e. an Aymara culture region in the north of La Paz, and a Quechua culture region in the Dept. of Cochabamba. The relationship between viral incidence and potato yield was explored as well. The presence of all five viruses was detected in both regions, except APMoV in the Aymara region. The mean overall incidence of viral infection was greater in the Aymara than in the Quechua region. The most commonly detected viruses were PVX, PVY and APLV. Mix-infections of PVY + PVX and PVY + PLRV were most common in the Aymara region, and PVX + APLV and PVX + APMoV in the Quechua region. Potato yield was less in Aymara than in Quechua region and it was correlated to higher incidence of PVY and PVX in Aymara region. Low yields and high incidence of viral infection seems to be related to the ancestral management by planting native seed potatoes of poor quality. In conclusion, four of the five viruses sought were detected in the Aymara region, and all five in the Quechua region, although the overall incidence of viral infection was greater in the Aymara region, where the yields recorded were also lower.Resumen.En la región andina boliviana se cultivan una diversidad de especies nativas de papa (Solanum spp). Las áreas donde se cultivan muchos tipos de papa nativa se conocen como microcentros de diversidad genética de la papa. Sin embargo, los rendimientos son bajos en estos lugares, aparentemente relacionados con infecciones virales. Se examinó la incidencia de los virus que afectan a la papa, el Virus X de la Papa (PVX), Virus Y de la Papa (PVY), Virus del Rollo de hoja de Papa (PLRV), Virus Latente de la Papa Andina (APLV) y Virus moteado de la Papa Andina(APMoV) por DAS-ELISA en microcentros de dos regiones altoandinas de Bolivia, por ejemplo, una región de cultivo Aymara en el norte de La Paz y una región de cultivo Quechua en el Departamento de Cochabamba. También se exploró la relación entre la incidencia viral y el rendimiento de la papa. Se detectó la presencia de los cinco virus en ambas regiones, excepto APMoV en la región Aymara. La incidencia global media de infección viral fue mayor en la región Aymara que en la región Quechua. Los virus más comúnmente detectados fueron PVX, PVY y APLV. Las infecciones por mezcla de PVY + PVX y PVY + PLRV fueron más comunes en la región Aymara, y PVX + APLV y PVX + APMoV en la región Quechua. El rendimiento de papa fue menor enAaymara que en la región Quechua y se correlacionó con una mayor incidencia de PVY y PVX en la región Aymara. Estamos evidenciando que los bajos rendimientos y la alta incidencia de infección viral parecen estar relacionados con el manejo ancestral mediante la siembra de papas de semilla nativa de mala calidad. En conclusión, cuatro de los cinco virus buscados se detectaron en la región Aymara, y los cinco en la región Quechua, aunque la incidencia general de infección viral fue mayor en la región Aymara, donde los rendimientos registrados también fueron menores.

Nanobiotechnological Approaches to Enhance Potato Resistance against Potato Leafroll Virus (PLRV) Using Glycyrrhizic Acid Ammonium Salt and Salicylic Acid Nanoparticles

The present research was aiming to study In-Silico the effect of Glycyrrhizic Acid ammonium salt (GAS) and Salicylic acid (SA) on the coat protein of potato leafroll virus (PLRV). In addition, in-vitro studying the effect of (GAS NPs) and Salicylic acid (SA NPs) nanoparticles at concentrations 0.15, 0.30, 1.25 and 2.5 mM, respectively, to control, decline or reduce the presence of PLRV in potato plants Solanum tuberosum L. selena. (GAS NPs) and (SA NPs) were applied in the MS medium at concentrations 0.15, 0.30, 1.25 and 2.5 mM, respectively. Results revealed that, enhancement or decline the PLRV according to the initiation of specific pathways. The expression level of Kinase 3 gene increased significantly due to the two used concentrations of GAS NPs. While the expression of callose gene was upregulated significantly in response to treatment of PLRV infected plant with (GAS NPs) with concentration (0.30 mM). Treatment with (SA NPs) caused upregulation significance only of callose gene at (2.5 mM) concentration. The molecular modeling results of used compounds (glycyrrhizic acid ammonium salt and salicylic acid) showed highest score of binding and the best rms define value with a very good binding mode and perfect interactions with amino acids of the three subunits (A, B and C) forming the protein coat of leaf roll virus. Glycyrrhizic acid ammonium salt and salicylic acid nanoparticles could be perfect solution to produce potato plant free virus in-vitro. Further larger studies are needed to investigate the role of the studied compounds in vivo.

Knockdown of a novel ATPase domain of capsid protein inhibits genome packaging in potato leaf roll virus

Potato leaf roll virus (PLRV) uses powerful molecular machines to package its genome into a viral capsid employing ATP as fuel. Although, recent bioinformatics and structural studies have revealed detailed mechanism of DNA packaging, little is known about the mechanochemistry of genome packaging in small plant viruses such as PLRV. We have identified a novel P-loop-containing ATPase domain with two Walker A-like motifs, two arginine fingers, and two sensor motifs distributed throughout the polypeptide chain of PLRV capsid protein (CP). The composition and arrangement of the ATP binding and hydrolysis domain of PLRV CP is unique and rarely reported. The discovery of the system sheds new light on the mechanism of viral genome packaging, regulation of viral assembly process, and evolution of plant viruses. Here, we used the RNAi approach to suppress CP gene expression, which in turn prevented PLRV genome packaging and assembly in Solanum tuberosum cv. Khufri Ashoka. Potato plants agroinfiltrated with siRNA constructs against the ATPase domain of CP exhibited no rolling symptoms upon PLRV infection, indicating that the silencing of CP gene expression is an efficient method for generating PLRV-resistant potato plants. Moreover, our findings provide a robust approach to generate PLRV-resistant potato plants, which can be further extended to other species. Finally, we propose a new mechanism of genome packaging and assembly in plant viruses.

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.