Yellow Virus Research Articles

Control of Sweetpotato Whitefly Adults with Foliar Neonicotinoid Insecticides in Spring Cantaloupes, 2014

With the loss of the endosulfan on melons, this trial was designed to evaluate the efficacy of several neonicotinoid alternatives against adult sweetpotato whiteflies and the associated incidence of cucurbit yellow stunting disorder virus (CYSDV) in spring melons. Cantaloupe plots planted with ‘Sol Dorado’ were established at the Yuma Agricultural Center on 20 March, 2014, and managed similarly to local growing practices. Plots consisted of a 84-inch bed, 45-ft-long with a 7-ft buffer between each plot. The study was designed as a randomized complete block design with four replicates per treatment. Product formulations and rates are shown in Tables 1 and 2. Three foliar spray applications were applied on 29 April …

LEEK YELLOW STRIPE VIRUS ISOLATES FROM BRAZIL FORM A DISTINCT CLADE BASED ON THE P1 GENE

The complete genome sequence of a garlic isolate of Leek yellow stripe virus (LYSV) from Brazil (LYSV-MG) was determined and its phylogenetic relationships with other LYSV isolates from other parts of the world were inferred. The LYSV-MG genome consists of 10,341 nucleotides and encodes a polyprotein of 3,221 amino acids. Brazilian LYSV isolates are more closely related to S-type than to N-type isolates but do not have a deletion in the P1 gene. Partial nucleotide sequence analysis of the P1 gene revealed 97-99% identity among Brazilian isolates, and 51-64% identity between Brazilian isolates and isolates from other countries for which sequence information is available in Genbank. The Brazilian isolates formed a monophyletic group closest to the S-type isolates and one isolate from Okinawa (O-type). These data suggest that Brazilian LYSV isolates are derived from an ancestral source of the Okinawa and S-type isolates, prior to the occurrence of the P1 deletion and divergence of the S-type isolates.

Control of Sweetpotato Whitefly With Foliar Insecticides on Staked Tomatoes, Fall 2013

SWF biotype B continues to be a destructive tomato pest in Florida, mostly due to its role as a vector of tomato yellow leaf curl virus. Affected plants yield little or no fruit when infected young. For this trial, two sets of three beds 420 ft in length were prepared on 15 Aug at the Southwest Florida Research and Education Center in Immokalee, FL. Dry fertilizer (10-2-10 NPK) was incorporated at a rate of 1,000 lb/acre, beds were fumigated with PicClor 60 EC at 240 lbs/acre, and each bed received two drip tapes with 8-inch emitter spacing and was covered with black polyethylene film mulch. Seedlings of ‘Soraya’ obtained from a commercial greenhouse were transplanted 18 inches apart on 6 Sep. Fertilizer was injected during the course of the growing season as liquid 7-2-7 through the drip, and Actigard (0.33–0.50 oz/acre), …

FIRST REPORT OF TOMATO YELLOW LEAF CURL CHINAVIRUS INFECTING MALVA ROTUNDIFOLIA IN CHINA

Malva rotundifolia L. is a common medicinal herb in China. In 2010, samples of 10 symptomatic Malva parviflora L. plants showing yellow vein and leaf crinkling, and of two symptomless plants were collected in Sichuan (China). A 500 bp DNA fragment was successfully amplified from the 10 symptomatic samples with the degenerate primers PA/PB specific to begomoviruses (family Geminiviridae) (Deng et al., 1994). The fragment of isolate SC226 was randomly selected for cloning and sequencing (GenBank accession No. KP293739). Based on the sequence obtained, the specific primers Y6F1 (5’-ACCGGATGTACAGAAGCCCTGA-3’) and Y6R (5’-CTTCCGATACATGGGCCTGTTTG-3’) were designed to amplify the remaining DNA-A sequence. Sequence analysis showed that the full-length sequence of SC226 was 2738 nt long (JX679252) with the highest nucleotide sequence identity with isolate Y25 of Tomato yellow leaf curl China virus (TYLCCNV-[China:Yunnan 25:2002] (AJ457985)). Then, a 1200 nt long fragment specific to TYLCCNV was amplified from all symptomatic samples using primers Y10F1 and Y35+10R (Qing and Zhou, 2009). With the universal abutting primers (Briddon et al., 2002) for betasatellite DNA, an amplicon of 1300 bp was obtained from 10 symptomatic samples. Sequence comparison showed that the betasatellite is 1335 bp long (JX679253) and has a 85.8% identity with Tomato yellow leaf curl China betasatellite (TYLCCNB-[China:Yunnan 149:2009] (GU058280)). An approximate 900 bp amplicon specific to TYLCCNB was detectable in all symptomatic samples using the primers Y10β/β02 (Qing and Zhou, 2009). Neither TYLCCNV nor TYLCCNB was detectable in symptomless samples. This is the first report of TYLCCNV associated with its betasatellite infecting Malva rotundifolia.

Lack of evidence for seed transmission of Citrus yellow vein clearing virus despite its frequent detection in seed tissues.

Citrus yellow vein clearing virus (CYVCV), the putative causal agent of yellow vein clearing disease of citrus, is transmissible by grafting and is spread by aphids. However, whether CYVCV is seed-transmitted is not well documented. In this study, seed transmission of CYVCV was investigated in Daidai, Carrizo citrange and Rough lemon. CYVCV was detected in the endotesta, cotyledons and embryonic axis of seeds collected from the fruits of CYVCV-infected plants by qRT-PCR. Furthermore, the relative expression values of CYVCV were significantly higher in infected leaves than in the cotyledons or embryonic axis of seeds. Although viral RNA was found in few samples of radicles of germinating seed, none of the seedlings showed any symptoms for one year and were RT-PCR negative for CYVCV. The present study indicated that CYVCV could be localized in the seed tissues, but was not transmitted to the progeny. Absence of seed transmission may be consequent to the low CYVCV titre in embryo tissue.

Absolute quantification of dengue virus serotype 4 chimera vaccine candidate in Vero cell culture by targeted mass spectrometry.

Infection by dengue flavivirus is transmitted by mosquitoes and affects tens to hundreds of millions people around the world each year. Four serotypes have been described, all of which cause similar disease. Currently, there no approved vaccines or specific therapeutics for dengue, although several vaccine prototypes are in different stages of clinical development. Among them, a chimeric vaccine, built from the replication machinery of the yellow fever 17D virus, has shown promising results in phase III trials. Accurate quantitation of expressed viral particles in alive attenuated viral antigen vaccine is essential and determination of infectious titer is usually the method of choice. The current paper describes an alternative or orthogonal strategy, namely, a multiplexed and absolute assay of four proteins of the chimera yellow fever/dengue serotype 4 virus using targeted MS in SRM mode. Over 1 month, variability of the assay using a partially purified Vero cell extract was between 8 and 17%, and accuracy was between 80 and 120%. In addition, the assay was linear between 6.25 and 200 nmol/L and could therefore be used in the near future to quantify dengue virus type 4 during production and purification from Vero cells.

Determinants of Disease Phenotype Differences Caused by Closely-Related Isolates of Begomovirus Betasatellites Inoculated with the Same Species of Helper Virus.

Tomato yellow leaf curl China virus (TYLCCNV) is a monopartite begomovirus associated with different betasatellites. In this study, we investigate two different isolates of Tomato yellow leaf curl China betasatellite (TYLCCNB) to determine what features of the viral genome are required for induction of characteristic phenotypic differences between closely-related betasatellite. When co-agroinoculated with TYLCCNV into Nicotiana spp. and tomato plants, TYLCCNB-Y25 induced only leaf curling on all hosts, while TYLCCNB-Y10 also induced enations, vein yellowing, and shoot distortions. Further assays showed that βC1 of TYLCCNB-Y25 differs from that of TYLCCNB-Y10 in symptom induction and transcriptional modulating. Hybrid satellites were constructed in which the βC1 gene or 200 nt partial promoter-like fragment upstream of the βC1 were exchanged. Infectivity assays showed that a TYLCCNB-Y25 hybrid with the intact TYLCCNB-Y10 βC1 gene was able to induce vein yellowing, shoot distortions, and a reduced size and number of enations. A TYLCCNB-Y10 hybrid with the intact TYLCCNB-Y25 βC1 gene produced only leaf curling. In contrast, the TYLCCNB-Y25 and TYLCCNB-Y10 hybrids with swapped partial promoter-like regions had little effect on the phenotypes induced by wild-type betasatellites. Further experiments showed that the TYLCCNB-Y25 hybrid carrying the C-terminal region of TYLCCNB-Y10 βC1 induced TYLCCNB-Y10-like symptoms. These findings indicate that the βC1 protein is the major symptom determinant and that the C-terminal region of βC1 plays an important role in symptom induction.

Resistance to viral yellow leaf curl in tomato through RNAi targeting two Begomovirus species strains

Tomato yellow leaf curl disease caused by different begomovirus species leads to substantial tomato production losses worldwide. In Taiwan, the monopartite tomato leaf curl Taiwan virus (ToLCTWV) and bi-partite tomato yellow leaf curl Thailand virus (TYLCTHV) are the predominant begomovirus species causing this disease. Resistance genes are available in wild tomato species and a continuous search for new resistance genes and alternative control methods is required to respond to the rapid evolution of virus strains. RNA interference is an efficient technology to induce resistance against viral pathogens. Six different sections of the ToLCTWV genome were tested in transformed tomato for their capacity to reduce symptoms and inhibit viral DNA accumulation. The two most effective constructs for ToLCTWV infection carried regions of the C1 and C2 genes, and portions of either the C3 or C4 gene of ToLCTWV. A RNAi construct containing fusions of C1, C2 and C3 sections of ToLCTWV and the corresponding sections of the TYLCTHV DNA-A genome were introgressed into tomato line CLN1621L. R1 and R2 families were challenged using viruliferous whiteflies in separate screen houses for ToLCTWV and TYLCTHV. Sixteen and 12 R2 plants derived from one primary transformant remained symptomless until at least 3 weeks after exposure to ToLCTWV and TYLCTHV, respectively, and accumulated only very low titres of viral DNA, as shown by real-time polymerase chain reaction analysis. Our results suggest that expression of bi-viral RNAi constructs in tomato can lead to resistance against two different tomato infecting begomovirus species.

Do Secondary Bacterial Endosymbionts of Aphids Affect the Vector Specificity or Transmission Efficiency of Plant Viruses?

Several vectoring insects, such as aphids and white fly, harbour secondary bacterial endosymbionts. When an insect vectors a persistently transmitted plant virus, this virus should pass through the insect gut into the haemolymph. The secondary bacteria, however, may affect the movement, persistence and replication of the viruses, thereby influencing the vectoring efficacy or specificity of the insect in respect to these plant viruses. This issue, however, has not yet been fully investigated. Hence, the aim of this primary study is to investigate the effect of secondary bacterial endosymbionts of Sitobion avenae clones in respect of the vector specificity and transmission efficiency of barley yellow dwarf virus, as well as to highlight in general the role of secondary bacteria in virus transmission. The experiments were performed according to standard protocols using one virus strain, BYDV-PAV, and four S. avenae clones harbouring different bacterial and genetic profiles. We found that all tested clones we...

First Report of Canna yellow mottle virus Associated With Yellow Vein Mosaic Disease of Betel Vine (Piper betel) in India

First Report of <i>Canna yellow mottle virus</i> Associated With Yellow Vein Mosaic Disease of Betel Vine (<i>Piper betel</i>) in India

Molecular characterization of a Strawberry mild yellow edge virus isolate from Canada

Over the past several years, strawberry production in Canada and the United States has been severely affected by strawberry acute decline symptoms. The decline disease is apparently caused by synergistic infections of several viruses, including Strawberry mild yellow edge virus (SMYEV) and Strawberry mottle virus (SMoV). To better understand the causal viral pathogens, we cloned and sequenced the entire genome of a SMYEV isolate, AB5-2, from a strawberry field in Prince Edward Island. The viral genome of AB5-2 consists of 5969 nucleotides excluding the 3ʹ terminal poly(A) tail. Searches of the NCBI database identified two SMYEV isolates (MY-18 from the USA and D74 from Germany) whose complete genome sequences were documented and 28 SMYEV isolates with determined coat protein (CP) sequences. At the genome level, the Canadian SMYEV isolate shares 86% and 90% nucleotide sequence identities to MY-18 and D74, respectively. Phylogenetic analysis of all CP sequences available clustered 28 SMYEV isolates into five phylogroups, including AB5-2 alone as a new group, suggesting this Canadian isolate is distinct from SMYEV isolates of other origins. This report represents the first molecular characterization of a SMYEV isolate from Canada.

Incidence of barley yellow dwarf virus (BYDV) in wheat (Triticum spp) in the southern region of Paraguay

El virus de enanismo amarillo de la cebada (Barley yellow dwarf virus – BYDV) es un virus ampliamente distribuido en el mundo afectando a diversas Poaceas siendo transmitido por diferentes especies de afidos. Se realizaron controles por Test de Elisa mediante muestreos durante los periodos agricolas 2013 y 2014 para determinar los serotipos predominantes en los cultivos de trigo en la region sur del Paraguay que incluyeron los distritos: Fram, Obligado, Bella Vista y Capitan Miranda, igualmente durante el periodo agricola 2014 se instalaron trampas tipo Moericke a fin de identificar y cuantificar las poblaciones de afidos presentes durante el desarrollo del cultivo. Los resultados demostraron una amplia distribucion del BYDV-PAV en las muestras analizadas; se obtuvo solo un caso positivo para el BYDV-MAV; el CYDV-RPV no fue detectado. Los muestreos realizados de la poblacion de afidos demostraron que la especie mas abundante fue Rhopalosiphum padi L., demostrando su alta eficiencia en la transmision del serotipo PAV.

Farmers’ rice knowledge and adoption of new cultivars in the Tillabéry region of western Niger

Tillabery is the main rice growing region of Niger, and it includes both irrigated and lowland rice. Rice production has stagnated due to several factors this research investigated through farmers’ eyes. Semi-structured group discussions were carried out in 14 villages in which 153 farmers, after giving their informed consent, were individually subjected to a questionnaire, and farmers’ fields and storage facilities were visited. Fields were larger in private irrigation and lowland agrosystems compared to those in public irrigation schemes. The local farmers’ union was the only formal seed dissemination system. Farmers exchanged seed as well as did re-seeding of leftovers from the previous harvest. They indicated Rice yellow mottle virus (RYMV) and bacterial leaf blight (BLB) as the most prevalent biotic stresses in the irrigated agrosystems, but the RYMV-susceptible cultivars IR1529 and ‘Waihidjo’ are still the most popular varieties. Floods, birds, and hippopotamuses were the most damaging agents in lowland agrosystems where the landrace ‘Degaulle’/D5237 was the preferred cultivar. Rice farmers in the region of Tillabery were aware of the RYMV, could provide good descriptions of its symptoms, but could not establish the real causes of the disease nor its relationship with insects’ prevalence and other cultural practices. However, traditional management strategies were implemented to reduce RYMV epidemics. This situation showed that farmers in the region of Tillabery were willing to face RYMV epidemic outbreaks while growing their preferred rice cultivars. Good seed availability and absence of seed policy at the time of this study were also detected as bottlenecks in rice production increase in Tillabery.

A begomovirus associated with yellow vein symptoms of Oxalis debilis

‘Gold Veined Oxalis’ (Oxalis debilis) is an ornamental plant cultivar with attractive yellow vein foliage. After grafting scions of this plant to O. debilis plants that lacked the yellow vein foliage, grafted plants developed yellow vein suggesting that an infectious agent was the cause of the yellow vein. DNA extracts from O. debilis plants showing yellow vein were used in rolling circle amplification and PCR experiments. Sequence analyses of amplified DNA products suggested that a begomovirus was the cause of the yellow vein symptoms. The same begomovirus was found in the original sample and in graft inoculated plants that developed the yellow vein symptoms. The DNA A of the putative begomovirus, designated Oxalis yellow vein virus (OxYVV), shared 87 % overall nucleotide identities with the corresponding genome segments of Sida mottle virus, 85 % with Okra mottle virus, and 83 % with Tomato yellow spot virus. OxYVV virus was transmitted by the whitefly Bemisia tabaci Middle East-Asia Minor 1. This is another example of a virus that enhances the aesthetics of an ornamental plant.

Sequence analysis of Indian iris yellow spot virus ambisense genome segments: evidence of interspecies RNA recombination.

The nucleotide sequence of M- and S-RNA segments of an Indian iris yellow spot virus (IYSV) were determined. Sequence comparisons showed that both of these sequences shared less than 95% identity with those other known IYSV isolates. Phylogenetic analysis revealed that the S- and M-RNA sequences of known IYSV isolates clustered with those of the tospoviruses, tomato yellow ring virus, polygonum ringspot virus and hippeastrum chlorotic ringspot virus. Further, multiple recombination detection methods detected inter- and intra-species recombination events that clustered primarily within the intergenic regions of S- and M-RNA, suggesting that these are possibly recombination hotspots in IYSV and closely related tospoviruses.

Interactions Between Rice yellow mottle virus (RYMV) Isolates and Rice Germplasm from Niger

Rice yellow mottle virus (RYMV) is the most damaging virus in Niger’s rice agrosystems. We analysed host plant-RMYV interactions using 175 accession from the rice germplasm collection of Niger and 52 accessions from Mali. Five different virus isolates from Niger (three), Benin (one) and Burkina Faso (one) were used for inoculation. The assessment was based on visual disease symptom scoring, and secondary disease-related traits such as leaf chlorophyll content and plant height. Most rice accessions were susceptible to RMYV but a few African rice accessions displayed a level of resistance to some virus isolates, which was similar to that of the highly resistant TOG5681. Their host plant resistance was characterised by the absence of symptoms, low chlorosis and limited plant height reduction. Examining alleles using primers derived from the RYMV1 resistance gene revealed that one of these accessions has the rymv1-3 allele and other two accessions bear the rymv1-4 allele. We could not identify any known allele in one highly resistant accession, suggesting the presence of another resistance gene. The RYMV isolate BF1 from Burkina Faso was more aggressive than the three isolates from Niger, which were in turn found to be more aggressive than the isolate from Benin.

Rottboellia yellow mottle virus is a distinct species within the genus Sobemovirus.

Once considered a tentative member of the genus Sobemovirus, rottboellia yellow mottle virus (RoMoV) was excluded from the latest species list of the ICTV after the discovery of imperata yellow mottle virus (IYMV), which resembles RoMoV in host range and geographic origin. Here, sequence analysis of the complete genome of RoMoV suggested that it should be considered a distinct species within the genus Sobemovirus. It has the highest sequence identity (55 %) to ryegrass mottle virus (RGMoV), whereas its sequence identity to IYMV is lower (44 %). In a phylogenetic tree, RoMoV clusters together with RGMoV and artemisia virus A (ArtVA), a dicot-infecting sobemovirus.

Population dynamics of iris yellow spot virus in onion fields and lisianthus greenhouses in Japan

Iris yellow spot virus (IYSV, genus Tospovirus) mainly occurs on onion and lisianthus plants (Eustoma grandiflorum) in Japan. The virus is genetically diverse and is classified based on its nucleocapsid protein sequence into two genotypes, IYSVNL (NL) and IYSVBR (BR), first isolated in the Netherlands and Brazil, respectively. Both genotypes are present in Japan, and they are sometimes found in the same field. Furthermore, the two genotypes are occasionally detected in a single necrotic lesion of an infected plant (designated as a ‘mosaic’ genotype). In this study, the population structures of these two genotypes and their dynamics in onion fields and lisianthus greenhouses from 2004 to 2006 were analysed using reverse transcription-PCR-restriction length polymorphism analysis (RT-PCR-RFLP). In onion fields the two genotypes were detected in all three years, and the BR genotype predominated within a year. On the other hand, both genotypes were detected at the first outbreak each year in almost all lisianthus greenhouses; however, the BR genotype was more widespread than the NL genotype. These results suggest that the incidence of IYSV disease in lisianthus during each year was triggered by the invasion of viruliferous Thrips tabaci that have acquired one or both genotypes from nearby onion fields. Although the BR genotype predominated in the last stages of cultivation, IYSV disease might be expanded by monocyclic patterns but may occasionally spread secondarily in lisianthus greenhouses.

First report of Pepo aphid‐borne yellows virus on zucchini in Cote d'Ivoire

Cucurbits are very important crops for West African farmers, in particular in Cote d'Ivoire, ensuring self-sufficiency and the generation of income. However, plant viral diseases are a major constraint to cucurbit production (Lecoq &…

Production of virus-free garlic (Allium sativum L.) through meristem tip culture after solar or hot air treatment of cloves

SummaryGarlic (Allium sativum L.) is a clonally propagated crop that can be infected by many virus species which tend to accumulate year-after-year, leading to yield reductions and varietal degeneration. Therefore, the production and use of virus-free planting material is vital to sustain productivity. In this study, Onion yellow dwarf virus (OYDV; Potyvirus), Garlic common latent virus (GarCLV; Carlavirus), Shallot latent virus (SLV; Carlavirus), and Garlic virus X (GarV-X; Allexivirus) were detected in cloves of the commercial garlic cultivar, ‘G-1’ (‘Jamuna Safed’) by direct antigen-coated enzyme-linked immunosorbent assay (DAC-ELISA). DAC-ELISA was performed using specific antisera against each virus species, and confirmed through reverse transcription-polymerase chain reactions (RT-PCR) using virus or genus-specific oligonucleotide primers. To obtain virus-free plants of ‘G-1’, cloves were subjected to solar heat treatment for 5, 10, or 15 d, or to hot air treatment (at 37°C, 40°C, or 42°C for 7, 14, or 21 d) combined with meristem isolation and in vitro culture, then indexed for all viruses using DAC-ELISA and RT-PCR. Meristems from solar heat-treated or hot air-treated cloves regenerated after 90 d and 45 d in culture, respectively. Solar heat treatment for 15 d resulted in 17 - 18% regeneration, and all were free from GarCLV, SLV, and OYDV. However, when solar heat-treated for 10 d, only 66% of the 17 - 18% regenerated plants were free from all viruses, including GarV-X. Hot air treatment at 37°C or 40°C eliminated GarCLV, SLV, and OYDV in 20 - 38% and 42 - 62% of regenerated plants, respectively, for the different durations of exposure. However, GarV-X could not be eliminated from any of the regenerated plants by hot air treatment, irrespective of the duration of exposure. Meristems from cloves that had been hot air-treated at 42°C resulted in 50 - 66% regeneration, of which 53 - 57% were free from GarCLV, SLV, and OYDV when treated for 7 d or 14 d, and 29% were free from all viruses when treated for 21 d. For most treatments, an increase in the duration of exposure to heat resulted in reduced regeneration, but increased the rate of recovery of virus-free plants. To our knowledge, this is the first study to report the use of solar treatment for virus elimination in garlic and the development of an efficient tissue culture protocol for the production of virus-free garlic plants using different thermotherapy treatments coupled with meristem tip culture.