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1.
Arch Virol ; 164(11): 2849-2852, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31502078

RESUMO

Arracacha virus B type (AVB-T) and oca (AVB-O) strains from arracacha (Arracacia xanthorrhiza) and oca (Oxalis tuberosa) samples collected in 1975 and two additional isolates obtained from arracacha (AVB-PX) and potato (AVB-6A) in Peru in 1976 and 1978, respectively, were studied. In its host responses and serological properties, AVB-PX most resembled AVB-T, whereas AVB-6A most resembled AVB-O. Complete genomic sequences of the RNA-1 and RNA-2 of each isolate were obtained following high-throughput sequencing of RNA extracts from isolates preserved for 38 (AVB-PX) or 32 (the other 3 isolates) years, and compared with a genomic sequence of AVB-O obtained previously (PV-0082). RNA-2 was unexpectedly divergent compared to RNA-1, with the nucleotide (nt) sequence identity of different AVB isolates varying by up to 76% (RNA-2) and 89% (RNA-1). The coat protein amino acid sequences were the most divergent, with AVB-O and AVB-6A having only 68% identity to AVB-T and AVB-PX. Since the RNA2 sequence differences between the two isolate groupings also coincided with host range, symptom, and serological differences, AVB demonstrates considerable intraspecific divergence.


Assuntos
Genoma Viral/genética , RNA Viral/genética , Secoviridae/genética , Sequência de Aminoácidos , Sequência de Bases , Proteínas do Capsídeo/genética , Sequenciamento de Nucleotídeos em Larga Escala , Magnoliopsida/virologia , Oxalidaceae/virologia , Peru , Doenças das Plantas/virologia , Secoviridae/isolamento & purificação , Solanum tuberosum/virologia
2.
Arch Virol ; 164(11): 2747-2759, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31502079

RESUMO

RNA silencing is a major antiviral mechanism in plants, which is counteracted by virus-encoded proteins with silencing suppression activity. ORFs encoding putative silencing suppressor proteins that share no structural or sequence homology have been identified in the genomes of four criniviruses. In this study, we investigated the RNA silencing suppression activity of several proteins encoded by the RNA1 (RdRp, p22) and RNA2 (CP, CPm and p26) of cucurbit chlorotic yellows virus (CCYV) using co-agroinfiltration assays on Nicotiana benthamiana plants. Our results indicate that p22 is a suppressor of local RNA silencing that does not interfere with cell-to-cell movement of the RNA silencing signal or with systemic silencing. Furthermore, comparisons of the suppression activity of CCYV p22 with that of two other well-known crinivirus suppressors (CYSDV p25 and ToCV p22) revealed that CCYV p22 is a weaker suppressor of local RNA silencing than the other two proteins. Finally, a comparative sequence analysis of the p22 genes of seven Greek CCYV isolates was performed, revealing a high level of conservation. Taken together, our research advances our knowledge about plant-virus interactions of criniviruses, an emergent group of pathogens that threatens global agriculture.


Assuntos
Crinivirus/genética , Interferência de RNA/fisiologia , RNA Viral/genética , Tabaco/virologia , Proteínas do Core Viral/genética , Genoma Viral/genética , Interações Hospedeiro-Patógeno/genética , Doenças das Plantas/virologia
3.
Arch Virol ; 164(11): 2891-2894, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31506787

RESUMO

Contigs with sequence similarity to potato virus P (PVP), which belongs to the genus Carlavirus, were identified by high-throughput sequencing analysis in potato tubers collected from a farmer's potato production field in Surazhevka, Artyom, Primorskiy Krai (Russia) in 2018. The complete genome sequence of this virus consisted of 8,394 nucleotides, excluding the poly(A) tail. This is the first report of PVP being detected outside South America. The isolate had high sequence similarity to PVP isolates from Argentina and Brazil, but low sequence similarity was observed in the genes encoding the RNA-dependent RNA polymerase (69% nucleotide sequence identity and 80% amino acid sequence identity) and coat protein (78% nucleotide sequence identity and 89% amino acid sequence identity). Phylogenetic analysis revealed that this PVP-like virus clustered with known PVP isolates but was distinct from them. Comparison of the sequences using the classification criteria of the ICTV indicated that this PVP-like virus is a strain of PVP.


Assuntos
Carlavirus/genética , Genoma Viral/genética , Doenças das Plantas/virologia , Solanum tuberosum/virologia , Sequência de Aminoácidos , Proteínas do Capsídeo/genética , Carlavirus/classificação , Carlavirus/isolamento & purificação , RNA Polimerases Dirigidas por DNA/genética , Sequenciamento de Nucleotídeos em Larga Escala , RNA Viral/genética , Federação Russa , Sequenciamento Completo do Genoma
5.
Arch Virol ; 164(11): 2873-2875, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31432269

RESUMO

A novel bipartite begomovirus infecting begomovirus-resistant tomato plants was detected via Illumina sequencing analysis, and its genome sequence was confirmed by Sanger sequencing. The DNA-A (2627 nt) and DNA-B (2587 nt) have a genome organization that is typical of New World bipartite begomoviruses, sharing 82.5% identity with tomato golden leaf distortion virus and 75.1% identity with sida chlorotic vein virus. Based on the current classification criteria for begomoviruses, this isolate should be considered a member of a new species, and the name "tomato interveinal chlorosis virus-2" (ToICV2) is proposed for this virus.


Assuntos
Begomovirus/classificação , Begomovirus/genética , Genoma Viral/genética , Lycopersicon esculentum/virologia , Sequência de Bases , Begomovirus/isolamento & purificação , Brasil , DNA Viral/genética , Doenças das Plantas/virologia , Análise de Sequência de DNA , Sequenciamento Completo do Genoma
6.
Arch Virol ; 164(11): 2799-2804, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31440810

RESUMO

Thrips palmi transmits the tospoviruses watermelon bud necrosis (WBNV) and groundnut bud necrosis virus (GBNV) in persistent propagative way. Little is known about the T. palmi-WBNV and -GBNV relationship. In this study, we report the effects of WBNV and GBNV infection on the life history traits of T. palmi. Both WBNV and GBNV had some negative effects on the adult life span, fecundity and survival of T. palmi as compared to non-exposed T. palmi. Tospovirus exposure favoured a female-biased ratio in the experimental population.


Assuntos
Insetos Vetores/virologia , Doenças das Plantas/virologia , Tisanópteros/virologia , Tospovirus/crescimento & desenvolvimento , Animais , Feminino , Masculino , Plantas/virologia , Tospovirus/genética
7.
Arch Virol ; 164(11): 2805-2810, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31451963

RESUMO

Physalis peruviana is a perennial solanaceous plant that has recently been established as a commercial crop in Brazil. This work reports the near-complete genome sequence, particle morphology, and plant host responses to a putative new sobemovirus, named "physalis rugose mosaic virus". The virus, characterized by isometric particles of ca. 30 nm in diameter, causes foliar symptoms of mosaic, malformation and blistering, accompanied by stunting. The near-complete genome sequence comprises 4175 nucleotides and contains five open reading frames that are similar to those of other sobemoviruses. In addition to P. peruviana, the new virus systemically infected Capsicum annuum, Nicotiana tabacum and Solanum lycopersicum by mechanical inoculation. Thus, this virus may cause disease in these crops in the field.


Assuntos
Genoma Viral/genética , Vírus do Mosaico/classificação , Vírus do Mosaico/crescimento & desenvolvimento , Physalis/virologia , Doenças das Plantas/virologia , Vírus de Plantas/classificação , Vírus de Plantas/genética , Brasil , Capsicum/virologia , Lycopersicon esculentum/virologia , Vírus do Mosaico/genética , Vírus de Plantas/crescimento & desenvolvimento , RNA Viral/genética , Tabaco/virologia
8.
Plant Dis ; 103(10): 2527-2535, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31432775

RESUMO

Ramu stunt is a serious disease of sugarcane, currently only reported from Papua New Guinea. It is found in both commercial sugarcane grown on the Ramu Agri Industries Limited (RAIL) estate and in chewing canes (Saccharum officinarum L.) grown in village gardens. The vector of Ramu stunt disease is the island sugarcane planthopper, Eumetopina flavipes Muir. Here we report on the successful transmission of Ramu stunt using E. flavipes and verify that the disease is caused by Ramu stunt virus, a virus with homology to the genus Tenuivirus. Diagnostic reverse transcription PCR screening, with partial genome sequencing and viral protein characterization, was used for confirmation. Disease surveys were undertaken on the RAIL estate, along roadsides, and in village gardens in parts of Papua New Guinea. When the disease was identified, partial genome sequencing of the virus was performed to assess the extent of genome variability among isolates. The disease was less common than predicted from early surveys based on symptoms alone, and genotypic variation was associated with geographic location.


Assuntos
Hemípteros , Saccharum , Tenuivirus , Animais , Hemípteros/virologia , Papua Nova Guiné , Doenças das Plantas/virologia , Saccharum/virologia , Tenuivirus/fisiologia
9.
J Agric Food Chem ; 67(33): 9241-9253, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31369258

RESUMO

Antiviral compounds targeting viral replicative processes have been studied as an alternative for the control of begomoviruses. Previously, we have reported that the peptide AmPep1 has strong affinity binding to the replication origin sequence of tomato yellow leaf curl virus (TYLCV). In this study, we describe the mechanism of action of this peptide as a novel alternative for control of plant-infecting DNA viruses. When AmPep1 was applied exogenously to tomato and Nicotiana benthamiana plants infected with TYLCV, a decrease in the synthesis of the two viral DNA strands (CS and VS) was observed, with a consequent delay in the development of disease progress in treated plants. The chemical mechanism of action of AmPep1 was deduced using Raman spectroscopy and molecular modeling showing the formation of chemical interactions such as H bonds and electrostatic interactions and the formation of π-π interactions between both biomolecules contributing to tampering with the viral replication.


Assuntos
Amaranthus/química , Antivirais/química , Antivirais/farmacologia , Begomovirus/efeitos dos fármacos , Peptídeos/química , Peptídeos/farmacologia , RNA Viral/química , Replicação Viral/efeitos dos fármacos , Begomovirus/química , Begomovirus/genética , Begomovirus/fisiologia , Sequências Repetidas Invertidas/efeitos dos fármacos , Lycopersicon esculentum/virologia , Doenças das Plantas/virologia , Proteínas de Plantas/química , RNA Viral/genética , Tabaco/virologia
10.
An Acad Bras Cienc ; 91(3): e20180224, 2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31365647

RESUMO

Virus diseases of cool season vegetable crops (mainly cabbage, white and red head cabbage, broccoli, kale, radish, rocket salad, garden cress, and turnip) were surveyed in Bafra Plain, Turkey during winter 2017, and 2018. Leaf samples were collected from different species of the Brassicaceae family showing mosaic, mottling, necrotic spots, malformation, and chlorosis symptoms. These samples were tested for the presence of Cauliflower mosaic virus (CaMV), Cucumber mosaic virus (CMV), Beet western yellows virus (BWYV), Radish mosaic virus (RaMV), Turnip mosaic virus (TuMV), Turnip yellow mosaic virus (TYMV), and Turnip yellows virus (TuYV) by biological and serological methods. A total of 455 samples were collected from cole crop fields and tested for the seven viruses by double-antibody sandwich ELISA using specific polyclonal antibodies. According to the results, out of these, 7 % of the samples were infected by at least one of these viruses. TuMV was the most prevalent virus detected in cole crops. TuMV, CaMV, and CMV were detected in 3 %, 2 %, and 2 % of infected samples, respectively, and the infection rate of these three viruses changed significantly among Brassica species.


Assuntos
Brassicaceae/virologia , Produtos Agrícolas/virologia , Doenças das Plantas/virologia , Brassicaceae/classificação , Estações do Ano , Turquia
11.
J Agric Food Chem ; 67(36): 10000-10009, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31442045

RESUMO

Improving plant resistance against systemic diseases remains a challenging research topic. In this study, we developed a dual-action pesticide-loaded hydrogel with the capacity to significantly induce plant resistance against tobacco mosaic virus (TMV) infection and promote plant growth. We produced an alginate-lentinan-amino-oligosaccharide hydrogel (ALA-hydrogel) by coating the surface of an alginate-lentinan drug-loaded hydrogel (AL-hydrogel) with amino-oligosaccharide using electrostatic action. We determined the formation of the amino-oligosaccharide film using various approaches, including Fourier transform infrared spectrometry, the ζ potential test, scanning electron microscopy, and elemental analysis. It was found that the ALA-hydrogel exhibited stable sustained-release activity, and the release time was significantly longer than that of the AL-hydrogel. In addition, we demonstrated that the ALA-hydrogel was able to continuously and strongly induce plant resistance against TMV and increase the release of calcium ions to promote Nicotiana benthamiana growth. Meanwhile, the ALA-hydrogel maintained an extremely high safety to organisms. Our findings provide an alternative to the traditional approach of applying pesticide for controlling plant viral diseases. In the future, this hydrogel with the simple synthesis method, green synthetic materials, and its efficiency in the induction of plant resistance will attract increasing attention and have good potential to be employed in plant protection and agricultural production.


Assuntos
Antivirais/química , Preparações de Ação Retardada/farmacologia , Portadores de Fármacos/química , Lentinano/química , Lentinano/farmacologia , Doenças das Plantas/virologia , Vírus do Mosaico do Tabaco/fisiologia , Tabaco/virologia , Alginatos/química , Antivirais/farmacologia , Preparações de Ação Retardada/química , Resistência à Doença , Hidrogéis/química , Doenças das Plantas/imunologia , Tabaco/imunologia
12.
Plant Dis ; 103(9): 2221-2230, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31287755

RESUMO

Potato virus Y (PVY) exists as several strains with distinct symptomology and tuber yield effects in different potato varieties. Recently, new recombinant strains have proliferated and dominated local populations around the world. In this study, PVYO, PVYN:O, PVYN-Wi, and PVYNTN strains were tracked across Canada from 2014 to 2017, showing rapid evolution of populations away from the traditionally dominant PVYO to recombinants PVYN-Wi (western Canada) and PVYNTN (eastern Canada). Simultaneously, 30 potato varieties were inoculated with PVYO, PVYN:O, and PVYNTN in controlled greenhouse experiments. Foliar symptoms of primary (mechanical inoculation mimicking aphid infection) and secondary (tuber seedborne) infection were cataloged, and tuber yield measured. On average, and generally similar in primary and secondary infection, symptom expression and yield reduction were most severe with PVYO, followed by PVYN:O and PVYNTN. Strong mosaic symptoms were most commonly expressed with PVYO infection, and only seen with PVYN:O or PVYNTN in 15 and 3 varieties, respectively. Across variety-strain combinations, yield reduction was correlated with symptom severity, most strongly in PVYO-infected plants (e.g., AC Chaleur, Beljade, Envol, Norland, and Pacific Russet), and four varieties exhibited tuber necrotic ringspot disease with PVYNTN (AC Chaleur, Envol, Pacific Russet, and Yukon Gold).


Assuntos
Doenças das Plantas , Potyvirus , Vírus Reordenados , Solanum tuberosum , Replicação Viral , Animais , Cruzamento , Canadá , Doenças das Plantas/virologia , Potyvirus/genética , Potyvirus/fisiologia , Vírus Reordenados/fisiologia , Solanum tuberosum/virologia
13.
Plant Dis ; 103(9): 2345-2352, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31306086

RESUMO

Ti ringspot is an emerging foliar disease of the ti plant (Cordyline fruticosa) in Hawaii that is quickly spreading throughout the islands. Symptoms include small chlorotic ringspots on leaves that often coalesce to form larger lesions. Although several virus species have been discovered in symptomatic plants, none have been associated with these symptoms. Here, we report and characterize a novel virus closely associated with ti ringspot symptoms in Hawaii. The presence of double membrane bodies approximately 85 nm in diameter in symptomatic cells and sequence analyses of five genomic RNA segments obtained by high-throughput sequencing indicate that this virus is most closely related to members of the plant virus genus Emaravirus. Phylogenetic and sequence homology analyses place this virus on a distinct clade within the Emaravirus genus along with High Plains wheat mosaic emaravirus, blue palo verde broom virus, and Raspberry leaf blotch emaravirus. Sequence identity values with taxonomically relevant proteins indicate that this represents a new virus species, which we are tentatively naming ti ringspot-associated virus (TiRSaV). TiRSaV-specific reverse transcription PCR assays detected the virus in several experimental herbaceous host species following mechanical inoculation. TiRSaV was also detected in eriophyid mites collected from symptomatic ti plants, which may represent a putative arthropod vector of the virus.


Assuntos
Bunyaviridae , Cordyline , Animais , Bunyaviridae/classificação , Bunyaviridae/genética , Bunyaviridae/fisiologia , Cordyline/virologia , Hawaii , Filogenia , Doenças das Plantas/virologia
14.
Plant Dis ; 103(9): 2367-2373, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31318645

RESUMO

Sugarcane yellow leaf virus (SCYLV), the causal agent of yellow leaf, is widespread in Florida. Two field trials were set up, one on organic soil and one on mineral soil, to investigate the rate and timing of sugarcane infection by SCYLV under field conditions and the effect of the virus on yield. Each trial consisted of plots planted with healthy or SCYLV-infected seed cane of two commercial cultivars. Virus prevalence varied from 83 to 100% in plots planted with infected seed cane regardless of cultivar, location, and crop season. On organic soil, plants of virus-free plots became progressively infected in plant cane and first ratoon crops. On mineral soil, healthy sugarcane became initially infected in the first ratoon crop. After three crop seasons, the highest SCYLV prevalence rates were 33 and 7% on organic and mineral soils, respectively. No significant negative effect of SCYLV on yield was found in plant cane crop regardless of cultivar and soil type. However, yield reductions in ratoon crops varied from nonsignificant to 27% depending on cultivar and soil type. Low virus prevalence observed after three crop seasons suggested that planting virus-free seed cane should limit the impact of SCYLV on sugarcane production in Florida.


Assuntos
Luteoviridae , Saccharum , Solo , Florida , Luteoviridae/fisiologia , Minerais/química , Doenças das Plantas/virologia , Saccharum/virologia , Solo/química
15.
Plant Dis ; 103(9): 2199-2203, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322493

RESUMO

Viral diseases are a limiting factor to wheat production. Viruses are difficult to diagnose in the early stages of disease development and are often confused with nutrient deficiencies or other abiotic problems. Immunological methods are useful to identify viruses, but specific antibodies may not be available or require high virus titer for detection. In 2015 and 2017, wheat plants containing Wheat streak mosaic virus (WSMV) resistance gene, Wsm2, were found to have symptoms characteristic of WSMV. Serologically, WSMV was detected in all four samples. Additionally, High Plains wheat mosaic virus (HPWMoV) was also detected in one of the samples. Barley yellow dwarf virus (BYDV) was not detected, and a detection kit was not readily available for Triticum mosaic virus (TriMV). Initially, cDNA cloning and Sanger sequencing were used to determine the presence of WSMV; however, the process was time-consuming and expensive. Subsequently, cDNA from infected wheat tissue was sequenced with single-strand, Oxford Nanopore sequencing technology (ONT). ONT was able to confirm the presence of WSMV. Additionally, TriMV was found in all of the samples and BYDV in three of the samples. Deep coverage sequencing of full-length, single-strand WSMV revealed variation compared with the WSMV Sidney-81 reference strain and may represent new variants which overcome Wsm2. These results demonstrate that ONT can more accurately identify causal virus agents and has sufficient resolution to provide evidence of causal variants.


Assuntos
Doenças das Plantas , Vírus de Plantas , Análise de Sequência , Triticum , Bunyaviridae/classificação , Bunyaviridae/genética , Luteovirus/classificação , Luteovirus/genética , Nanoporos , Doenças das Plantas/virologia , Vírus de Plantas/classificação , Vírus de Plantas/genética , Potyviridae/classificação , Potyviridae/genética , Análise de Sequência/normas , Triticum/virologia
16.
Plant Dis ; 103(9): 2179-2183, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322494

RESUMO

Potato virus Y (PVY) is among the most economically impactful potato pathogens, yet the spread of PVY from infected seed potatoes within commercial potato fields has not been adequately studied. Test lots containing various seed-borne PVY levels were created by mixing different proportions of seed pieces from healthy and infected tubers drawn from the same seed source. These seed lots were planted in commercial potato fields near the Teton Seed Potato Management Area from 2010 to 2012. Regression analyses on data from these test plots produced models of the in-season spread of PVY originating from infected seed. Conventional ordinary least squares techniques were supplemented with the use of quantile regression; the resulting models indicate the significance of seed-borne PVY on end-of-season infection levels and highlight the need of seed potato buyers to review postharvest testing results.


Assuntos
Doenças das Plantas , Tubérculos , Potyvirus , Solanum tuberosum , Agricultura , Doenças das Plantas/prevenção & controle , Doenças das Plantas/virologia , Tubérculos/virologia , Solanum tuberosum/virologia
17.
Plant Dis ; 103(9): 2315-2321, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322977

RESUMO

Typically, the detection of a plant virus within its vector is carried out on the entire insect body. This process can be a possible source of confusion in the quantification of transmissible virus particles for styletborne viruses such as Potato virus Y (PVY), since the transmissible virus fraction is the one only retained in the aphid vector's mouthparts. The objective of this study was to develop and validate the quantitative PCR method for the detection and quantification of PVY in the vector's stylet. Using a specific method based on TaqMan chemistry with higher sensitivity than conventional reverse transcription PCR, this study reveals that a significant amount of the virus is enclosed within the dissected stylets of Myzus persicae. Because this quantification only concerns the portion of the virus attached to the stylets, uniformity was observed in the recorded numbers of virus targets. This novel assay is applicable to several PVY strains as a rapid and sensitive detection method for use in PVY research and offers a convenient tool for deciphering the mechanism of Potyvirus acquisition.


Assuntos
Afídeos , Genoma Viral , Potyvirus , Animais , Afídeos/virologia , Vetores de Doenças , Doenças das Plantas/virologia , Reação em Cadeia da Polimerase , Potyvirus/genética
18.
Arch Virol ; 164(9): 2367-2370, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31256263

RESUMO

Garlic mite-borne filamentous virus is one of the oldest recognized allexivirus species but, paradoxically, one with the least well studied member viruses. In this paper, we review the history of this taxon and highlight problems in designating a holotype (exemplar isolate). Analyses are presented that suggest that GarMbFV is conspecific with Garlic virus A, and therefore the former taxon should be abolished.


Assuntos
Vetores Aracnídeos/virologia , Flexiviridae/classificação , Alho/virologia , Ácaros/virologia , Doenças das Plantas/virologia , Animais , Vetores Aracnídeos/fisiologia , Flexiviridae/genética , Flexiviridae/isolamento & purificação , Ácaros/fisiologia , Filogenia
19.
Plant Dis ; 103(10): 2652-2664, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31322490

RESUMO

Cassava brown streak disease (CBSD), caused by cassava brown streak ipomoviruses (CBSIs), has become the most debilitating biotic stress to cassava production in East and Central Africa. Lack of CBSD-resistant varieties has necessitated the search for alternative control measures. Most smallholder farmers reuse stems from previous crops for planting in the new season. Recycling planting material in this way can lead to "degeneration" owing to the compounding effects of disease. In this study, degeneration was defined as the increase in CBSD incidence and reduction in marketable root yield over time. An experiment was established to study the rates of degeneration in selected cassava varieties Chereko, KBH2002_135, Kipusa, Kizimbani, and Mkuranga1 and cultivars Kiroba and Kikombe under high-CBSD inoculum conditions in Bagamoyo, Tanzania from 2013 to 2017. The experiment was replicated across two seasons: the first planted during the long rains (Masika) between March and June and the second planted during the short rains (Vuli) between October and December. Mean abundance of the whitefly vector (Bemisia tabaci) was much greater during the Vuli season (>19 insects per plant) than the Masika season (<2 insects per plant). CBSD shoot symptoms occurred naturally and were observed only on Kikombe, Kiroba, and Kipusa. New materials had overall lower CBSD shoot incidences (1.5%) compared with recycled materials (6.9%) in Masika, although no significant differences were obvious in Vuli. However, Masika (8.7%) had an overall lower CBSD shoot incidence than Vuli (16.5%) in the varieties that had shoot symptoms. CBSD root incidences were higher in Vuli (10.3%) than Masika (4.4%), and root yields in Masika (29.4 t/ha) were significantly greater than those in Vuli (22.5 t/ha). The highest percentage of roots rendered unusable owing to CBSD was observed in Vuli. There was significantly higher unusable root incidence in recycled materials (3.7%) than in new materials (1.4%) in Masika but not in Vuli. Overall root yield was similar between recycled and new materials in either season. Significant reductions in root yield over the course of the experiment were observed both in Masika and Vuli, whereas changes in marketable yield were significant only in Masika. Differences in the response of varieties to degeneration led to the identification of four degeneration patterns, namely "strong," "moderate," "mild," and "delayed" degeneration. The strongest effects of degeneration were most obvious in the susceptible cultivar (Kikombe), which also had the lowest marketable yield in either season. Seasonal differences were a key driver of degeneration, because its effects were much greater in Vuli than Masika. To the best of our knowledge, this work reports the first study of degeneration caused by cassava viruses.[Formula: see text] Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.


Assuntos
Manihot , Potyviridae , África Central , Animais , Manihot/microbiologia , Manihot/virologia , Doenças das Plantas/virologia , Potyviridae/fisiologia , Tanzânia
20.
Arch Virol ; 164(10): 2459-2467, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31286220

RESUMO

Tobacco vein banding mosaic virus (TVBMV) is of increasing importance in tobacco production. Knowledge of the genetic structure and variability of the virus population is vital for developing sustainable management. In this study, 24 new TVBMV isolates from Sichuan Province together with 46 previous isolates were studied based on their coat protein sequences. Two distinguishable clades were supported by phylogenetic analysis. The summary statistics PS, AI and MC showed a strong TVBMV-geography association between the isolates from Southwest China (SW) and Mainland China (MC). Further analysis indicated that the spatial genetic structure of TVBMV populations is likely to have been caused by natural selection. Phylogeographic analysis provided strong support for spatial diffusion pathways between the Southwest and Northwest tobacco-producing regions. The TVBMV CP gene was found to be under negative selection, and no significant positive selection of amino acids was detected in the SW group; however, the isolates of the MC group experienced significant positive selection pressure at the first and third amino acid sites of CP. This study suggests that natural selection and habitat heterogeneity are important evolutionary mechanisms affecting the genetic structure of the TVBMV population.


Assuntos
Variação Genética , Doenças das Plantas/virologia , Potyvirus/classificação , Potyvirus/genética , Tabaco/virologia , Proteínas do Capsídeo/genética , China , Filogeografia , Potyvirus/isolamento & purificação , Seleção Genética , Análise de Sequência de DNA
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