| 1. |
- Just, Kadri, et al.
(författare)
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Detection of Tomato yellow leaf curl virus in imported tomato fruit in northern Europe
- 2014
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Ingår i: Plant Pathology. - : Wiley. - 0032-0862 .- 1365-3059. ; 63, s. 1454-1460
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Tidskriftsartikel (refereegranskat)abstract
- Imported tomato fruits infected with Tomato yellow leaf curl virus (TYLCV) were identified on the market in northern Europe using paper-based FTA Classic Cards (Whatman), polymerase chain reaction (PCR) and partial DNA sequence analysis. Trade tomatoes originating from southern Europe, Africa and the Middle East were sampled in Estonia and Sweden, and tested for infection with begomoviruses. Out of 100 batches analysed with five fruits sampled in each batch (58 batches from Estonia and 42 from Sweden), 20 batches were positive (16 from Estonia and four from Sweden). Rolling circle amplification (RCA) and full-length genome sequence analysis of one isolate collected in Estonia and one isolate in Sweden, revealed highest nucleotide sequence identity at 99% to TYLCV-IL for the Estonian isolate and at 97% to TYLCV-Mld for the Swedish isolate. In this study, TYLCV was identified for the first time in imported tomato fruits on the market in northern Europe. FTA cards proved to be an effective means to collect, extract and store begomovirus DNA from tomato fruits and the subsequent molecular analysis.
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| 2. |
- Just, Kadri, et al.
(författare)
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Infectivity of Tomato yellow leaf curl virus isolated from imported tomato fruit in Estonia
- 2017
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Ingår i: Žemdirbystė. - : LITHUANIAN RESEARCH CENTRE AGRICULTURE & FORESTRY. - 1392-3196 .- 2335-8947. ; 104:1, s. 47-52
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Tidskriftsartikel (refereegranskat)abstract
- There is a risk that Tomato yellow leaf curl virus (TYLCV) and its vector, whiteflies of the Bemisia tabaci species complex, will become established in greenhouses in temperate regions of the world, including northern Europe. In this study, TYLCV isolated from imported tomato fruit in Estonia (originating from Spain) was shown to be able to infect plants of tomato and Nicotiana benthamiana using Agrobacterium-mediated inoculation with an infectious clone as well as using biolistic delivery of products from rolling circle amplification (RCA). A 1.8-mer genomic construct of TYLCV was engineered and efficiently agroinfiltrated into plants of tomato and N. benthamiana, and induced symptoms characteristic of natural infection. With Agrobacterium-mediated inoculation, the infection efficiency was 100% for both tomato and N. benthamiana, whereas biolistic inoculation using RCA products resulted in efficiencies of 57% and 36%, respectively. Particle bombardment with monomeric linear genome failed to produce any infection in tomato or N. benthamiana. The genome of TYLCV amplified from tomato fruit was infectious confirming that tomato fruit may serve as a source of virus inoculum. This is the first report of agroinfiltration and particle bombardment assay using TYLCV DNA derived from infected tomato fruit tissue.
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| 3. |
- Leke, Walter Nkeabeng, et al.
(författare)
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Ageratum conyzoides: A host to a unique begomovirus disease complex in Cameroon
- 2012
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 163, s. 229-237
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Tidskriftsartikel (refereegranskat)abstract
- Ageratum conyzoides (goat weed) is a widespread uncultivated species in Cameroon that exhibits leaf curldisease (LCD) symptoms suggestive of begomovirus infection. In Asia, different begomovirus-satellitecomplexes have been identified in A. conyzoides. The objective of this study was to determine the identityof the suspect begomoviruses and their associated satellites in A. conyzoides in Cameroon. The resultsindicated that all three symptomatic A. conyzoides plants examined were infected with a new begomovirusspecies, herein named Ageratum leaf curl Cameroon virus (ALCCMV). The ALCCMV genomesequences shared their highest identity, at 84.3-88.5%, with a group of tomato-infecting begomovirusesfrom West Africa. In addition, a betasatellite and an alphasatellite were cloned from the same symptomaticA. conyzoides plants. The betasatellite sequences shared limited sequence identity at 37% orless with the betasatellite Cotton leaf curl Gezira betasatellite, and the new betasatellite species is hereinnamed Ageratum leaf curl Cameroon betasatellite (ALCCMB). The alphasatellite shared 80% nt identitywith Tomato leaf curl Cameroon alphasatellite (ToLCCMA), and the new alphasatellite species is hereinnamed Ageratum leaf curl Cameroon alphasatellite (ALCCMA). In addition, two fragments containingbegomovirus-alphasatellite sequences were cloned from sample AGLI4, and they were related to thedefecting interfering molecule (Y14167) associated with Ageratum yellow vein virus from Asia. Theseresults suggest that the begomoviral-satellite complexes infecting A. conyzoides in Cameroon may be ascomplex or more so, to species and strains reported thus far from Asia.
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| 4. |
- Leke, Walter Nkeabeng, et al.
(författare)
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Molecular characterization of begomoviruses and DNA satellites associated with okra leaf curl disease in Cameroon
- 2013
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 174, s. 116-125
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Tidskriftsartikel (refereegranskat)abstract
- Okra leaf curl disease (OLCD) is the most important viral disease of okra in West Africa. In this study, a complex of begomoviruses and associated DNA satellites were identified in symptomatic okra plants from southwestern Cameroon. Sequence analyses showed that two of the plants (Lik1 and Njo5) were infected with a begomovirus being a recombinant of cotton leaf curl Gezira virus (CLCuGeV) and okra yellow crinkle virus (OYCrV). The recombinant genome shared highest nucleotide identity with isolates of CLCuGeV at 87.8% and is therefore considered to be member of a new begomovirus species, Okra leaf curl Cameroon virus (OLCuCMV). One plant (Mue5) was infected by a begomovirus with 95.8% nucleotide identy to CLCuGeV, while in the plants Lik1, Muel and Njo5, a begomovirus was identified showing highest nucleotide identity at 93.7% with OYCrV. The nucleotide comparisons and phylogenetic analyses suggest that these isolates represent new Cameroonian strains of CLCuGeV and OYCrV (CLCuGeV-CM and OYCrV-CM). Mixed infection of OLCuCMV and OYCrV-CM was found in two of the plants. A betasatellite and two divergent alphasatellites were also associated with the begomoviruses. The betasatellite was identified as cotton leaf curl Gezira betasatellite (CLCuGeB) with the highest nucleotide identity at 93.3% to othei African isolates of CLCuGeB. The alphasatellites, herein named Alpha-1 and Alpha-2, shared 973% and 95.2% identity, respectively, with cotton leaf curl Gezira alphasatellite (CLCuGeA) and okra leaf curl Burkina Faso alphasatellite (OLCuBFA). These collective results emphasize the extent of diversity among okra-infecting begomovirus-satellite complexes in western Africa. (C) 2013 Elsevier B.V. All rights reserved.
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| 5. |
- Sattar, Muhammad Naeem, et al.
(författare)
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Compatibility and interaction of begomoviruses and DNA-satellites causing leaf curl disease in Asia, Africa and Mediterranean Region
- 2019
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Ingår i: European Journal of Plant Pathology. - : Springer Science and Business Media LLC. - 0929-1873 .- 1573-8469. ; 155, s. 111-124
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Tidskriftsartikel (refereegranskat)abstract
- A complex of begomoviruses and their associated DNA-satellites is causing leaf curl diseases in Asia, Africa and the Mediterranean Region. Begomoviruses and DNA-satellites native to Asia and Africa are distinct from each other. Different combinations of geographically distinct monopartite begomoviruses, betasatellites and an alphasatellite were analyzed in infection experiments: cotton leaf curl Kokhran virus (CLCuKoV) and cotton leaf curl Multan virus (CLCuMuV) from Pakistan along with their associated cotton leaf curl Multan betasatellite (CLCuMuB); okra yellow crinkle virus (OYCrV), cotton leaf curl Gezira betasatellite (CLCuGeB), ageratum leaf curl Cameroon betasatellite (ALCCMB) and ageratum leaf curl Cameroon alphasatellite (ALCCMA) from Cameroon; tomato yellow leaf curl virus (TYLCV) from the Mediterranean Region. The infectivity assays were carried out in the model host species Nicotiana benthamiana and agro-infectious clones containing partial tandem repeats of the begomovirus and satellite genomes. The tested begomoviruses from different regions could functionally interact with non-cognate betasatellites and alphasatellite. Plants co-inoculated with CLCuKoV/CLCuGeB or CLCuMuV/CLCuGeB developed, for both combinations, more severe symptoms than with the begomovirus alone and the infection was verified by Southern blot hybridization. Nonetheless, CLCuKoV and CLCuMuV were shown also to support infection by ALCCMB, whereas OYCrV and TYLCV were able to support infection with CLCuMuB, ALCCMB and CLCuGeB. Moreover, all begomoviruses from different geographical origins supported ALCCMA from Africa. The results confirm that geographically diverse begomoviruses can functionally interact with non-cognate DNA-satellites, which may cause the emergence of new begomovirus-satellite complexes. Possibly, exchange of DNA-satellites may occur across continents leading to the emergence of new viral diseases.
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| 6. |
- Sattar, Muhammad Naeem, et al.
(författare)
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Cotton leaf curl disease - an emerging threat to cotton production worldwide
- 2013
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Ingår i: Journal of General Virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 94, s. 695-710
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Forskningsöversikt (refereegranskat)abstract
- Cotton leaf curl disease (CLCuD) is a serious disease of cotton which has characteristic symptoms, the most unusual of which is the formation of leaf-like enations on the undersides of leaves. The disease is caused by whitefly-transmitted geminiviruses (family Geminiviridae, genus Begomovirus) in association with specific, symptom-modulating satellites (betasatellites) and an evolutionarily distinct group of satellite-like molecules known as alphasatellites. CLCuD occurs across Africa as well as in Pakistan and north-western India. Over the past 25 years, Pakistan and India have experienced two epidemics of the disease, the most recent of which involved a virus and satellite that are resistance breaking. Loss of this conventional host-plant resistance, which saved the cotton growers from ruin in the late 1990s, leaves farmers with only relatively poor host plant tolerance to counter the extensive losses the disease causes. There has always been the fear that CLCuD could spread from the relatively limited geographical range it encompasses at present to other cotton-growing areas of the world where, although the disease is not present, the environmental conditions are suitable for its establishment and the whitefly vector occurs. Unfortunately recent events have shown this fear to be well founded, with CLCuD making its first appearance in China. Here, we outline recent advances made in understanding the molecular biology of the components of the disease complex, their interactions with host plants, as well as efforts being made to control CLCuD.
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| 7. |
- Sattar, Muhammad Naeem
(författare)
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Diversity and interactions of begomoviruses and their associated DNA-satellites
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To study the diversity of begomovirus/DNA-satellite complexes, plants of one crop species (okra; Abelmoschus esculentus) and one weed species (Ageratum conyzoides), both with leaf curling symptoms, were analyzed. Sequence analyses of complete genome components revealed a unique begomovirus/DNA-satellite complex in both plants. Okra was found to harbor infection with viruses of three begomovirus species, including the new recombinant species Okra leaf curl Cameroon virus, as well as one betasatellite and two divergent alphasatellites. The analysis of A. conyzoides revealed infection with a previously un-described complex of a begomovirus, betasatellite and alphasatellite. The results suggest that the diversity of begomoviruses and their associated DNA-satellites in Africa is much higher than previously thought, and that it may be similar to the diversity in Asia. Begomoviruses and satellites from different geographic regions, such as Africa and Asia, are genetically different. To test the compatibility of begomoviruses and satellites from Asia, Africa and the Mediterranean Region, inoculation experiments were carried out in the model host Nicotiana benthamiana using agroinfectious constructs for different begomoviruses and satellites. It was found that the tested begomoviruses and satellites could functionally interact with non-cognate betasatellites and alphasatellites with varying efficiencies. The results showed that the functional requirements for interaction between begomovirus and satellite can be quite relaxed. Thus, it is quite possible that new begomovirus-satellite combinations with components from different geographic regions will be formed, which may overcome plant resistance and increase the host range of begomoviruses. Functional studies were carried out on the betasatellite-associated monopartite begomovirus Cotton leaf curl Kokhran virus. Mutation analyses of the coat protein (CP), V2, C2 and C4 genes showed that CP, V2 and C2 are pathogenicity determinants and that they are involved in facilitating virus movement and maintenance of betasatellites. C4 is responsible for symptom induction, but it was not specifically required to maintain betasatellites.
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| 8. |
- Sattar, Muhammad Naeem, et al.
(författare)
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Effects of the mutation of selected genes of Cotton leaf curl Kokhran virus on infectivity, symptoms and the maintenance of Cotton leaf curl Multan betasatellite
- 2012
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Ingår i: Virus Research. - : Elsevier BV. - 0168-1702 .- 1872-7492. ; 169, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- Cotton leaf curl Kokhran virus (CLCuKoV) is a cotton-infecting monopartite begomovirus (family Geminiviridae).The effects of mutation of the coat protein (CP), V2, C2 and C4 genes of CLCuKoV on infectivityand symptoms in Nicotiana benthamiana were investigated. Each mutation introduced a premature stopcodon which would lead to premature termination of translation of the gene. Mutation of the CP geneabolished infectivity. However, transient expression of the CLCuKoV CP gene under the control of theCauliflower mosaic virus 35S promoter (35S-KoCP), at the point of inoculation, led to a small number ofplants in which viral DNA could be detected by PCR in tissues distal to the inoculation site. Mutations ofthe V2, C2 and C4 genes reduced infectivity. The V2 and C2 mutants did not induce symptoms, whereasthe C4 mutation was associated with attenuated symptoms. Infections of plants with the C4 mutant wereassociated with viral DNA levels equivalent to the wild-type virus, whereas viral DNA levels for the V2mutant were low, detectable by Southern blot hybridisation, and for the C2 mutant were detectable onlyby PCR. Significantly, transient expression of the CLCuKoV C2 gene at the point of inoculation, raisedvirus DNA levels in tissues distal to the inoculation site such that they could be detected by Southernhybridisation, although they remained at well below the levels seen for the wild-type virus, but reducedthe infectivity of the virus. These findings are consistent with earlier mutation studies of monopartitebegomoviruses and our present knowledge concerning the functions of the four genes suggesting that theCP is essential for long distance spread of the virus in plants, the C4 is involved in modulating symptoms,the C2 interferes with host defence and the V2 is involved in virus movement. The results also suggestthat the V2, C2 and C4 may be pathogenicity determinants. Additionally the effects of the mutations ofCLCuKoV genes on infections of the virus in the presence of its cognate betasatellite, Cotton leaf curl Multanbetasatellite (CLCuMuB), were investigated. Mutation of the C4 gene had no effect on maintenanceof the betasatellite, although the betasatellite enhanced symptoms. Inoculation of the C2 mutant withCLCuMuB raised the infectivity of the virus to near wild-type levels, although the numbers of plants inwhich the betasatellite was maintained was reduced, in comparison to wild-type virus infections withCLCuMuB, and viral DNA could not be detected by Southern hybridisation. Transient expression of theC2 gene at the point of inoculation raised virus DNA levels in tissues distal to the inoculation site but alsoreduced the infectivity of the virus and the numbers of plants in which the betasatellite was maintained.CLCuMuB restored the infectivity of the V2 mutant to wild-type levels but only in a small number ofplants was the satellite maintained and infections were non-symptomatic. Although inoculation of theCP mutant with CLCuMuB did not restore infectivity, co-inoculation with 35S-KoCP increased the numberof plants in which the virus could be detected, in comparison to plants inoculated with the mutantand 35S-KoCP, and also resulted in two plants (out of 15 inoculated) in which the betasatellite could bedetected by PCR. This indicates that the V2, C2 and almost certainly the CP are important for the maintenanceof betasatellites by monopartite begomoviruses. The significance of these findings is discussed.
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| 9. |
- Sattar, Muhammad Naeem, et al.
(författare)
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First Identification of Begomoviruses Infecting Tomato With Leaf Curl Disease in Burkina Faso
- 2015
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Ingår i: Plant Disease. - 0191-2917 .- 1943-7692. ; 99, s. 732-733
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Annan publikation (refereegranskat)abstract
- Leaf curl and yellow leaf curl are frequently affecting production of tomato (Solanum lycopersicum) in Burkina Faso, with an incidence of 60% in 1993 (2). However, the specific begomoviruses associated with the disease had not been identified. In January and February 2009, severe leaf curl symptoms coupled with heavy infestations of the whitefly Bemisia tabaci were observed in tomato plants in several parts of Burkina Faso. Leaf samples were collected from symptomatic tomato plants, and total DNA was extracted by CTAB method, or by FTA classic cards (4). PCR using universal coat protein (CP) gene primers (AC1048/AV494) followed by sequence analysis of cloned amplicons indicated infection with Tomato yellow leaf curl Mali virus (TYLCMLV), Tomato leaf curl Mali virus (ToLCMLV), and Pepper yellow vein Mali virus (PeYVMLV), with a mixed infection of the first two viruses in one tomato plant. Two tomato plant samples (Di-14 and Oua-20) from Di and Ouahigouya, respectively, were selected for rolling circle amplification (RCA) and the RCA product was subjected to restriction enzyme analysis. The linearized fragments (∼2.8 kb), which were obtained after digest with the EcoRV restriction enzyme, were cloned into pJET1.2/blunt (Thermo Scientific). Four clones for sample Di-14 (Tom-141, Tom-142, Tom-143b, and Tom-145b), and one clone (Tom-202b) for sample Oua-20 were fully sequenced in both directions and pairwise comparisons were carried out using the STD software (3). Four clones (Tom-141, GenBank accession number LM651400; Tom-142, LM651401; Tom-143b, LM651402; Tom-202b, LM651403) shared 97.7 to 100% identity with each other, and 97.6 to 99.2% with an isolate of TYLCMLV (EU847740) identified from tomato in Ghana. The clone Tom-145b (LM651404) shared 91.2% sequence identity with an isolate of ToLCMLV (AY502936) from Mali (5). All clones from tomato showed four open reading frames (ORFs) (Rep, C2, REn, and C4) on the complementary sense strand, and two ORFs (CP and V2) in the virion sense orientation, similar to previously characterized monopartite begomoviruses. According to the International Committee on Taxonomy of Viruses guidelines for species demarcation in the genus Begomovirus, Tom-141, Tom-142, Tom-143b, and Tom-202b belong to the Ghana strain of TYLCMLV, whereas Tom-145b is a member of a new Burkina Faso strain of ToLCMLV (ToLCMLV-BF). All five clones thus represent monopartite begomoviruses apparently of African origin, and belong to the family Geminiviridae. The three begomovirus species TYLCMLV, ToLCMLV, and PeYVMLV had previously been detected in tomato in West Africa, but this is their first identification in tomato in Burkina Faso. It is also the first report of the Burkina Faso strain of ToLCMLV. After its initial discovery in Mali, West Africa (1), TYLCMLV has also been reported from Cameroon in Central Africa (FM212662), Ethiopia in East Africa (DQ358913), Ghana (EU847740), and now from Burkina Faso.
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| 10. |
- Tzelepis, Georgios, et al.
(författare)
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Detection of Verticillium species in Swedish soils using real‑time PCR
- 2017
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Ingår i: Archives of Microbiology. - : Springer Science and Business Media LLC. - 0302-8933 .- 1432-072X. ; 199, s. 1383-1389
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Tidskriftsartikel (refereegranskat)abstract
- Verticillium species are soilborne plant pathogens, responsible for big yield losses worldwide. Here, we report improved procedures to generate DNA from Verticillium species imbedded in farm soils. Using new genomic sequence information, primers for V. dahliae, V. albo-atrum, V. tricorpus, and V. longisporum were designed. In a survey of 429 samples from intensively farmed soil of two Swedish regions, only V. dahliae and V. longisporum were identified. A bias towards V. longisporum (40%) was seen in the south, whereas V. dahliae was more frequent in the western region (19%). Analyses of soil and leaf samples from 20 sugar beet fields, where foliar wilting had been observed, revealed V. dahliae DNA in all leaf and soil samples and V. longisporum in 18 soil samples, illustrating host choice and longevity of the V. longisporum microsclerotia. This study demonstrates the applicability of new molecular diagnostic tools that are important for growers of variable crops.
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