Begomovirus disease complex: emerging threat to vegetable production systems of West and Central Africa

Vegetables play a major role in the livelihoods of the rural poor in Africa. Among major constraints to vegetable production worldwide are diseases caused by a group of viruses belonging to the genus Begomovirus, family Geminiviridae. Begomoviruses are plant-infecting viruses, which are transmitted by the whitefly vector Bemisia tabaci and have been known to cause extreme yield reduction in a number of economically important vegetables around the world. Several begomoviruses have been detected infecting vegetable crops in West and Central Africa (WCA). Small single stranded circular molecules, alphasatellites and betasatellites, which are about half the size of their helper begomovirus genome, have also been detected in plants infected by begomoviruses. In WCA, B. tabaci has been associated with suspected begomovirus infections in many vegetable crops and weed species. Sequencing of viral genomes from crops such as okra resulted in the identification of two previously known begomovirus species (Cotton leaf curl Gezira virus and Okra yellow crinkle virus) as well as a new recombinant begomovirus species (Okra leaf curl Cameroon virus), a betasatellite (Cotton leaf curl Gezira betasatellite) and new alphasatellites. Tomato and pepper plants with leaf curling were shown to contain isolates of new begomoviruses, collectively referred to as West African tomato-infecting begomoviruses (WATIBs), new alphasatellites and betasatellites. To study the potential of weeds serving as begomovirus reservoirs, begomoviruses and satellites in the weed Ageratum conyzoides were characterized. Sequence analyses showed that they were infected by isolates of a new begomovirus (Ageratum leaf curl Cameroon virus) that belong to the WATIBs group, a new betasatellite (Ageratum leaf curl Cameroon betasatellite), an alphasatellite and two types of defective recombinants between a begomovirus and an alphasatellite. Putative recombinations were detected in begomovirus genomes for all four plant species studied, indicating that recombination is an important mechanism for their evolution. A close relationship between the begomoviruses infecting pepper and tomato and A. conyzoides and the detection of the same alphasatellite in them support the idea that weeds are important reservoirs for begomoviruses and their satellites. With this high diversity, recombination potential and transmission by B. tabaci, begomoviruses and ssDNA satellites pose a serious threat to crop production in West and Central Africa

Symptom evolution following the emergence of maize streak virus

For pathogens infecting single host species evolutionary trade-offs have previously been demonstrated between pathogen-induced mortality rates and transmission rates. It remains unclear, however, how such trade-offs impact sub-lethal pathogen-inflicted damage, and whether these trade-offs even occur in broad host-range pathogens. Here, we examine changes over the past 110 years in symptoms induced in maize by the broad host-range pathogen, maize streak virus (MSV). Specifically, we use the quantified symptom intensities of cloned MSV isolates in differentially resistant maize genotypes to phylogenetically infer ancestral symptom intensities and check for phylogenetic signal associated with these symptom intensities. We show that whereas symptoms reflecting harm to the host have remained constant or decreased, there has been an increase in how extensively MSV colonizes the cells upon which transmission vectors feed

Mixed infection by two West African tomatoinfecting begomoviruses and ageratum leaf curl Cameroon betasatellite in tomato in Cameroon

Published online: 10 July 2014Begomovirus isolates ToF3B2 and ToF3B17and betasatellite isolate SatBToF3 were obtained from thesame infected tomato plant showing begomovirus diseasesymptoms in Fontem, Cameroon. The full-length nucleotidesequences of ToF3B2, ToF3B17 and SatBToF3 werecloned and sequenced and were determined to be 2,797 nt,2,794 and 1,373 nt long respectively. When compared withother begomovirus and betasatellite sequences, ToF3B2was 93.5 % identical to Tomato leaf curl Togo virus,ToF3B17 was 95 % identical to Tomato leaf curl Cameroonvirus and SatBToF3 was 92 % identical to Ageratumleaf curl Cameroon betasatellite (ALCCMB), respectively.The identification of ALCCMB in Ageratum and now intomato strongly suggests Ageratum may be an alternativehost to these viruses and that ALCCMB is non host specificand may cause severe diseases when transmitted to othercrops

Erasmus Mundus Master emPLANT: applied plant biotechnology

European Biotechnology Congress -- APR 11-13, 2019 -- Valencia, SPAINGOTOR, Alicia AYERDI/0000-0001-6725-3334WOS: 000491118400026[No abstract available]Erasmus + Programme of the European Union [586618-EPP-1-2017-1-FR-EPPKA1-JMD-MOB]emPLANT is co-funded by the Erasmus + Programme of the European Union grant EMJMD- in Plant Breeding number 586618-EPP-1-2017-1-FR-EPPKA1-JMD-MOB

Genetic diversity of wheat dwarf virus

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Detection of Tomato yellow leaf curl virus in imported tomato fruit in northern Europe

Article first published online: 25 FEB 2014. Author(Leke, W.) present address is IITA indicated on the publication.Imported tomato fruits infected withTomato yellow leaf curl virus(TYLCV) were identified on the market in northernEurope using paper-based FTA Classic Cards (Whatman), polymerase chain reaction (PCR) and partial DNA sequenceanalysis. Trade tomatoes originating from southern Europe, Africa and the Middle East were sampled in Estonia andSweden, and tested for infection with begomoviruses. Out of 100 batches analysed with five fruits sampled in eachbatch (58 batches from Estonia and 42 from Sweden), 20 batches were positive (16 from Estonia and four fromSweden). Rolling circle amplification (RCA) and full-length genome sequence analysis of one isolate collected in Estoniaand one isolate in Sweden, revealed highest nucleotide sequence identity at 99% to TYLCV-IL for the Estonian isolateand at 97% to TYLCV-Mld for the Swedish isolate. In this study, TYLCV was identified for the first time in importedtomato fruits on the market in northern Europe. FTA cards proved to be an effective means to collect, extract andstore begomovirus DNA from tomato fruits and the subsequent molecular analysisImported tomato fruits infected withTomato yellow leaf curl virus(TYLCV) were identified on the market in northernEurope using paper-based FTA Classic Cards (Whatman), polymerase chain reaction (PCR) and partial DNA sequenceanalysis. Trade tomatoes originating from southern Europe, Africa and the Middle East were sampled in Estonia andSweden, and tested for infection with begomoviruses. Out of 100 batches analysed with five fruits sampled in eachbatch (58 batches from Estonia and 42 from Sweden), 20 batches were positive (16 from Estonia and four fromSweden). Rolling circle amplification (RCA) and full-length genome sequence analysis of one isolate collected in Estoniaand one isolate in Sweden, revealed highest nucleotide sequence identity at 99% to TYLCV-IL for the Estonian isolateand at 97% to TYLCV-Mld for the Swedish isolate. In this study, TYLCV was identified for the first time in importedtomato fruits on the market in northern Europe. FTA cards proved to be an effective means to collect, extract andstore begomovirus DNA from tomato fruits and the subsequent molecular analysis

Molecular characterization of two previously undescribed begomovirus-associated alphasatellite molecules infecting malvaceous species in Cameroon

Two begomovirus-associated alphasatellites were isolated from okra and a malvastrum plant (Malvaceae) in Cameroon. The complete nucleotide sequences of the okra- and malvastrum-infecting alphasatellites were 1375 and 1416-1418 nucleotides, respectively, and both exhibited features characteristic of other alphasatellites. Based on pairwise sequence comparisons, these previously undescribed alphasatellites are members of distinct species in the genera Colecusatellite and Gosmusatellite and have been tentatively named "pepper yellow vein Mali alphasatellite" and "cotton leaf curl Gezira alphasatellite3", respectively. Taken together with previous studies, alphasatellites endemic to Cameroon appear to be more diverse and infect plants of many more species and families than currently recognized.12 month embargo; published online: 9 January 2020This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

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

Item does not contain fulltextCotton 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 infectivity and symptoms in Nicotiana benthamiana were investigated. Each mutation introduced a premature stop codon which would lead to premature termination of translation of the gene. Mutation of the CP gene abolished infectivity. However, transient expression of the CLCuKoV CP gene under the control of the Cauliflower mosaic virus 35S promoter (35S-Ko(CP)), at the point of inoculation, led to a small number of plants in which viral DNA could be detected by PCR in tissues distal to the inoculation site. Mutations of the V2, C2 and C4 genes reduced infectivity. The V2 and C2 mutants did not induce symptoms, whereas the C4 mutation was associated with attenuated symptoms. Infections of plants with the C4 mutant were associated with viral DNA levels equivalent to the wild-type virus, whereas viral DNA levels for the V2 mutant were low, detectable by Southern blot hybridisation, and for the C2 mutant were detectable only by PCR. Significantly, transient expression of the CLCuKoV C2 gene at the point of inoculation, raised virus DNA levels in tissues distal to the inoculation site such that they could be detected by Southern hybridisation, although they remained at well below the levels seen for the wild-type virus, but reduced the infectivity of the virus. These findings are consistent with earlier mutation studies of monopartite begomoviruses and our present knowledge concerning the functions of the four genes suggesting that the CP 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 suggest that the V2, C2 and C4 may be pathogenicity determinants. Additionally the effects of the mutations of CLCuKoV genes on infections of the virus in the presence of its cognate betasatellite, Cotton leaf curl Multan betasatellite (CLCuMuB), were investigated. Mutation of the C4 gene had no effect on maintenance of the betasatellite, although the betasatellite enhanced symptoms. Inoculation of the C2 mutant with CLCuMuB raised the infectivity of the virus to near wild-type levels, although the numbers of plants in which the betasatellite was maintained was reduced, in comparison to wild-type virus infections with CLCuMuB, and viral DNA could not be detected by Southern hybridisation. Transient expression of the C2 gene at the point of inoculation raised virus DNA levels in tissues distal to the inoculation site but also reduced 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 of plants was the satellite maintained and infections were non-symptomatic. Although inoculation of the CP mutant with CLCuMuB did not restore infectivity, co-inoculation with 35S-Ko(CP) increased the number of plants in which the virus could be detected, in comparison to plants inoculated with the mutant and 35S-Ko(CP), and also resulted in two plants (out of 15 inoculated) in which the betasatellite could be detected by PCR. This indicates that the V2, C2 and almost certainly the CP are important for the maintenance of betasatellites by monopartite begomoviruses. The significance of these findings is discussed

Genetic diversity of Wheat dwarf mastrevirus

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