Leke et al. Agriculture & Food Security (2015) 4:1
DOI 10.1186/s40066-014-0020-2
REVIEW
Open Access
Begomovirus disease complex: emerging threat
to vegetable production systems of West and
Central Africa
Walter N Leke1,2*, Djana B Mignouna1, Judith K Brown3 and Anders Kvarnheden4
Abstract
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.
Keywords: Begomoviruses, Okra leaf curl disease, Whitefly, Tomato leaf curl disease, West and Central Africa,
Viral satellites
* Correspondence: wnleke@yahoo.com
1
International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo road,
Ibadan, Nigeria
2
Institute of Agricultural Research for Development (IRAD), P.O. Box 2123,
Messa, Yaoundé, Cameroon
Full list of author information is available at the end of the article
© 2015 Leke et al.; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain
Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,
unless otherwise stated.
Leke et al. Agriculture & Food Security (2015) 4:1
Introduction
The population size of West and Central Africa (WCA)
is approximately 350 million people with about 80% depending on agriculture for their livelihoods. Vegetables
play an essential role in the diet, health, and livelihoods
of the rural poor in WCA. A survey conducted by the
Natural Resources Institute in Cameroon and Uganda
provides evidence that vegetables offer a significant opportunity for poor people to earn a leaving [1]. Among
the major constraints to vegetable crop production is a
group of viruses belonging to the family Geminiviridae.
Geminiviruses are arguably the most damaging plant viruses worldwide and pose a severe threat to global food
security. They are abundant in tropical and subtropical
environments, where insects that transmit these viruses
are abundant. Although geminiviruses have been identified as plant pathogens for many years [2,3], the advent
of modern cropping practices has made these viruses
more widespread, particularly to monoculture vegetable
Page 2 of 14
crop farms [4,5]. Geminiviruses are divided into seven
genera—Becurtovirus, Begomovirus, Eragrovirus, Mastrevirus, Curtovirus, Topocuvirus, and Turncurtovirus—
based on genome organization, nucleotide sequence
similarities, and biological properties [6]. The genome of
viruses in the genus Begomovirus consists of either two
genomic components, bipartite (known as DNA-A and
DNA-B) of about equal size (~2.8 kb; example East African
cassava mosaic Cameroon virus, EACMCV) (Figure 1A)
or a single component, monopartite, homologous to the
DNA-A component of bipartite viruses (example Tomato
leaf curl Cameroon virus, ToLCCMV) (Figure 1B) [7,8].
Begomoviruses cause many diseases of dicotyledonous
crops and wild plants. The symptoms typically consist of
leaf curling, mosaic, vein yellowing, or more generalized
leaf yellowing, often accompanied by stunting of plant
growth (Figure 2). Some of these diseases are among
the world’s most economically important plant virus
diseases, for example, mosaic diseases of cassava in
Figure 1 Genome organization of the bipartite (A) and monopartite (B) members of the genus Begomovirus, alphasatellites (C) and
betasatellites (D). Arrows represent open reading frames. V1/(AV1) coat protein gene, V2/AV2 precoat prorein gene, C1 (AC1) replication initiator
protein gene, C2 (AC2) transcription activator protein gene, C3 (AC3) replication enhancer protein gene, C4 (AC4) symptom determinant protein
gene, BV1 nuclear shuttle protein gene, and BC1 movement protein gene. A-rich: adenosine-rich region of the genome; βC1: the gene encoding
the betaC1 protein; SCR: satellite-conserved region. Imagines are not to the scale.
Leke et al. Agriculture & Food Security (2015) 4:1
Page 3 of 14
Genome organization of monopartite begomoviruses
The genome of monopartite begomoviruses contains
six open reading frames (ORFs). The coat protein gene
(CP or V1), and V2, are expressed from the viral sense
strand, and C1 (replication-associated (activator) protein
(Rep)), C2, C3, and C4, are expressed from the complementary strand [16] (Figure 1B).
DNA satellite molecules associated with monopartite
begomoviruses
Figure 2 Symptoms in begomovirus infected crops and weeds
in West and Central Africa. (A) Ageratum conyzoides; (B) Asystasia
gangetica; (C) Emilia cocinea; (D) Okra, Abelmoschus esculentus;
(E) Pepper, Capsicum annuum; (F) Tomato, Solanum lycopersicum;
(G) Clerodendrum umbellatum; (H) Malvastrum spp.; and (I)
Sida corymbosa.
Sub-Saharan Africa probably cause annual yield losses
exceeding $2 billion in value of a staple food for millions of poor people [9].
Genome organization of bipartite begomoviruses
Except for a short sequence of ~200 nts, referred to as
the ‘common region’ (CR), the DNA-A and DNA-B
components share no sequence similarity. The CR contains the nonanucleotide TAATATTAC sequence, where
rolling circle replication is initiated, and that is conserved among members of the family Geminiviridae
[10-12]. Both genomic components contain proteincoding sequences on the viral sense strand and on the
complementary strand. Six genes seem to be universally
present in all bipartite begomoviruses. The DNA-A
component contains one gene (AV1) on the viral sense
strand and three genes (AC1, AC2, AC3) on the complementary strand for the New World (NW) bipartite begomoviruses [13] and an additional gene AV2 in the viral
sense strand and C4 on the complementary strand for
the Old World (OW) bipartite begomoviruses [14]. The
sense and complementary strands of the DNA-B component each contains one gene, BV1 and BC1, respectively
[15] (Figure 1A).
Satellites are defined as viruses or nucleic acids that depend on the helper virus for their replication but lack
extensive nucleotide sequence identity to the helper
virus and are dispensable for its proliferation [17]. Satellite viruses encode a structural protein, which encapsidates its own nucleic acid, while satellite nucleic acids
rely on the helper virus structural protein for encapsidation and do not necessarily encode additional nonstructural proteins. A third type of agent, referred to as
satellite-like nucleic acid, also depends on the helper
virus for its replication but provides a function that is
necessary for the biological success of the helper virus
and is therefore considered as part of the helper virus
genome [18]. The first satellite RNA was identified in
1969 in association with the nepovirus Tobacco ringspot
virus [18], and since then, a large number of satellite
RNAs, associated with several groups of plant viruses,
have been reported [17], with the majority of the satellites interfering with the replication of the helper viruses,
resulting in attenuated symptoms. Some satellites exacerbate disease symptoms induced by the helper virus
or produce novel symptoms which are usually not associated with the helper virus infections [19].
The first begomovirus satellite DNA to be discovered
was found to be associated with the monopartite begomovirus Tomato leaf curl virus (ToLCV) from Australia
[20]. This 682 nt circular ssDNA depends on ToLCV for
its replication and encapsidation, but its replication can
also be supported by other begomoviruses. It has no
proven effects on the viral replication or on symptoms
caused by ToLCV. It has no extensive ORFs and has little sequence similarity to its helper virus (ToLCV) except for the nonanucleotide TAATATTAC sequence
presents in the stem loop of all geminiviruses [21]. Failure to reproduce yellow vein symptoms in Ageratum
conyzoides (goat weed) by re-introduction of Ageratum
yellow vein virus (AYVV) [22,23], suggested that another
factor was required to restore pathogenicity in the natural host. In a search for additional viral components, a
number of small circular recombinant components, each
containing the AYVV origin of replication together with
sequences of unknown origin, were isolated from infected goat weed [24]. Similar recombinants were also
identified for the begomoviruses associated with cotton
Leke et al. Agriculture & Food Security (2015) 4:1
leaf curl disease (CLCuD) [25-27]. The significance of
the unidentified sequences within the recombinants was
not appreciated at the time, but they were to provide a
vital clue in the discovery of a new class of satellites. As
was observed for AYVV, the cloned genomic component
of cotton leaf curl virus (renamed Cotton leaf curl Multan virus, CLCuMV) failed to induce typical CLCuD
symptoms, suggesting the presence of another factor
[26], whose search resulted in the isolation of a small
circular ssDNA molecule, referred to as DNA-1 [28],
which is a representative of a new class of components
associated with monopartite begomoviruses [29].
Recently, many monopartite begomoviruses have been
identified that associate with a type of satellite molecule
referred to as betasatellite, composed of ssDNA, ~1.3 kb
in size and approximately half the size of the helper
begomoviruses (Figure 1D). Many of the betasatellites
are required for typical disease symptom development
[22,27,30-33]. Despite their recent discovery, betasatellites
may have existed for many centuries, e.g., Eupatorium yellow vein betasatellite.
(EpYVB) in association with Eupatorium yellow vein
virus (EpYVV) have been demonstrated to cause eupatorium yellow vein disease (EpYVD), which was described
about 1250 years ago [2]. All betasatellites require a helper
begomovirus for replication, local and systemic spread,
and whitefly vector-mediated transmission, and some have
been shown to modulate symptom severity [33]. To further show the role that betasatellites play in begomoviral
disease etiology, the βC1 (Figure 1D) has in one instance
been shown to be responsible for the suppression of jasmonic acid signaling involved in at least one gene silencing pathway [34]. The transgenic plants of Arabidopsis
thaliana expressing βC1 of Tomato yellow leaf curl China
betasatellite (TYLCCNB) were shown to develop disease
symptoms like that observed in begomovirus-infected
tobacco plants, in that plants exhibited upward leaf
curling, foliar enations, and sterile flowers [35]. All betasatellite molecules contain one ORF (βC1) (Figure 1D), an
A-rich region ~240 nts long and a satellite-conserved region (SCR), of ~220 nts. Apart from the nonanucleotide
sequence, betasatellites do not share any significant sequence similarity with the helper begomoviruses.
The begomovirus/betasatellite complexes are often associated with a second type of circular ssDNA satellite, initially referred to as DNA-1 [28,29,36,37], but now called
alphasatellites [38]. Alphasatellites encode a single protein
that shares high nt identity with the Rep (Figure 1C), a
rolling-circle replication initiator protein encoded by
viruses in the genus Nanovirus, family Nanoviridae that
also have a genome of circular ssDNA [39]. Consequently,
alphasatellites are capable of autonomous replication
but require a helper begomovirus for spread in plants
and for whitefly vector transmission. In addition to
Page 4 of 14
Rep, alphasatellites also have an A-rich region, ~200
nts long, downstream of the Rep-encoding region. Recently, it has been demonstrated that the alphasatellite associated with Tobacco curly shoot virus (TbCSV) can be
used as a virus-induced gene silencing (VIGS) vector [40].
In contrast to betasatellites, alphasatellites possess in their
stem loop the nonanucleotide sequence TAGTATTAC
which is also found in the stem loop of viruses in the family Nanoviridae. Alphasatellites can affect both begomovirus titer and symptom development in host plants
[36,41]. Initially it was thought that satellite molecules
were limited to the OW, but recently, alphasatellites have
been found associated with NW begomoviruses [42,43],
thus expanding the geographical distribution of satellite
molecules associated with begomoviruses.
Diversity and distribution of begomoviruses and ssDNA
satellites in West and Central Africa
Until recently, knowledge on the prevalence and impact
of begomoviruses in West and Central Africa has been
rather scanty. Initially, information on the existence of
begomoviruses infecting crops in the region was based
on serology and hybridization, with emphasis on cassava
mosaic disease (CMD), okra leaf curl disease (OLCD)
and tomato leaf curl disease (ToLCD) [44-48]. With the
advent of more advanced molecular techniques in the
study of begomoviruses, such as polymerase chain reaction (PCR), rolling cycle amplification (RCA)/restriction
fragment length polymorphism (RFLP), and sequencing,
the situation has greatly improved, leading to the identification of previously unknown begomovirus/satellite
complexes infecting tomato, okra and pepper such as
Tomato leaf curl Cameroon virus (ToLCCMV), Tomato
leaf curl Nigeria virus (ToLCNGV), Tomato leaf curl
Ghana virus (ToLCGHV), Tomato leaf curl Kumasi virus
(ToLCKuV), and Tomato leaf curl Togo virus (ToLCTGV),
which could collectively be termed the West African
tomato-infecting begomoviruses (WATIBs) (Figure 3). Beside the WATIBs, others such as Tomato yellow leaf
curl Mali virus (TYLCMLV), Pepper yellow vein Mali
virus (PepYVMLV), and Tomato leaf curl Mali virus
(ToLCMLV) have been identified infecting tomato
and pepper in the region [49-57] (Figure 3 arrows).
Apart from the pepper and tomato-infecting begomoviruses, others such as Cotton leaf curl Gezira virus
(CLCuGeV), Okra leaf curl Cameroon virus (OLCuCMV),
and Okra yellow crinkle virus (OYCrV) have been
identified infecting okra in West and Central Africa
[49,52,56,58] (Figure 3). Putative recombination events
were detected in begomovirus genomes for all three
plant species studied, indicating that recombination is an
important mechanism for their evolution. The concentration of previous research in the region on ACMD, OLCD,
and ToLCD, clearly underscores the importance of these
Leke et al. Agriculture & Food Security (2015) 4:1
Page 5 of 14
Figure 3 Neighbor-joining phylogenetic analysis. Using MEGA 4.0 of the complete genome of isolates of the West African tomato-infecting
begomoviruses (WATIBs) and other begomovirus isolates from the NCBI GenBank. Arrows indicate other begomoviruses identified in West and
Central Africa other than the WATIBs. Horizontal lines are in proportion to the number of nucleotide substitutions per site. Numbers represent
percent bootstrap values out of 2,000 replicates. The GenBank accession numbers of the nucleotide sequences are indicated. The abbreviations
are according to Brown et al. [59].
diseases, which are still being somewhat neglected due to
the lack of trained personnel in advanced molecular techniques and adequate funding for fundamental research.
Previously, information on the existence and diversity
of DNA satellite molecules associated with monopartite
begomoviruses has been mainly available for Asia [60-63].
The presence of DNA satellites in Africa was first shown
in a survey for alphasatellites in samples from Asia and
Africa, where they were found in different plants from
both Egypt and Kenya [29] (Figure 4). Recently, one betasatellite, Cotton leaf curl Gezira betasatellite (CLCuGB),
initially identified in the Nile basin, has been identified
in West and Central Africa, associated with diseased
okra and tomato [52,55,56,58,64] (Figure 5). Two new
betasatellites, Ageratum leaf curl Cameroon betasatellite (ALCCMB) and Tomato leaf curl Togo betasatellite (ToLCTGB), have been identified infecting A.
conyzoides and tomato in Cameroon and Togo, respectively [51,53,65] (Figure 5). Also, new types of alphasatellites,
Ageratum leaf curl Cameroon alphasatellite (ALCCMA),
Tomato leaf curl Cameroon alphasatellite (ToLCCMA),
Okra leaf curl Mali alphasatellite (OLCuMLA), Okra leaf
curl Burkina Faso alphasatellite (OLCuBFA), and Okra yellow crinkle alphasatellite (OYCrA), have been identified
infecting A. conyzoides, okra, and tomato [50-53,56,58] in
West Africa and the lone Central African state, Cameroon.
In West and Central Africa, Bemisia tabaci has been
associated with suspected begomovirus infections in
many crop species, including cassava, bean, cotton, eggplant, pepper, squash, tomato, okra, and watermelon as well
as weeds of the genera Ageratum, Asystasia, Clerodendrum,
Emilia, and Malvastrum. This observation was based on
the consistent presence of B. tabaci on plants exhibiting
characteristic symptoms of begomovirus infection (leaf
Leke et al. Agriculture & Food Security (2015) 4:1
Page 6 of 14
Figure 4 Neighbor-joining analysis. Using MEGA 4.0 of the complete genome of isolates of the West and Central African alphasatellites and
other alphasatellite isolates from GenBank. Horizontal lines are in proportion to the number of nucleotide substitutions per site. Numbers represent
percent bootstrap values out of 2,000 replicates. The GenBank accession numbers of the nucleotide sequences of alphasatellites are indicated.
The abbreviations are according to Briddon et al. [66].
curling and distortion, green or yellow foliar mosaic, stunting, reduced yields). Thus, there is a pressing need for additional information on the diversity and distribution of
begomoviruses and satellites in vegetable crops and/or dicotyledonous weeds, which likely serve as virus reservoirs.
This review thus presents a tip of the iceberg on the diversity of begomoviruses and associated satellite DNAs infecting vegetable crops in West and Central Africa.
Economic impact of begomoviruses/ssDNA satellites on
vegetable production systems and food security in West
and Central Africa
Vegetables have been grown and utilized traditionally in
most if not all of the African countries for home consumption and domestic markets. Of late, vegetable production
has shifted from subsistence to include export markets
representing an important driver for growth due to employment opportunities in production, processing, and
trade. Vegetables have proven to be important rain-fed
crops [67], and several advantages and potentials of vegetable production are still not being fully exploited.
With the rapid urbanization and population growth,
market-oriented vegetable production is increasing in periurban areas and has considerable potential for earning
foreign exchange, thus generating employment opportunities and income, improving food security, alleviating poverty, and enhancing development in the region. Vegetables
account for an estimated 40% of the market sales of products in the region [68]. Vegetables are mainly grown and
traded by women in domestic markets with substantial
regional market linkages [68]. Increased and sustained
growth in this sector will translate into more income for
women and associated benefits for household nutrition
and food security, health, and educational status of children [68].
Based on the Food and Agriculture Organization (FAO)
statistics, annual production of okra, pepper and tomato
in WCA fluctuates over the years [68]. The region accounts for more than 75% of okra produced in Africa and
West Africa is the largest okra producer [69] (Figure 6).
Okra production has increased moderately in Central
Africa from 9.4 thousand tons in the year 2000 to 23
thousand tons in 2004. From 2004, okra experienced
a decrease of 61% before continuing its slow increase
over years. Pepper and tomato production was more
important in West Africa than in Central Africa. Pepper
and tomato production in WCA has increased moderately
over the years from 2000 to 2012. Pepper production in
Leke et al. Agriculture & Food Security (2015) 4:1
Page 7 of 14
Figure 5 Neighbor-joining phylogenetic analysis. Using MEGA 4.0 of the complete genome of isolates of the West and Central African
betasatellites and other betasatellite isolates from the NCBI GenBank. Horizontal lines are in proportion to the number of nucleotide substitutions
per site. Numbers represent at the branch nodes are percent bootstrap values out of 2,000 replicates. The abbreviations are according to Briddon
et al. [66].
West Africa increased from 2000 to 2008 before decreasing from 2009 up to 2013 while in Central Africa tomato
production growth started in 2009 (Figure 6). Yields of
okra, tomato and pepper in WCA as depicted in Figure 6
are lagging far behind those worldwide. In fact, much of
the increase in world vegetable production is attributed
mainly to yield improvements and their yield is still way
below their maximum potential affecting the production
which experienced rising infections by begomoviruses and
associated ssDNA satellites [70,71]. As early as the 1950s,
begomoviruses have been reported to cause important
losses in vegetables ranging from 20% up to 100% [70-72].
Potential for control
The sustainable management of begomovirus diseases in
West and Central Africa will depend on the use of an integrated pest management (IPM) approach. The use of
resistant/tolerant cultivars is an important part of disease
Leke et al. Agriculture & Food Security (2015) 4:1
Page 8 of 14
Area of Okra Harvested (Thousand Ha)
Area of Pepper Harvested (Thousand Ha)
600
1000
Area of Tomatoes Harvested (Thousand Ha)
4000
400
500
2000
200
0
0
0
Central Africa
Western Africa
Africa
World
Central Africa
Okra Production (Thousand Tonne)
Western Africa
Africa
World
Central Africa
Pepper Production (Thousand Tonne)
Western Africa
Africa
World
Tomatoes Production (Thousand Tonne)
400
100000
5000
200
0
0
0
Central Africa
Western Africa
Africa
World
Central Africa
Western Africa
Africa
World
Central Africa
Pepper Yield (Tonne/Ha)
Okra Yield (Tonne/Ha)
8
Western Africa
Africa
World
Tomatoes Yield (Tonne/Ha)
3
30
6
2
20
4
2
0
Central Africa
Western Africa
Africa
World
1
10
0
0
Central Africa
Western Africa
Africa
World
Central Africa
Western Africa
Africa
World
Figure 6 Production and yield trends for okra, pepper, and tomato in West and Central Africa (WCA).
control as well as the use of different methods for limiting
begomovirus spread by the whitefly vector. However, the
breeding for resistance to begomoviruses is complicated
by their high diversity, ability to form new genotypes by
recombination, and the occurrence of DNA satellites.
Resistance
The local tomato cultivars in West and Central Africa as
well as old cultivars such as Moneymaker and Roma are
susceptible to important diseases, including tomato leaf
curl/tomato yellow leaf curl (ToLCD/TYLCD) [73,74].
Recently, tomato cultivars with resistance to begomoviruses have been widely adopted throughout the world.
They are not immune to infection but may give an acceptable yield even when infected [75,76]. The resistance
has been crossed into tomato from wild relatives [77].
Common resistance genes in tomato are the allelic genes
Ty-1 and Ty-3, which originate from accessions of Solanum chilense. These resistance genes have been cloned
and found to encode an RNA-dependent RNA polymerase, and the resistance involves increased cytosine methylation of the viral genome [75]. Field trials carried out in
Mali under a high infection pressure of begomoviruses
showed that breeding lines of tomato with the resistance
genes Ty-1 and Ty-3 produced a higher yield than the
commercial susceptible cultivars [78]. In a recent survey,
41 tomato varieties from different sources were screened
in the field in Senegal for resistance to TYLCD [74]. The
trial included also commercial varieties with resistance
or tolerance to TYLCD. A substantial variability was
observed with a disease incidence from 0% to 100% and a
severity of 0% to 89%. Twelve genotypes were identified as
having a high level of resistance and being suitable for
cultivation under a high disease pressure. Similar studies
were carried out simultaneously in Benin, Burkina Faso,
Ghana, Mali, and Togo, using the same varieties, but the
varieties turned out to perform differently in the different
countries [74]. It will be important to identify the factors
causing this difference in resistance, and one factor would
likely be the viruses. The screens were completely based
on symptoms, and there could have been infection with
different begomoviruses and DNA satellites as well as with
other viruses. The resistance conferred by the gene Ty-1
has, for example, been compromised when plants become
infected with multiple RNA viruses [75]. Also in pepper,
there are variations in the susceptibility to begomovirus
Leke et al. Agriculture & Food Security (2015) 4:1
infections. In Nigeria, moderate resistance in four pepper
cultivars has been identified [79]. In addition to the
conventional breeding, different transgenic approaches
for achieving resistance or tolerance have been tested
against begomoviruses infecting tomato and pepper [80-82]
and this may be a way forward for obtaining durable
resistance.
In West and Central Africa, leaf curl disease is regarded
as the most important biotic stress for okra, and there is a
lack of viral resistance/tolerance [58,83]. However, okra
has been regarded as a crop of minor importance, and the
breeding efforts for okra in the region have been limited.
In India and Bangladesh, screens have revealed resistance and tolerance to be present in some cultivated varieties and wild species of okra against yellow vein mosaic
disease (OYVMD), which is also caused by begomoviruses
[84]. The genetic material identified in these screens may
be of value also for adoption in breeding programs for
resistance/tolerance to begomoviruses present in Africa.
Screens of genetic material in the region will probably also
reveal useful breeding material [58,83]. In a field trial in
Burkina Faso with four accessions of a local okra cultivar
and four improved commercial okra cultivars, the incidence of OLCD was higher in the local cultivar compared
to the commercial cultivars [58]. The difference was suggested to be related to a possible resistance in the commercial cultivars to the whitefly vector.
Whitefly vector management
Insecticides are frequently used to control B. tabaci in
different crops, and it is often the main way of control.
However, besides the detrimental effects on human
health and the environment, the repeated use of the
same types of insecticides will lead to the selection for
resistance in the insect and may also reduce the numbers of beneficial insects which are natural enemies of
whiteflies. Cotton is heavily sprayed for management of
insects, and this practice also affects the control of
whiteflies in vegetable crops. Tests on B. tabaci populations from cotton fields in Burkina Faso showed that
they were resistant to the recommended doses of several
chemicals, suggesting that selection for resistance was
likely to occur [85]. The systematic use in cotton of pyrethroids, organophosphates and neonicotinoids has
probably lead to the observed reduction in susceptibility
or even resistance in populations of B. tabaci in Benin,
Togo and Burkina Faso [86]. Transgenic cotton varieties
with Bacillus thuringiensis (Bt) resistance against lepidopteran larvae have been introduced into Burkina Faso.
The cultivation of these varieties involves less insecticide
with a reduction in the amount of chemicals used. However, neonicotinoids are applied to the Bt cotton for control of whiteflies, and this leads to the selection of the
resistant Q-biotype of B. tabaci [86,87]. Therefore, it is
Page 9 of 14
important that insecticides are managed in a sustainable
manner and in combination with other control methods.
Agricultural practices
In West and Central Africa, tomato is produced all around
the year, which aggravates the problem with diseases.
ToLCD/TYLCD is a large constraint, especially during the
dry season, when the whitefly populations are highest
[54]. The implementation of host-free periods has been a
successful way for control of begomovirus infections of tomato, for example, in Israel and the Dominican Republic
[88,89]. A host-free period with no tomato or solanaceous
crop is also used in some areas of West Africa with a
high incidence of ToLCD/TYLCD [78,90]. The establishment of such a period can be difficult to implement
since our knowledge of alternative hosts of begomoviruses
is very limited and may lead to an associated reduction in
farmers’ income because they will be out of production
during this period. Still, in Mali, a host-free period of
2 months has been reported to be successful for managing
begomovirus infections of tomato [90]. As part of an IPM
approach, other agricultural practices for management of
ToLCD/TYLCD and other diseases caused by begomoviruses include eradication of source plants, cultivation of
bait plants, reflective mulches and inclusion of physical
barriers, and use of virus-free transplants [89-92]. In
Nigeria, early planting of pepper or tomato has been
found to reduce disease incidence [79]. Practices suggested
for vegetable production in tropical Africa have also
been intercropping to divert whiteflies or changed sowing
times to avoid periods of peaks with pest populations [93].
The best-suited practices for control of begomovirus infections will depend on the local conditions, and different
types of management methods will have to be tested.
Virus reservoirs
Besides the crop plants, the begomoviruses have weeds
and wild plants as hosts. For complete understanding of
the epidemiology and for developing appropriate control
measures, the identification of alternative hosts is an important aspect of the study which has been somewhat
neglected in the past. Presently, the begomovirus reservoirs remain largely unknown. A recent study showed
that the common weed A. conyzoides in Cameroon is
host to a complex consisting of Ageratum leaf curl
Cameroon virus (ALCCMV), Ageratum leaf curl betasatellite (ALCCMB), and Ageratum leaf curl Cameroon
alphasatellite (ALCCMA) [51]. Sequence analyses revealed that the begomovirus was most closely related to
a group of tomato-infecting begomoviruses from West
Africa suggesting that these viruses may have common
hosts. The betasatellite of A. conyzoides has now also
been detected in tomato [53]. Of late, a new betasatellite,
Tomato leaf curl Togo betasatellite (ToLCTGB), has
Leke et al. Agriculture & Food Security (2015) 4:1
been identified infecting tomato in Togo and with its
closest relative being ALCCMB [65]. That uncultivated
(wild) hosts serve as reservoirs for these viruses are
further demonstrated by the recent identification of
Lamium amplexicaule (family Lamiaceae) as a host of
Tomato yellow leaf curl virus (TYLCV) in Korea [94].
These results further stress the urgent need for the search
of alternative hosts of begomoviruses and associated
ssDNA satellites infecting vegetables in West and Central
Africa.
Page 10 of 14
Togo, the B-like, silvering and sub-Saharan African nonsilvering types predominated. In contrast, Q-like haplotypes were most widespread in Burkina Faso. In some
instances the B-like silvering and Q-like haplotypes overlapped in host and location. In cassava plantings, an
invasive-like non-B/non-Q type that also differs genetically from the sub-Saharan non-silvering type found
in the above three countries, has been reported accompanying the rapidly spreading CMD, as it appears
to be spreading toward and/or into Cameroon and neighboring countries [108].
Whitefly B. tabaci vector: biological and genetic
variability
Diagnostic approaches for begomoviruses
The whitefly B. tabaci (Genn.) sibling species group [95]
is a group of morphologically indistinguishable haplotypes that exhibit different biological characteristics, including host range, fecundity, dispersal behavior, virus
transmission efficiency, and insecticide resistance [96].
Regardless of these and other phenotypic differences
between certain haplotypes or biotypes (well-defined)
[96-98], as a group, they are the only insect vectors of the
genus, Begomovirus, worldwide. These differences and
similarities can have important bearings on the epidemiology of begomovirus-incited diseases of vegetable, fruit,
and fiber crops [96,99], and in some instances are known
to drive begomoviral diversification [100]. The size of a
whitefly vector population is often directly associated with
begomovirus disease incidence, including a number of
outbreaks [44,47,50,52,54,56,64,101,102] and epidemics
in Africa such as the CMD pandemic in East and Central
Africa [103]. However, in some instances, extremely
high incidence has been observed even when population
levels are low.
The overall genetic diversity of the B. tabaci sibling
species group in western Africa is not well studied.
Burban et al. [104] first showed host-associated differences
among populations of B. tabaci from cassava and okra
and other host plants in Côte d'Ivoire, based on isozyme
electrophoresis and experimental host range studies. This
report was corroborated by the presence of cassava and
non-cassava haplotypes based on RAPD-PCR markers
and the internal transcribed spacer-1 (ITS-1) [105]. The
haplotype colonizing okra and other vegetable plant species appears to be polyphagous, whereas the cassavaassociated haplotype was found colonizing only cassava
plants. Gueguen et al. [106] reported three haplotypes in
Burkina Faso, a sub-Saharan type, a silvering type (B-like
clade), and a close relative of the Spanish Q (Q-like clade)
[96,98,99]. Recently, Gnankiné et al. [107] sampled B.
tabaci populations in 20 locations and seven cultivated plant hosts in Burkina Faso, Benin, and Togo
and obtained a result similar to the latter study. However, they additionally demonstrated evidence for host
and geographical affiliations, in that, in Benin and
The majority of approaches currently being used for begomovirus epidemiological and other studies rely nearly entirely on molecular methods. A number of DNA extraction
methods have been used to isolate and purify total genomic DNA from plant leaves, stems, and roots/tubers suspected to harbor begomoviruses. Most commonly, the
CTAB method of Doyle and Doyle [109] is used along
with a variety of its modifications and methods optimized
for difficult-to-handle plants [110]. Manufactured kits tailored for isolation of total genomic DNA from plants are
also widely implemented. The method of choice is best selected based on the characteristics of the plant host from
which total genomic DNA will be isolated. Plant sap from
leaves or other parts of begomoviral-infected plants have
been successfully applied to and the total genomic DNA
eluted from FTA cards. This has been shown to be effective for short-term storage of total genomic DNA that
is amenable to PCR amplification of viral DNA fragments
[111], or as template for RCA of begomoviral circular DNA
genomes [112].
PCR [113] is a widely used method for the initial amplification of begomoviral genomic fragments to demonstrate
begomoviral presence. Several broad-spectrum primer
pairs have been designed that are useful in many instances,
but thus far, no single pair of primers can be guaranteed to
amplify all begomoviruses given the extensive genomic
variation occurring within the genus worldwide. The most
common PCR target is the begomoviral coat protein (CP)
gene, or a region of it that is accessible for most isolates
using degenerate PCR primers that target the middle, or
‘core’ region, of the ORF, designated AC1048/AV494
[114,115]. Modified degenerate core CP primers have
been designed to have more broad-spectrum capabilities.
They are based on the substantially greater number of sequences available in the GenBank database by 2011 and
are available upon request (J.K. Brown, personal communication). The CP gene has proven to be an ideal target
because it is relatively highly conserved across the genus.
Two other sets of primers with broad-spectrum amplification of bipartite begomoviruses that amplify fragments
of both the DNA-A and DNA-B components have been
Leke et al. Agriculture & Food Security (2015) 4:1
reliable for PCR amplification of primarily the Western
Hemisphere begomoviruses [116] and some bipartite
viruses from the Eastern Hemisphere. A third set also
primarily useful for PCR amplification of bipartite begomoviruses targets conserved regions in the intergenic/
common region and the Rep gene [117]. Immuno-capture
PCR has also been used successfully when an antibody to the virus or related viruses is available [118].
Universal primers [119,120] have been designed to facilitate PCR amplification, cloning, and sequencing of
betasatellite molecules that associate with a number
of monopartite begomoviruses. They are particularly
prevalent among begomoviruses endemic to Africa, Asia,
and Latin America and most commonly are essential
for infectivity and/or pathogenicity of the ‘helper’ begomovirus, encoding a single multifunctional protein that
functions as a suppressor of host gene silencing among
others.
Recently, the most widely applied method for detecting
and cloning begomoviral genomes is the non-sequencespecific approach that uses bacteriophage phi29 DNA
polymerase [121,122], now referred to as RCA [123]. In
virology research, it was used first for the detection of
papillomaviruses [123]. It was first applied to begomoviruses by Inoue-Nagata et al. [124] and since has become
routinely used for begomoviral diagnostics and molecular cloning of whole viral genomes to facilitate their
characterization and enable the relatively efficient construction of infectious clones [125] and many others. RCA
also has been used to enrich for and prepare template for
begomoviral deep sequencing employing next-generation
approaches such as Illumina [126].
The most important considerations for implementing
RCA for begomovirus diagnostics are to avoid repeated
freezing and drying of the DNA so that breaks do not
occur in the circular template DNA strands [123]. The
amount of input DNA required is variable, depending on
the source of the template, but in general, only a small
amount of circular DNA (~1 ng) needs to be available for
RCA. The most common approach for confirming that
the amplification step has produced viral fragments or
genomic components of interest is to digest the multimeric high molecular weight product with one or more
diagnostic restriction enzymes that are known to or might
yield a full-length genome of a particular sized diagnostic
fragment. The endonuclease digested dsDNA products
are readily visualized by gel electrophoresis in 0.7%–1.2%
agarose, with the concentration adjusted to accommodate
the range of fragment sizes. Further processing of RCA
products including cloning, direct sequencing or additional PCR amplification is carried out. Additional PCR
amplification using virus or group-specific primers can be
carried out using the RCA product as template when the
method is used to enrich for or pre-amplify viral circular
Page 11 of 14
DNA. A number of protocols have been published, and
some of these are summarized in [123].
Conclusions
With this high diversity, recombination potential, limited
knowledge of alternative hosts, and transmission by B.
tabaci, begomoviruses and their associated ssDNA satellites pose a serious threat to crop production and thus
food security in West and Central Africa.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
WNL led the review process, did background literature studies, structured
the concepts, developed the arguments and wrote most of the manuscript.
DBM wrote the section on economic impact; JKB reviewed the manuscript,
helped design the arguments and wrote parts of the manuscript, AK
developed the section on potential for control. All authors read and
approved the final manuscript.
Authors’ information
WNL is the formal National Scientific Coordinator of annual crops research at
IRAD, was a visiting scientist at IITA, and presently a Fulbright scholar at
Delaware State University, USA, with expertise in molecular plant DNA
viruses. DBM is a regional economist at IITA. JKB is Professor, School of Plant
Sciences, University of Arizona, Tucson, Arizona, USA, with expertise in
plant-infecting DNA viruses, vector biology, and whitefly molecular
systematics. AK is a Professor of plant virology at the Department of
Plant Biology, Swedish University of Agricultural Sciences (SLU), Uppsala,
Sweden.
Acknowledgements
We sincerely thank the anonymous referees for useful comments that
strengthened this review.
Author details
1
International Institute of Tropical Agriculture (IITA), PMB 5320, Oyo road,
Ibadan, Nigeria. 2Institute of Agricultural Research for Development (IRAD),
P.O. Box 2123, Messa, Yaoundé, Cameroon. 3School of Plant Sciences,
The University of Arizona, Tucson, AZ 85721, USA. 4Department of Plant
Biology, Swedish University of Agricultural Sciences, Linnean Center for
Plant Biology, Uppsala BioCenter, P.O. Box 7080, 75007 Uppsala, Sweden.
Received: 5 August 2014 Accepted: 16 December 2014
References
1. Schippers RR. African Indigenous Vegetables. An overview of the Cultural
Species. Chatham, UK: Natural Resources Institute/ACP-EU Technical Centre
for Agricultural and Rural Cooperation; 2000. p. 214.
2. Saunders K, Bedford ID, Yahara T, Stanley J. Aetiology: the earliest recorded
plant virus disease. Nature. 2003;422:831.
3. Storey HH, Nichols RW. Studies of the mosaic diseases of cassava. Ann Appl
Biol. 1938;25:790–806.
4. Legg JP, Fauquet CM. Cassava mosaic geminiviruses in Africa. Plant Mol Biol.
2004;56:585–99.
5. Salati R, Nahkla MK, Rojas MR, Guzman P, Jaquez J, Maxwell DP, et al.
Tomato yellow leaf curl virus in the Dominican Republic: characterization of
an infectious clone, virus monitoring in whiteflies, and identification of
reservoir hosts. Phytopathology. 2002;92:487–96.
6. Varsani A, Navas-Castillo J, Moriones E, Hernández-Zepeda C, Idris A, Brown JK,
et al. Establishment of three new genera in the family Geminiviridae: Becurtovirus.
Eragrovirus and Turncurtovirus Arch Virol. 2014;159:2193–203.
7. Rojas MR, Hagen C, Lucas WJ, Gilbertson RL. Exploiting chinks in the plant’s
armor: evolution and emergence of geminiviruses. Annu Rev Plant Physiol
Plant Mol Biol. 2005;43:361–94.
8. Stanley J, Bisaro DM, Briddon RW, Brown JK, Fauquet CM, Harrison BD, et al.
Geminiviriae. In: Fauquet CM, Mayo MA, Maniloff J, Desselberger U, Ball LA,
Leke et al. Agriculture & Food Security (2015) 4:1
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
editors. VIIIth Report of the International Committee on Taxonomy of
Viruses. Virus Taxonomy. London: Elsevier/Academic Press; 2005. p. 1163–9.
Thresh JM, Otim-Nape GW, Legg JP, Fargette D. African cassava mosaic virus
disease: the magnitude of the problem. Afri J Root Tub Crops. 1997;2:13–9.
Eagle PA, Orozco BM, Hanley-Bowdoin L. A DNA-sequence required for
geminivirus replication also mediates transcriptional regulation. Plant Cell.
1994;6:1157–70.
Padidam M, Beachy RN, Fauquet CM. The role of AV2 (“precoat”) and coat
protein in viral replication and movement in tomato leaf curl geminivirus.
Virology. 1996;224:390–404.
Harrison BD, Robinson DJ. Green shoots of geminivirology. Physiol Mol
Plant Pathol. 2002;60:215–8.
Harrison BD, Robinson DJ. Natural genomic and antigenic variation in
whitefly-transmitted geminiviruses (begomoviruses). Annu Rev Phytopathol.
1999;37:369–98.
Hanley-Bowdoin L, Settlage SB, Orozco BM, Nagar S, Robertson D. Geminiviruses:
models of plant DNA replication, transcription, and cell cycle regulation. Crit Rev
Plant Sci. 1999;18:71–106.
Sanderfoot AA, Ingham DJ, Lazarowitz SG. A viral movement protein as a
nuclear shuttle. Plant Physiol. 1996;110:23–3.
Navot N, Pichersky E, Zeidian M, Zamir D, Czosnek H. Tomato yellow leaf curl
virus: a whitefly-transmitted geminivirus with a single genomic component.
Virology. 1991;185:151–61.
Mayo MA, Leibowitz MJ, Palukaitis P, Scholthof KBG, Simon AE, Stanley J,
et al. Satellites. In: Fauquet CM, Mayo MA, Maniloff J, Desselberger U,
Ball LA, editors. VIIIth Report of the International Committee on
Taxonomy of Viruses. Virus Taxonomy. London: Elsevier/Academic Press;
2005. p. 1163–9.
Schneider LR. Satellite-like particle of tobacco ringspot virus that resembles
tobacco ringspot virus. Science. 1969;166:1627–9.
Roossinck MJ, Sleat D, Palukaitis P. Satellite RNAs of plant viruses: structures
and biological effects. Microbiol Rev. 1992;56:265–79.
Dry I, Krake LR, Rigden JE, Rezaian MA. A novel subviral agent associated
with a geminivirus: the first report of a DNA satellite. Proc Natl Acad
Sci U S A. 1997;94:7088–93.
Behjatnia SAA, Dry IB, Rezaian MA. Identification of the replicationassociated protein binding domain within the intergenic region of tomato
leaf curl geminivirus. Nucleic Acids Res. 1998;26:925–31.
Saunders K, Bedford ID, Briddon RW, Markham PG, Wong SM, Stanley J.
A unique virus complex causes Ageratum yellow vein disease. Proc Natl
Acad Sci U S A. 2000;97:6890–5.
Tan HNP, Wong SM, Wu M, Bedford ID, Saunders K, Stanley J. Genome
organization of Ageratum yellow vein virus, a monopartite whitefly-transmitted
geminivirus isolated from a common weed. J Gen Virol. 1995;76:2915–22.
Stanley J, Saunders K, Pinner MS, Wong SM. Novel defective interfering
DNAs associated with ageratum yellow vein geminivirus infection of
Ageratum conyzoides. Virology. 1997;239:87–96.
Liu Y, Robinson DJ, Harrison BD. Defective forms of cotton leaf curl virus
DNA-A that have different combinations of sequence deletion, duplication,
inversion and rearrangement. J Gen Virol. 1998;79:1501–8.
Briddon RW, Mansoor S, Bedford ID, Pinner MS, Markham PG. Clones of
cotton leaf curl geminivirus induced symptoms atypical of cotton leaf curl
disease. Virus Genes. 2000;20:17–24.
Briddon RW, Mansoor S, Bedford ID, Pinner MS, Saunders K, Stanley J, et al.
Identification of DNA components required for induction of cotton leaf curl
disease. Virology. 2001;285:234–43.
Mansoor S, Khan SH, Bashir A, Saeed M, Zafar Y, Malik KA, et al. Identification
of a novel circular single-stranded DNA associated with cotton leaf curl
disease in Pakistan. Virology. 1999;259:190–9.
Briddon RW, Bull SE, Amin I, Mansoor S, Bedford ID, Rishi N, et al. Diversity
of DNA 1: a satellite-like molecule associated with monopartite
begomovirus-DNA β complexes. Virology. 2004;324:462–74.
Jose J, Usha R. Bhendi yellow vein mosaic disease in India is caused by
association of a satellite with a begomovirus. Virology. 2003;305:310–7.
Stenger DC, Revington GN, Stevenson MC, Bisaro DM. Replicational release
of geminivirus genomes from tandemly repeated copies: evidence for
rolling-circle replication of a plant viral DNA. Proc Natl Acad Sci U S A.
1991;88:8029–33.
Zhou X, Xie Y, Tao X, Zhang Z, Li Z, Fauquet CM. Characterization of DNAβ
associated with begomoviruses in China and evidence for co-evolution with
their cognate viral DNA-A. J Gen Virol. 2003;84:237–47.
Page 12 of 14
33. Briddon RW, Bull SE, Amin I, Idris AM, Mansoor S, Bedford ID, et al.
Diversity of DNA-β, a satellite molecule associated with some monopartite
begomoviruses. Virology. 2003;312:106–21.
34. Yang J-Y, Iwasaki M, Machinda C, Machinda Y, Zhou X, Chua N-H. βC1,
the pathogenicity factor of TYLCCNV, interacts with AS1 to alter leaf
development and suppress selective jasmonic acid responses. Genes Dev.
2008;22:2564–77.
35. Tao X, Zhou X. A modified viral satellite DNA that suppresses gene
expression in plants. Plant J. 2004;38:850–60.
36. Saunders K, Stanley J. A nanovirus-like component associated with yellow
vein disease of Ageratum conyzoides: evidence for inter-family recombination
between plant DNA viruses. Virology. 1999;264:142–52.
37. Mansoor S, Amin I, Hussain M, Zafar Y, Bull S, Briddon RW, et al. Association
of a disease complex involving a begomovirus, DNA1 and a distinct
DNA beta with leaf curl disease of okra in Pakistan. Plant Dis.
2001;85:922.
38. Mubin M, Briddon RW, Mansoor S. Complete nucleotide sequence of chilli
leaf curl virus and its associated satellites naturally infecting potato in
Pakistan. Arch Virol. 2009;154:365–8.
39. Gronenborn G. Nanoviruses: genome organization and protein function.
Vet Microbiol. 2004;98:103–10.
40. Huang C, Xie Y, Zhou X. Efficient virus-induced gene silencing in plants
using a modified geminivirus DNA1 component. Plant Biotechnol J.
2009;7:254–65.
41. Patil BL, Fauquet CM. Differential interaction between cassava mosaic
geminiviruses and geminivirus satellites. J Gen Virol. 2010;91:1871–82.
42. Paprotka T, Metzler V, Jeske H. The first DNA 1-like α satellites in association
with New World begomoviruses in natural infections. Virology.
2010;404:148–57.
43. Romay G, Chirinos D, Geraud-Pouey F, Desvies C. Association of an
atypical alphasatellite with a bipartite New World begomovirus.
Arch Virol. 2010;155:1843–7.
44. Nguessan KP, Fargette D, Fauquet C, Thouvenel JC. Aspects of the
epidemiology of okra leaf curl virus in Cote d’Ivoire. Trop Pest Man.
1992;38:122–6.
45. Fargette D, Jeger M, Fauquet CM, Fishpool LDC. Analysis of temporal
disease progress of African cassava mosaic virus. Phytopathology.
1993;84:91–8.
46. Swanson MM, Harrison BD. Properties, relationships and distribution of
cassava mosaic geminiviruses. Trop Sci. 1994;34:15–25.
47. Konate G, Barro N, Fargette D, Swanson MM, Harrison BD. Occurrence of
whitefly-transmitted geminiviruses in crops in Burkina-Faso, and their
serological detection and differentiation. Ann Appl Biol. 1995;126:121–9.
48. Czosnek H, Laterrot H. A worldwide survey of tomato yellow leaf curl
viruses. Arch Virol. 1997;142:1391–406.
49. Leke WN, Ramsell JNE, Njualem DK, Titanji VPK, Legg JP, Fondong VN, et al.
FTA technology facilitates detection and identification of begomoviruses
from okra plants in Cameroon. Afri Crop Sci Soc Conf Proc. 2007;8:655–60.
50. Leke WN, Kvarnheden A, Ngane EB, Titanji VPK, Brown JK. Molecular
characterization of a new begomovirus and divergent alphasatellite from
tomato in Cameroon. Arch Virol. 2011;156:925–8.
51. Leke WN, Brown JK, Ligthart ME, Sattar MN, Njualem DK, Kvarnheden A.
Ageratum conyzoides: A host to a unique begomovirus disease complex in
Cameroon. Virus Res. 2012;163:229–37.
52. Leke WN, Sattar MN, Ngane EB, Ngeve JM, Kvarnheden A, Brown JK.
Molecular characterization of begomoviruses and DNA satellites associated
with okra leaf curl disease in Cameroon. Virus Res. 2013;174:116–25.
53. Leke WN, Kvarnheden A. Mixed infection of two West African tomato-infecting
begomoviruses and Ageratum leaf curl Cameroon betasatellite infecting
tomato in Cameroon. Arch Virol. 2014;159:3145–8.
54. Zhou Y-C, Noussourou M, Kon T, Rojas MR, Jiang H, Chen L-F, et al. Evidence
of local evolution of tomato-infecting begomovirus species in West Africa:
characterization of Tomato leaf curl Mali virus and Tomato yellow crumple
virus from Mali. Arch Virol. 2008;153:693–706.
55. Chen L-F, Rojas M, Kon T, Gamby K, Xoconostle-Cazares B, Gilbertson RL. A
severe symptom phenotype in tomato in Mali is caused by a reassortant
between a novel recombinant begomovirus (Tomato yellow leaf curl Mali
virus) and a betasatellite. Mol Plant Pathol. 2009;10:415–30.
56. Kon T, Rojas MR, Abdourhamane IK, Gilbertson RL. Roles and interactions of
begomoviruses and satellite DNAs associated with okra leaf curl disease in
Mali. West Africa J Gen Virol. 2009;90:1001–13.
Leke et al. Agriculture & Food Security (2015) 4:1
57. Lett JM, Lefeuvre P, Couston L, Hoareau M, Thierry M, Reynaud B, et al.
Complete genomic sequences of Tomato yellow leaf curl Mali virus isolates
infecting tomato and pepper from the North Province of Cameroon.
Arch Virol. 2009;154:535–40.
58. Tiendrébéogo F, Lefeuvre P, Hoareau M, Villemot J, Konate G, Traoré AS,
et al. Molecular diversity of Cotton leaf curl Gezira virus isolates and their
satellite DNAs associated with okra leaf curl disease in Burkina Faso. Virol J.
2010;7:48.
59. Brown JK, Fauquet CM, Briddon RW, Zerbini M, Moriones E, Navas-Castillo J.
Family Geminiviridae. In: King AMQ, Adams MJ, Carstens EB, Lefkowitz EJ,
editors. Virus Taxonomy: Classification and Nomenclature of Viruses—Ninth
Report of the International Committee on Taxonomy of Viruses. USA:
Elsevier Academic Press; 2012. p. 351–73.
60. Bull SE, Tsai W-S, Briddon RW, Markham PG, Stanley J, Green SK. Diversity of
begomovirus DNA β satellites of non-malvaceous plants in east and south
east Asia. Arch Virol. 2004;149:1193–200.
61. Nawaz-ul-Rehman MS, Fauquet CM. Evolution of geminiviruses and their
satellites. FEBS Lett. 2009;583:1825–32.
62. Sivalingam PN, Malathi VG, Varma A. Molecular diversity of the DNA-β
satellites associated with tomato leaf curl disease in India. Arch Virol.
2010;155:757–64.
63. Briddon RW, Stanley J. Subviral agents associated with plant single-stranded
DNA viruses. Virology. 2006;344:198–210.
64. Shih SL, Kumar S, Tsai WS, Lee LM, Green SK. Complete nucleotide
sequences of okra isolates of Cotton leaf curl Gezira virus and their
associated DNA-β from Niger. Arch Virol. 2009;154:369–72.
65. Kon T, Gilbertson RL. Two genetically related begomoviruses causing
tomato leaf curl disease in Togo and Nigeria differ in virulence and host
range but do not require a betasatellite for induction of disease symptoms.
Arch Virol. 2012;157:107–20.
66. Briddon RW, Ghabrial S, Lin N-S, Palukaitis P, Scholthof K-BG, Vetten H- J.
Satellites and other virus-dependent nucleic acids. In: King AMQ, Adams MJ,
Carstens EB, Lefkowitz EJ, editors. Virus Taxonomy: Classification and
Nomenclature of Viruses—Ninth Report of the International Committee
on Taxonomy of Viruses. USA: Elsevier Acadmic Press; 2012. p. 1211–9.
67. Pasternak D, Senbeto D, Nikiema A, Kumar S, Fatondji D, Woltering L, et al.
Bioreclamation of degraded African lands with women empowerment.
Chronica Hortic. 2009;49:24–7.
68. AVRDC. 2014–2016 Medium-term Plan. Shanhua, Taiwan: AVRDC – The World
Vegetable Center; 2014. p. 14–776. 123 pp.
69. FAOSTAT. Food and Agricultural Organization of the United Nations. On-line
and Multilingual Database, 2014 http://faostat.fao.org.
70. Alvarez PA, Abud-Antún AJ. Reporte de Republica Dominicana. CEIBA
(Honduras). 1995;36:39–47.
71. Polston JE, Anderson PK. The emergence of whitefly-transmitted geminiviruses
in tomato in the Western Hemisphere. Plant Dis. 1997;81:1358–69.
72. Caballero R, Rueda A. Las moscas blancas en Honduras. In: Hilje L, Arboleda O,
editors. Las moscas blancas (Homoptera: Aleyrodidae) en America Central y El
Caribe. Turrialba, Costa Rica: CATIE; 1993. p. 50–3.
73. Fufa F, Hanson P, Dagnoko S, Dhaliwal M. AVRDC – The World Vegetable
Center tomato breeding in sub-Saharan Africa: Lessons from the past,
present work, and future prospects. Acta Hortic. 2011;911:87–98.
74. Camara M, Mbaye AA, Noba K, Samb PI, Diao S, Cilas C. Field screening of
tomato genotypes for resistance to Tomato yellow leaf curl virus (TYLCV)
disease in Senegal. Crop Protect. 2013;44:59–65.
75. Butterbach P, Verlaan MG, Dullemans A, Lohuis D, Visser RGF, Bai Y, et al.
Tomato yellow leaf curl virus resistance by Ty-1 involves increased cytosine
methylation of viral genomes and is compromised by cucumber mosaic
virus infection. Proc Natl Acad Sci U S A. 2014;111:12942–7.
76. Ozores-Hampton M, Stansly PA, McAvoy. Evaluation of round a Roma-type
tomato varieties and advanced breeding lines resistant to Tomato yellow
leaf curl virus in Florida. HortTechnology. 2013;23:689–98.
77. Ji Y, Scott JW, Hanson P, Graham E, Maxwell DP. Sources of resistance,
inheritance, and location of genetic loci conferring resistance to members
of the tomato-infecting begomoviruses. In: Czosnek H, editor. Tomato
Yellow Leaf Curl Virus Disease. Dordrecht: Springer; 2007. p. 343–62.
78. Dagnoko S, Hanson P, Fufa F, Kollo IA. Preliminary performance of tomato
breeding lines for yield, fruit quality and resistance to Tomato yellow leaf
curl disease. Acta Hortic. 2011;911:455–68.
79. Alegbejo MD. Whitefly transmitted plant viruses in Nigeria. J Sustain Agr.
2000;17:99–109.
Page 13 of 14
80. Vu TV, Choudhury NR, Mukherjee SK. Transgenic tomato plants expressing
artificial microRNAs for silencing the pre-coat and coat proteins of a
begomovirus, Tomato leaf curl New Delhi virus, show tolerance to infection.
Virus Res. 2013;172:35–45.
81. Medina-Hernández D, Rivera-Bustamante R, Tenllado F, Holguín-Penã RJ.
Effects and effectiveness of two RNAi constructs for resistance to
Pepper golden mosaic virus in Nicotiana benthamiana plants. Viruses.
2013;5:2931–45.
82. Reyes MI, Nash TE, Dallas MM, Ascencio-Ibáñez JT, Hanley-Bowdoin L.
Peptide aptamers that bind to geminivirus replication proteins confer a
resistance phenotype to tomato yellow leaf curl virus and tomato mottle
virus infection in tomato. J Virol. 2013;87:9691–706.
83. Kumar S, Dagnoko S, Haougui A, Ratnadass A, Pasternak D, Kouame C. Okra
(Abelmoschus spp.) in West and Central Africa: potential and progress on its
improvement. Afr. J Agric Res. 2010;5:3590–8.
84. Shetty AA, Singh JP, Singh D. Resistance to yellow vein mosaic virus in okra:
a review. Biol Agric Hortic. 2013;29:159–64.
85. Otoidobiga LC, Vincent C, Stewart KR. Susceptibility of field populations of
adult Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Eretmocerus
sp (Hymeoptera: Aphelinidae) to cotton insecticides in Burkina Faso (West
Africa). Pest Manag Sci. 2002;59:97–106.
86. Houndété TA, Kétoh GK, Hema OSA, Brévault T, Glitho IA, Martin T.
Insecticide resistance in field populations of Bemisia tabaci (Hemiptera:
Aleyrodidae) in West Africa. Pest Manag Sci. 2010;66:1181–5.
87. Gnankiné O, Bassolé IHN, Chandre F, Glitho I, Akogbeto M, Dabiré RK, et al.
Insecticide resistance in Bemisia tabaci Gennadius (Homoptera: Aleyrodidae)
and Anopheles gambiae Giles (Diptera: Culicidae) could compromise the
sustainability of malaria vector control strategies in West Africa. Acta Trop.
2013;128:7–17.
88. Ucko O, Cohen S, Ben-Joseph R. Prevention of virus epidemics by a crop-free
period in the Arava region of Israel. Phytoparasitica. 1998;26:313–21.
89. Gilbertson RL, Rojas MR, Kon T, Jaquez J. Introduction of Tomato yellow leaf
curl virus into the Dominican Republic: the development of a successful
integrated pest management system. In: Czosnek H, editor. Tomato Yellow
Leaf Curl Virus Disease. Dordrecht: Springer; 2007. p. 279–303.
90. Pfeiffer DG, Mullins DE, Gilbertson RL, Brewster CC, Westwood J, Miller SA,
et al. IPM packages developed for vegetable crops in West Africa.
Phytopathology. 2011;101:S228.
91. Antignus Y. The management of Tomato yellow leaf curl virus in
greenhouses and the open field, a strategy of manipulation. In: Czosnek H,
editor. Tomato Yellow Leaf Curl Virus Disease. Dordrecht: Springer; 2007.
p. 263–78.
92. Polston JE, Lapidot M. Management of Tomato yellow leaf curl virus: US
and Israel perspectives. In: Czosnek H, editor. Tomato Yellow Leaf Curl Virus
Disease. Dordrecht: Springer; 2007. p. 251–62.
93. Olasantan FO. Vegetable production in tropical Africa: status and strategies
for sustainable management. J Sustain Agr. 2007;30:41–70.
94. Kil E-J, Park J, Lee H, Kim J, Choi H-S, Lee K-Y, et al. Lamium amplexicaule
(Lamiaceae): a weed reservoir for tomato yellow leaf curl virus (TYLCV) in
Korea. Arch Virol. 2014;159:1305–11.
95. Brown JK, Bird J, Frohlich DR, Rosell RC, Bedford ID, Markham PG. The
relevance of variability within the Bemisia tabaci species complex to
epidemics caused by Subgroup III geminiviruses. In: Gerling D, Mayer RT,
editors. Bemisia '95: Taxonomy, Biology, Damage, Control and Management,
Brown JK, Bird J, Frohlich DR, Rosell RC, Bedford ID, Markham PG.
Wimborne, UK: Intercept Publications; 2005. p. 77–92.
96. Brown JK. Bemisia: phylogenetic biology of the Bemisia tabaci sibling
species group. In: Stansly PA, Naranjo SE, editors. Bemisia: Bionomics and
Management of a Global Pest. Dordrecht-Heidelberg-London-New York:
Springer; 2010. p. 31–67. 350pp.
97. Frohlich DI, Torres-Jerez ID, Bedford PG, Markham PG, Brown JK. A phylogeographic analysis of the Bemisia tabaci species complex based on mitochondrial DNA markers. Mol Ecol. 1999;8:1593–602.
98. Gill R, Brown JK. Systematics of Bemisia and Bemisia relatives: can molecular
techniques solve the Bemisia tabaci complex conundrum—a taxonomist’s
viewpoint. In: Stansly PA, Naranjo SE, editors. Bemisia: Bionomics and
Management of a Global Pest. Dordrecht-Heidelberg-London-New York:
Springer; 2010. p. 5–29. 350pp.
99. Brown JK, Coats S, Bedford ID, Markham PG, Bird J, Frohlich DR. Characterization
and distribution of esterase electromorphs in the whitefly, Bemisia tabaci (Genn.)
(Homoptera: Aleyrodidae). Biochem Genet. 1995;33:205–14.
Leke et al. Agriculture & Food Security (2015) 4:1
100. Brown JK. The Bemisia tabaci complex: genetic and phenotypic variability
drives begomovirus spread and virus diversification. APSnet Features. 2007.
10.1094/APSnetFeature-2007-0107.
101. D’Hondt MD, Russo M. Tomato yellow leaf curl in Senegal. Phytopathology.
1985;112:153–60.
102. Fauquet C, Thouvenel J-C. Plant viral diseases in the Ivory Coast. Paris: Editions
de 1’ORSTOM; 1987. p. 243.
103. Legg JP, Sseruwagi P, Boniface S, Okao-Okuja G, Shirima R, Bigirimana S,
et al. Spatio-temporal patterns of genetic change amongst cassava Bemisia
tabaci whiteflies driving virus pandemics in East and Central Africa. Virus
Res. 2014;186:61–75.
104. Burban C, Fishpool LDC, Fauquet C, Fargette D, Thouvenel J-C. Host-associated
biotypes within West African populations of the whitefly Bemisia tabaci (Genn.),
(Hom., Aleyrodidae). J Appl Entomol. 1992;113:416–23.
105. Abdullahi I, Winter S, Atiri GI, Thottappilly G. Molecular characterization of
whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae) populations infesting
cassava. Bull Entomol Res. 2003;93:97–106.
106. Gueguen G, Vavre F, Gnankine O, Peterschmitt M, Charif D, Chiel E, et al.
Endosymbiont metacommunities, mtDNA diversity and the evolution of
the Bemisia tabaci (Hemiptera: Aleyrodidae) species complex. Mol Ecol.
2010;19:4365–78.
107. Gnankiné O, Mouton L, Henri H, Terraz G, Houndeté T, Martin T, et al.
Distribution of Bemisia tabaci (Homoptera: Aleyrodidae) biotypes and their
associated symbiotic bacteria on host plants in West Africa. Insect Conserv
Divers. 2013;6:411–21.
108. Legg JP, Sseruwagi P, Boniface S, Okao-Okuja G, Shirima R, Bigirimana S,
et al. Spatio-temporal patterns of genetic change amongst cassava Bemisia
tabaci whiteflies driving virus pandemics in East and Central Africa. Virus
Res. 2013;186:61–75.
109. Doyle JJ, Doyle JL. Isolation of plant DNA from fresh tissue. Focus.
1990;12:13–5.
110. Doyle J. DNA protocols for plants. In: Hewitt GM et al., editors. Molecular
Techniques in Taxonomy, Vol 57 NATO ASI Series. Berlin Heidelberg:
Springer; 1991.
111. Ndunguru J, Taylor NJ, Yadav J, Aly H, Legg JP, Aveling T, et al. Application
of FTA technology for sampling, recovery and molecular characterization of viral
pathogens and virus-derived transgenes from plant tissues. Virol J. 2005;2:45.
112. Haible D, Kober S, Jeske H. Rolling circle amplification revolutionizes
diagnosis and genomics of geminiviruses. J Virol Methods. 2006;135:9–16.
113. Saiki RK, Gelfand DH, Stoffel S, Scharf SJ, Higuchi R, Horn GT, et al.
Primer-directed enzymatic amplification of DNA with a thermostable
DNA polymerase. Science. 1988;239:487–91.
114. Brown JK, Idris AM, Torres-Jerez I, Banks GK, Wyatt SD. The core region of
the coat protein gene is highly useful for establishing the provisional
identification and classification of begomoviruses. Arch Virol. 2001;146:1–18.
115. Wyatt SD, Brown JK. Detection of subgroup III geminivirus isolates in leaf
extracts by degenerate primers and polymerase chain reaction.
Phytopathology. 1996;86:1288–93.
116. Idris AM, Brown JK. Sinaloa tomato leaf curl geminivirus: biological and molecular
evidence for a new subgroup III virus. Phytopathology. 1998;88:648–57.
117. Rojas MR, Gilbertson RL, Russell DR, Maxwell DP. Use of degenerate primers
in the polymerase chain reaction to detect whitefly transmitted
geminiviruses. Plant Dis. 1993;77:340–7.
118. Rampersad SN, Umaharan P. Detection of begomoviruses in clarified plant
extracts: a comparison of standard, direct-binding, and immunocapture PCR
techniques. Phytopathology. 2003;93:1153–7.
119. Briddon RW, Bull SE, Mansoor S, Amin I, Markham PG. Universal primers for
the PCR-mediated amplification of DNA β: a molecule associated with some
monopartite begomoviruses. Mol Biotechnol. 2002;20:315–8.
120. Bull SE, Briddon RW, Markham PG. Universal primers for the PCR-mediated
amplification of DNA1: a satellite-like molecule associated with
begomovirus-DNA β complexes. Mol Biotechnol. 2003;23:83–6.
121. Blanco L, Bernad A, Lázaro JM, Martín G, Garmendia C, Salas M. Highly
efficient DNA synthesis by the phage phi 29 DNA polymerase. Symmetrical
mode of DNA replication. J Biol Chem. 1989;264:8935–40.
122. Dean FB, Nelson JR, Giesler TL, Lasken RS. Rapid amplification of plasmid
and phage DNA using Phi 29 DNA polymerase and multiply-primed rolling
circle amplification. Genome Res. 2001;11:1095–9.
123. Johne R, Muller H, Rector A, van Ranst M, Stevens H. Rolling-circle amplification
of viral DNA genomes using phi29 polymerase. Trends Microbiol.
2009;17:205–11.
View publication stats
Page 14 of 14
124. Inoue-Nagata AK, Albuquerque LC, Rocha WB, Nagata T. A simple method
for cloning the complete begomovirus genome using the bacteriophage
φ29 DNA polymerase. J Virol Methods. 2004;116:209–11.
125. Wyant PS, Strohmeier S, Schafer B, Krenz B, Assuncao IP, Lima GSD, et al.
Circular DNA genomics (circomics) exemplified for geminiviruses in bean
crops and weeds of northeastern Brazil. Virology. 2012;427:151–7.
126. Idris A, Al-Saleh M, Piatek MJ, Al-Shahwan I, Ali S, Brown JK. Viral
metagenomics: validation of genome enrichment coupled with next
generation sequencing reveals reproducibility between laboratory and
field samples, and reveals polymorphisms in begomovirus populations
from natural plant infections. Viruses. 2014;6:1219.
Submit your next manuscript to BioMed Central
and take full advantage of:
• Convenient online submission
• Thorough peer review
• No space constraints or color figure charges
• Immediate publication on acceptance
• Inclusion in PubMed, CAS, Scopus and Google Scholar
• Research which is freely available for redistribution
Submit your manuscript at
www.biomedcentral.com/submit