Present status of some virus diseases affecting legume crops in Tunisia, and partial characterization of Chickpea chlorotic stunt virus

Field surveys were conducted in Tunisia during the 2005‒2006, 2006‒2007 and 2009‒2010 growing seasons to identify viruses which produce yellowing, reddening and/or stunting symptoms of chickpea, faba bean and pea crops. Tissue blot immunoassay (TBIA) results showed that Chickpea chlorotic stunt virus (CpCSV) was the most common virus, followed by Faba bean necrotic yellows virus, Bean leafroll virus and Beet western yellows virus. The coat protein (CP) gene nucleotide sequence of seven CpCSV isolates collected from different regions of Tunisia was compared with sequences of five other isolates in the NCBI database. A homology tree of the CP nucleotide sequences was prepared and CpCSV isolates were grouped into two clusters. The first group contained two Tunisian CpCSV chickpea isolates collected from Bizerte and Kef; sequenced regions showed a high nucleotiode homology (95%) to that of the Ethiopian and Sudanese CpCSV isolates. The second group included five Tunisian isolates: two from chickpea, two from pea and one from faba bean, which showed a high homology (96%) when compared with the Moroccan, Egyptian and Syrian CpCSV isolates

Viruses affecting lentil (Lens culinaris Medik.) in Greece; incidence and genetic variability of Bean leafroll virus and Pea enation mosaic virus

In Greece, lentil (Lens culinaris Medik.) crops are mainly established with non-certified seeds of local landraces, implying high risks for seed transmitted diseases. During April and May of the 2007–2012 growing seasons, surveys were conducted in eight regions of Greece (Attiki, Evros, Fthiotida, Korinthos, Kozani, Larissa, Lefkada and Viotia) to monitor virus incidence in lentil fields. A total of 1216 lentil samples, from plants exhibiting symptoms suggestive of virus infection, were analyzed from 2007 to 2009, using tissue-blot immunoassays (TBIA). Pea seed-borne mosaic virus (PSbMV) overall incidence was 4.9%, followed by Alfalfa mosaic virus (AMV) (2.4%) and Bean yellow mosaic virus (BYMV) (1.0%). When 274 of the samples were tested for the presence of luteoviruses, 38.8% were infected with Bean leafroll virus (BLRV). Since BLRV was not identified in the majority of the samples collected from 2007 to 2009, representative symptomatic plants (360 samples) were collected in further surveys performed from 2010 to 2012 and tested by ELISA. Two viruses prevailed in those samples: BLRV (36.1%) was associated with stunting, yellowing, and reddening symptoms and Pea enation mosaic virus-1 (PEMV-1) (35.0%) was associated with mosaic and mottling symptoms. PSbMV (2.2%), AMV (2.2%), BYMV (3.9%) and CMV (2.8%) were also detected. When the molecular variability was analyzed for representative isolates, collected from the main Greek lentil production areas, five BLRV isolates showed 95% identity for the coat protein (CP) gene and 99% for the 3’ end region. Three Greek PEMV isolates co-clustered with an isolate from Germany when their CP sequence was compared with isolates with no mutation in the aphid transmission gene. Overall, limited genetic variability was detected among Greek isolates of BLRV and PEMV

Characterization of a Syrian Chickpea chlorotic stunt virus strain and production of polyclonal antibodies for its detection

Reverse transcription-polymerase chain reaction analysis with two primer sets of luteoviruses was used to characterize an isolate of Chickpea chlorotic stunt virus (CpCSv, genus Polerovirus, family Luteoviridae) (SC402-08) collected from Lattakia, Syria, during the 2007‒2008 chickpea growing season. Sequence analysis revealed that the coat protein gene of the isolate shared nucleotide sequence identities ranging from 97 to 98% with the CpCSv isolates from Egypt, morocco and Syria. The capsid protein was separated as a protein of approximately 20 kDa in sodium dodecyl sulphate polyacrylamide gel electrophoresis, and was visually detected by its reaction with CpCSV monoclonal antibody in Western blot. SC402-08 isolate of CpCSV was purified from faba bean-infected plants, and yielded 112–182 μg of purified virions kg-1 of infected tissue. The purified preparation was injected into a white rabbit, and an antiserum was obtained and used to detect CpCSv in infected tissues by tissue-blot immunoassay. The antiserum obtained was able to detect CpCSv by the immunoassay up to a dilution of 1:1,024,000

Viral diseases affecting chickpea crops in Eritrea

A survey to identify virus diseases affecting chickpea crops in the major production areas of Eritrea was conducted during November 2005. The survey covered 31 randomly selected chickpea fi elds. Virus disease incidence was determined on the basis of laboratory testing of 100–200 randomly collected samples from each fi eld against antisera of 9 legume viruses. Serological tests indicated that the Luteoviruses were the most common, with an overall incidence of 5.6%, followed by Faba bean necrotic yellows virus (FBNYV, genus Nanovirus, family Nanoviridae) (4.1%) and Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus, family Geminiviridae) (0.9%). The reverse transcription polymerase chain reaction (RT-PCR) test showed that the most common luteoviruses in Eritrea are Chickpea chlorotic stunt virus (CpCSV) followed by Beet western yellows virus (BWYV, genus Polerovirus, family Luteoviridae). Based on the fi eld symptoms observed, 29 fi elds had, at the time of the survey, a virus disease incidence of 1% or less and only two fi elds had an incidence of about 5%, whereas on the basis of laboratory testing, 19 fi elds had more than 6% virus incidence (three of these had an incidence of 29.5, 34.5 and 40.5%). This is the fi rst survey of chickpea viruses in Eritrea and the fi rst report of BWYV, CpCDV, CpCSV and FBNYV naturally infecting chickpea in Eritrea

Evidence that dicot-infecting mastreviruses are particularly prone to inter-species recombination and have likely been circulating in Australia for longer than in Africa and the Middle East

Viruses of the genus Mastrevirus (family Geminiviridae) are transmitted by leafhoppers and infect either mono- or dicotyledonous plants. Here we have determined the full length sequences of 49 dicot-infecting mastrevirus isolates sampled in Australia, Eritrea, India, Iran, Pakistan, Syria, Turkey and Yemen. Comprehensive analysis of all available dicot-infecting mastrevirus sequences showed the diversity of these viruses in Australia to be greater than in the rest of their known range, consistent with earlier studies, and that, in contrast with the situation in monocot-infecting mastreviruses, detected inter-species recombination events outnumbered intra-species recombination events. Consistent with Australia having the greatest diversity of known dicot-infecting mastreviruses phylogeographic analyses indicating the most plausible scheme for the spread of these viruses to their present locations, suggest that most recent common ancestor of these viruses is likely nearer Australia than it is to the other regions investigated.Department of HE and Training approved lis

The westward journey of alfalfa leaf curl virus

Alfalfa leaf curl virus (ALCV), which causes severe disease symptoms in alfalfa (Medicago sativa L.) and is transmitted by the widespread aphid species, Aphis craccivora Koch, has been found throughout the Mediterranean basin as well as in Iran and Argentina. Here we reconstruct the evolutionary history of ALCV and attempt to determine whether the recent discovery and widespread detection of ALCV is attributable either to past diagnostic biases or to the emergence and global spread of the virus over the past few years. One hundred and twenty ALCV complete genome sequences recovered from ten countries were analyzed and four ALCV genotypes (ALCV-A, ALCV-B, ALCV-C, and ALCV-D) were clearly distinguished. We further confirm that ALCV isolates are highly recombinogenic and that recombination has been a major determinant in the origins of the various genotypes. Collectively, the sequence data support the hypothesis that, of all the analyzed locations, ALCV likely emerged and diversified in the Middle East before spreading to the western Mediterranean basin and Argentina

New World Cactaceae Plants Harbor Diverse Geminiviruses

The family Cactaceae comprises a diverse group of typically succulent plants that are native to the American continent but have been introduced to nearly all other continents, predominantly for ornamental purposes. Despite their economic, cultural, and ecological importance, very little research has been conducted on the viral community that infects them. We previously identified a highly divergent geminivirus that is the first known to infect cacti. Recent research efforts in non-cultivated and asymptomatic plants have shown that the diversity of this viral family has been under-sampled. As a consequence, little is known about the effects and interactions of geminiviruses in many plants, such as cacti. With the objective to expand knowledge on the diversity of geminiviruses infecting cacti, we used previously acquired high-throughput sequencing results to search for viral sequences using BLASTx against a viral RefSeq protein database. We identified two additional sequences with similarity to geminiviruses, for which we designed abutting primers and recovered full-length genomes. From 42 cacti and five scale insects, we derived 42 complete genome sequences of a novel geminivirus species that we have tentatively named Opuntia virus 2 (OpV2) and 32 genomes of an Opuntia-infecting becurtovirus (which is a new strain of the spinach curly top Arizona virus species). Interspecies recombination analysis of the OpV2 group revealed several recombinant regions, in some cases spanning half of the genome. Phylogenetic analysis demonstrated that OpV2 is a novel geminivirus more closely related to viruses of the genus Curtovirus, which was further supported by the detection of three recombination events between curtoviruses and OpV2. Both OpV2 and Opuntia becurtoviruses were identified in mixed infections, which also included the previously characterized Opuntia virus 1. Viral quantification of the co-infected cactus plants compared with single infections did not show any clear trend in viral dynamics that might be associated with the mixed infections. Using experimental Rhizobium-mediated inoculations, we found that the initial accumulation of OpV2 is facilitated by co-infection with OpV1. This study shows that the diversity of geminiviruses that infect cacti is under-sampled and that cacti harbor diverse geminiviruses. The detection of the Opuntia becurtoviruses suggests spill-over events between viruses of cultivated species and native vegetation. The threat this poses to cacti needs to be further investigated