Begomovirus 'melting pot' in the south-west Indian Ocean islands: molecular diversity and evolution through recombination

During the last few decades, many virus species have emerged, often forming dynamic complexes within which viruses share common hosts and rampantly exchange genetic material through recombination. Begomovirus species complexes are common and represent serious agricultural threats. Characterization of species complex diversity has substantially contributed to our understanding of both begomovirus evolution, and the ecological and epidemiological processes involved in the emergence of new viral pathogens. To date, the only extensively studied emergent African begomovirus species complex is that responsible for cassava mosaic disease. Here we present a study of another emerging begomovirus species complex which is associated with serious disease outbreaks in bean, tobacco and tomato on the south-west Indian Ocean (SWIO) islands off the coast of Africa. On the basis of 14 new complete DNA-A sequences, we describe seven new island monopartite begomovirus species, suggesting the presence of an extraordinary diversity of begomovirus in the SWIO islands. Phylogenetic analyses of these sequences reveal a close relationship between monopartite and bipartite African begomoviruses, supporting the hypothesis that either bipartite African begomoviruses have captured B components from other bipartite viruses, or there have been multiple B-component losses amongst SWIO virus progenitors. Moreover, we present evidence that detectable recombination events amongst African, Mediterranean and SWIO begomoviruses, while substantially contributing to their diversity, have not occurred randomly throughout their genomes. We provide the first statistical support for three recombination hot-spots (V1/C3 interface, C1 centre and the entire IR) and two recombination cold-spots (the V2 and the third quarter of V1) in the genomes of begomoviruses.

Quasispecies nature of three maize streak virus isolates obtained through different modes of selection from a population used to assess response to infection of maize cultivars

Three maize streak virus (MSV) isolates were derived from an MSV population used to assess the response to infection of maize cultivars. Isolate SP1 was obtained from this population through short acquisition and inoculation periods (1 and 5 min, respectively), using a single Cicadulina mbila vector. Isolate SP2 was derived from SP1 after transmission to a wild perennial host (Coix lacryma-jobi), on which it was maintained for about 4 years without insect transmission. Isolate N2A, the most pathogenic isolate, was obtained from the initial population after serial passages on almost completely resistant inbred maize lines. The complexity of each isolate was analysed by RFLP analysis and sequencing based on 120 SP1 clones, 36 SP2 clones and 40 N2A clones. All three isolates were composed of different but related clones, consistent with a quasispecies structure. The mutations were distributed throughout the genome. Mutation frequencies, based on all available sequences, were 3.8 x 10(-4) for SP1, 10.5 x 10(-4) for SP2 and 6.9 x 10(-4) for N2A. As expected from the bottleneck selection step, the intra-isolate variability of SP1 was relatively low. Comparison between SP1 and SP2 showed that SP1 heterogeneity increased during maintenance on the wild host. Furthermore, the consensus sequences of SP1 and SP2 differed by two non-synonymous substitutions in the complementary sense gene repA. N2A had a relatively low degree of heterogeneity, but was composed of several sub-populations. The results reflect the influence of the mode of selection of MSV isolates on their quasispecies organization, i.e. distribution of variants, and master sequence.

Honeybee biomarkers as promising tools to monitor environmental quality

The aim of this study was to distinguish the impacts of two different anthropogenic conditions using the honeybee Apis mellifera as a bioindicator associated with a battery of biomarkers previously validated in the laboratory. Both the urban (RAV, Ravine des Cabris) and semi-natural (CIL, Cilaos) sites in La Reunion Island were compared in order to assess the impacts of two types of local pollution using the discriminating potential of biomarkers. Hives were placed at the CIL and RAV sites and honeybees were collected from each hive every three months over one year. Honeybee responses were evaluated with respect to several biochemical biomarkers: glutathione-S-transferase (GST), acetylcholinesterase (AChE), alkaline phosphatase (ALP) and metallothioneins (MT). The results showed a significant difference between the localities in terms of GST, AChE and ALP activities, as regarding midgut MT tissue levels. Compared to the CIL site, ALP and MT tissue levels were higher at the RAV site, although AChE activity was lower. GST displayed more contrasted effects. These results strongly suggest that the honeybees based in the more anthropized area were subjected to sublethal stress involving both oxidative stress and detoxification processes with the occurrence of neurotoxic pollutants, amongst which metals were good candidates. A classification tree enabled defining a decision procedure to distinguish the sampling locations and enabled excellent classification accuracy (89%) for the data set. This field study constitutes a strong support in favour of the in situ assessment of environmental quality using honeybee biomarkers and validates the possibility of performing further ecotoxicological studies using honeybee biomarkers.

A new silverleaf-inducing biotype Ms of Bemisia tabaci (Hemiptera: Aleyrodidae) indigenous to the islands of the south-west Indian Ocean

Following the first detection of tomato yellow leaf curl virus (TYLCV) from Reunion (700 km east of Madagascar) in 1997 and the upsurge of Bemisia tabaci (Gennadius) on vegetable crops, two genetic types of B. tabaci were distinguished using RAPD-PCR and cytochrome oxidase I (COI) gene sequence comparisons. One type was assigned to biotype B and the other was genetically dissimilar to the populations described elsewhere and was named Ms, after the Mascarenes Archipelago. This new genetic type forms a distinct group that is sister to two other groups, one to which the B biotype is a member and one to which the Q biotype belongs. The Ms biotype is thought to be indigenous to the region as it was also detected in Mauritius, the Seychelles and Madagascar. Both B and Ms populations of B. tabaci induced silverleaf symptoms on Cucurbita sp., and were able to acquire and transmit TYLCV. Taken together these results indicate that the Ms genetic type should be considered a new biotype of B. tabaci.

Microsatellites reveal extensive geographical, ecological and genetic contacts between invasive and indigenous whitefly biotypes in an insular environment

Human-mediated bioinvasions provide the opportunity to study the early stages of contact between formerly allopatric, divergent populations of a species. However, when invasive and resident populations are morphologically similar, it may be very difficult to assess their distribution in the field, as well as the extent of ecological overlap and genetic exchanges between invasive and resident populations. We here illustrate the use of data obtained from a set of eight microsatellite markers together with Bayesian clustering methods to document invasions in a group of major tropical pests, Bemisia tabaci, which comprises several morphologically indistinguishable biotypes with different agronomic impacts. We focus on the island of La Réunion, where an invasive biotype (B) has recently been introduced and now interacts with the resident biotype (Ms). The temporal and spatial distribution, host-plant range and genetic structure of both biotypes are investigated. We showed (i) that, without prior information, clustering methods separate two groups of individuals that can safely be identified as the B and Ms biotypes; (ii) that the B biotype has invaded all regions of the island, and showed no signs of genetic founder effect relative to the Ms biotype; (iii) that the B and Ms biotypes coexist in sympatry throughout most of their geographical ranges, although they tend to segregate into different host plants; and finally (iv) that asymmetrical and locus-specific introgression occurs between the two biotypes when they are in syntopy.

Andris M, Aradottir GI, Arnau G, Audzijonyte A, Bess EC, Bonadonna F, Bourdel G, Bried J, Bugbee GJ, Burger PA, Chair H, Charruau PC, Ciampi AY, Costet L, Debarro PJ, Delatte H, Dubois MP, Eldridge MDB, England PR, Enkhbileg D, Fartek B, Gardner MG, Gray KA, Gunasekera RM, Hanley SJ, Havil N, Hereward JP, Hirase S, Hong Y, Jarne P, Jianfei Q, Johnson RN, Kanno M, Kijima A, Kim HC, Kim KS, Kim WJ, Larue E, Lee JW, Lee JH, Li C, Liao M, Lo N, Lowe AJ, Malausa T, Malé PJG, Marko MD, Martin JF, Messing R, Miller KJ, Min BW, Myeong JI, Nibouche S, Noack AE, Noh JK, Orivel J, Park CJ, Petro D, Prapayotin-Riveros K, Quilichini A, Reynaud B, Riginos C, Risterucci AM, Rose HA, Sampaio I, Silbermayr K, Silva MB, Tero N, Thum RA, Vinson CC, Vorsino A, Vossbrinck CR, Walzer C, White JC, Wieczorek A, Wright M. Permanent Genetic Resources added to Molecular Ecology Resources Database 1 June 2010 - 31 July 2010

This article documents the addition of 205 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Bagassa guianensis, Bulweria bulwerii, Camelus bactrianus, Chaenogobius annularis, Creontiades dilutus, Diachasmimorpha tryoni, Dioscorea alata, Euhrychiopsis lecontei, Gmelina arborea, Haliotis discus hannai, Hirtella physophora, Melanaphis sacchari, Munida isos, Thaumastocoris peregrinus and Tuberolachnus salignus. These loci were cross-tested on the following species: Halobaena caerulea, Procellaria aequinoctialis, Oceanodroma monteiroi, Camelus ferus, Creontiades pacificus, Dioscorea rotundata, Dioscorea praehensilis, Dioscorea abyssinica, Dioscorea nummularia, Dioscorea transversa, Dioscorea esculenta, Dioscorea pentaphylla, Dioscorea trifida, Hirtella bicornis, Hirtella glandulosa, Licania alba, Licania canescens, Licania membranaceae, Couepia guianensis and 7 undescribed Thaumastocoris species.

A multiplex PCR method discriminating between the TYLCV and TYLCV-Mld clades of tomato yellow leaf curl virus

Tomato yellow leaf curl virus (TYLCV) is one of the causal agents of tomato yellow leaf curl disease (TYLCD) and can cause up to 100% yield losses in tomato fields. As TYLCV continues to spread, many isolates have been described in different parts of the world. Recently two closely related but distinct TYLCV clades, called TYLCV and TYLCV-Mld, have been identified. Isolates from those two clades differ mainly in the nucleotide sequences of their replication associated protein genes but do not display significantly different symptomatology. In order to improve monitoring of the rapidly expanding worldwide TYLCD epidemic, a multiplex polymerase chain reaction assay (mPCR) was developed. A set of three primers were designed to detect and characterize the TYLCV and TYLCV-Mld clade isolates. The specificity and sensitivity of the mPCR were validated on TYLCV infected tomato plants and Bemisia tabaci whiteflies. Being cheap, fast and highly sensitive this new diagnostic tool should greatly simplify efforts to trace the global spread of TYLCV.

Infectivity and complete nucleotide sequence of the genome of a genetically distinct strain of maize streak virus from Reunion Island

A complete infectious genome of an isolate of maize streak subgroup 1 geminivirus from Reunion Island (MSV-R) was cloned and sequenced. Using an Agrobacterium tumefaciens Ti plasmid delivery system, the cloned 2.7 kb circular DNA was shown to be infectious in maize. The agroinfected virus could be transmitted by Cicadulina mbila, the most common vector species of MSV in Reunion. Analysis of open reading frames (ORFs) revealed seven potential coding regions including the 4 ORFs conserved in all geminiviruses infecting monocotyledonous plants, the 2 on the viral "+" strand (MP, CP), and the 2 on the complementary "-" strand (RepA, RepB). The nucleotide sequence of MSV-R was compared to previously determined sequence of three African clones from Nigeria (MSV-N), Kenya (MSV-K), and South Africa (MSV-S). More similarity was found between the African clones (97.0-97.3%) than between these and MSV-R (94.4-95.3%). Nucleotide substitutions were frequent in the large intergenic region, particularly in and around the most likely TATA box for the complementary sense genes, and in the 5' end of ORF V1. The comparison of the predicted peptide sequences of the proteins encoded by ORFs MP, RepA and RepB confirmed the higher similarity between the African clones (97.8-99.3%) than between these and MSV-R (95.1-97.1%). However the amino acid sequences of the protein encoded by ORF CP (capsid protein) were very conserved among all the 4 clones, suggesting a high selection pressure on this ORF.

First Report of Tomato Yellow Leaf Curl Virus in Réunion Island

In September 1997, stunting, reduced leaf size, leaf curling, and yellow margins were observed on tomato plants on a farm on the south coast of Réunion, a French island belonging to the Mascarenes archipelago. To our knowledge, these symptoms appeared to be characteristic of a tomato yellow leaf curl virus (TYLCV) infection. Diseased plants gave positive reactions with a triple antibody sandwich-enzyme-linked immunosorbent assay (TAS-ELISA), using ADGEN antibodies specific for begomoviruses (1). The serological results were confirmed by polymerase chain reaction (PCR) with a pair of degenerate primers-MP16, 5'-CCTCTAGATAATATTAC(C/T)(G/T)(G/A)(A/T)(T/G)G(G/A)CC-3' and MP82, 5'-CGGAATTC(T/C)TGNAC(C/T)TT(G/A)CANGGNCC(T/C)T C(G/A)CA-3'-designed by Malla Padidam (ILTAB, San Diego, CA) to amplify a region of the A component of begomoviruses, between the intergenic conserved nonanucleotide sequence (TAATATTAC) and the first 5' quarter of the capsid protein gene. A 500-bp PCR product was obtained from a symptomatic plant but not from a healthy looking one. After cloning the PCR product in a pGEM-T Easy vector (Promega, Madison, WI) and sequencing it with plasmid-specific primers (SP6, T7), the sequence was compared with the sequences of the NCBI data base, with the use of BLAST. Nineteen sequences among those producing the highest scoring segment pairs were compared with each other and with the 500-bp PCR product from Réunion by the Clustal method of MegAlign (DNASTAR, London). The Réunion sequence (AJ010790) was at least 94% similar to sequences of TYLCV isolates from the Dominican Republic (AF024715), Cuba (AJ223505), and Israel (X15656, X76319 for the mild clone). Based on these results, it appeared that the analyzed tomato plant was infected by a geminivirus isolate belonging to the Israeli species of TYLCV. A preliminary survey was carried out from December 1997 to April 1998 in both outdoor and protected tomato crops. Infected plants were detected by TAS-ELISA in 52 of the 123 locations visited. Severe economic losses were observed: 14 locations with 60 to 100% yield reduction and 11 locations with 40 to 60% yield reduction. All the infected samples were collected in the leeward coast, which is the driest region of the island. Although Bemisia tabaci (Gennadius) has been recorded since 1938 in Réunion (2), it has been observed on tomato crops only since 1997 and population levels were low compared with those of Trialeurodes vaporariorum Westwood. During the first six months of 1998, B. tabaci was found on Euphorbia heterophylla L., Lantana camara L., Solanum melongena L., S. nigrum L., and Phaseolus vulgaris L. These host plants often occur near infected tomato crops. References: (1) S. Macintosh et al. Ann. Appl. Biol. 121:297, 1992. (2) L. Russell and J. Etienne. Proc. Entomol. Soc. Wash. 87:202, 1985.

Genetic diversity, geographical range and origin of Bemisia tabaci (Hemiptera: Aleyrodidae) Indian Ocean Ms

The whitefly Bemisia tabaci is a pest vector of begomoviruses on crops worldwide. Bemisia tabaci is composed of a complex of cryptic species which barely interbreed. An exception is the Ms from the South West Indian Ocean (SWIO), which crosses in low proportions with the exotic B. The Ms, together with B and Q is part of the same phylogenetic clad. To infer the genetic structure, the geographical range and putative origin of this putative species, microsatellite data and mitochondrial DNA (cytochrome oxydase I) sequences were analysed on an extensive sample set, including all the islands of the region and samples from mainland Africa. Only B and Ms populations were detected across these islands. The exotic B was found only on the islands of Réunion and Mauritius, whereas the Ms is found on all the SWIO islands. Very high isolation by distance was found for the Ms populations between islands of the SWIO, suggesting a long period of presence in this region. Ms populations from mainland Africa had a higher COI diversity than the Ms of the SWIO islands. This diversity is correlated with size and geological ages of the SWIO islands. The population genetic data obtained are in accordance with an origin of Ms in Africa, followed by its expansion and evolution across the SWIO islands prior to human arrival, confirming the status of Ms as indigenous in the SWIO islands.

Genetic mapping of maize streak virus resistance from the Mascarene source. I. Resistance in line D211 and stability against different virus clones

Maize streak virus (MSV) disease may cause significant grain yield reductions in maize in Africa. Réunion island maize germplasm is a proven source of strong resistance. Its genetic control was investigated using 123 RFLP markers in an F(2) population of D211 (resistant) × B73 (susceptible). This population of 165 F(2:3) families was carefully evaluated in Harare (Zimbabwe) and in Réunion. Artificial infestation was done with viruliferous leafhoppers. Each plant was rated weekly six times after infestation on a 1-9 scale previously adjusted by image analysis. QTL analyses were conducted for each scoring date, and for the areas under the disease, incidence and severity progress curves. The composite interval mapping method used allowed the estimation of the additive and dominance effects and QTL × environment interactions. Heritabilities ranged from 73% to 98%, increasing with time after infestation. Resistance to streak virus in D211 was provided by one region on chromosome 1, with a major effect, and four other regions on chromosomes 2, 3 (two regions) and 10, with moderate or minor effects. Overall, they explained 48-62% of the phenotypic variation for the different variables. On chromosome 3, one of the two regions seemed to be more involved in early resistance, whereas the second was detected at the latest scoring date. Other QTLs were found to be stable over time and across environments. Mild QTL × environment interactions were detected. Global gene action appeared to be partially dominant, in favor of resistance, except at the earliest scoring dates, where it was additive. From this population, 32 families were chosen, representing the whole range of susceptibility to MSV. They were tested in Réunion against three MSV clones, along with a co-inoculation of two of them. Virulence differences between clones were significant. There were genotype × clone interactions, and these were more marked for disease incidence than for severity. Although these interactions were not significant for the mean disease scores, it is suggested that breeders should select for completely resistant genotypes.

Tomato yellow leaf curl virus Can Be Acquired and Transmitted by Bemisia tabaci (Gennadius) from Tomato Fruit

The whitefly Bemisia tabaci is an insect pest causing worldwide economic losses, especially as a vector of geminiviruses such as Tomato yellow leaf curl virus (TYLCV). Currently, imported and exported tomato fruit are not monitored for TYLCV infection because they are not considered to represent a potential risk as a virus source for whiteflies. A survey of tomato fruit imported into Réunion Island indicated that more than 50% of the fruit contained TYLCV as determined by DNA blot analysis. Moreover, we showed that TYLCV was present at a high titer in tomato fruit, and demonstrated that it can be acquired by whiteflies and subsequently transmitted to healthy tomato plants. Potential risk of the spread of TYLCV by tomato fruit in natural conditions needs to be further assessed.

First Report of Tomato chlorosis virus in Tomato on Mauritius Island

In February of 2007, a virus disease survey on tomato plants (Solanum lycopersicum) in greenhouses and open fields was conducted on the island of Mauritius at the request of the Agricultural Research and Extension Unit (AREU), sponsored by the European Union, and funded by the Programme Régional de Protection des Végétaux (PRPV). Yellowing symptoms on the lower and middle leaves of tomato plants and whiteflies (Bemisia tabaci) were observed in greenhouses in Pailles, located in the north region of the island. The interveinal chlorosis pattern of the discolored leaves was similar to symptoms described for Tomato chlorosis virus (ToCV; genus Crinivirus) detected on tomato in 2004 on Reunion Island (1), suggesting the possible involvement of the same virus. Six symptomatic tomato leaf samples were collected from separate plants in the Pailles greenhouses. Total RNA was extracted from these samples with the Qiagen (Courtaboeuf, France) RNeasy Plant Mini Kit. Reverse transcription-PCR was used for molecular diagnosis, independently using two sets of specific ToCV primers. The first set of primers, ToCV-172 and ToCV-610, was designed to amplify the highly conserved region of the heat shock protein 70 (HSP70) gene (2). The second set of primers was designed to amplify the coat protein (CP) gene (forward-CP-ToCV-4384: 5'-ATCCTCTGGTTAGACCGTTAG-3' and reverse as in Segev et al. [3]). PCR products of the expected size (439 and 725 bp, respectively) were observed for the six samples from the greenhouse from Pailles. For each set of primers, two PCR products obtained from two different samples were cloned using the pGEM-T Easy Vector system (Promega, Madison, WI) and sequenced (Macrogen, Seoul, Korea). The two HSP70 sequences (GenBank-EMBL-DDBJ Accession Nos. AM884013 and AM884014) and the two CP sequences (FM206381 and FM206382) had 100% nucleotide identities (DNAMAN; Lynnon BioSoft, Quebec City, Canada). The highest nucleotide identities of the 439-bp fragment of HSP70 gene (NCBI, BLASTn) were 97% with ToCV isolates from France (DQ355214, DQ355215, and DQ355216), Florida (AY903448), Italy (AM231038 and AY048854), Mayotte Island (AM748818), Portugal (AF234029), and Reunion Island (AM748816). Similarly, the highest nucleotide identities (98%) were obtained with ToCV isolates from France (EU625350) and Spain (DQ136146), with the 725-bp fragments of CP gene. Interestingly, ToCV isolates from Mauritius and Reunion are as divergent as isolates from the rest of the world, which suggests the possibility of different introductions. In conclusion, observed symptoms and laboratory results based on two different regions of the genome confirm the presence of ToCV in symptomatic tomatoes on the island of Mauritius, for the first time to our knowledge. The visual survey carried out in June of 2008 confirmed the presence of typical interveinal chlorosis symptoms in other greenhouses, requiring further studies to assess the incidence of ToCV on tomato crops. References: (1) H. Delatte et al. Plant Pathol. 55:289, 2006. (2) D. Louro et al. Eur. J. Plant Pathol. 106:589, 2000. (3) L. Segev et al. Plant Dis. 88:1160, 2004.

Differential disease phenotype of begomoviruses associated with tobacco leaf curl disease in Comoros

In the 2000s, tobacco plantations on the Comoros Islands were afflicted with a previously unobserved tobacco leaf curl disease characterised by symptoms of severe leaf curling and deformation. Previous molecular characterization of potential viral pathogens revealed a complex of African monopartite tobacco leaf curl begomovirus (TbLCVs). Our molecular investigation allowed the characterization of a new monopartite virus involved in the disease: tomato leaf curl Namakely virus (ToLCNamV). Agroinoculation experiments indicated that TbLCVs and tomato leaf curl viruses (ToLCVs) can infect both tomato and tobacco but that infectivity and symptom expression fluctuate depending on the virus and the plant cultivar combination.

Haemorrhagic shock, therapeutic management

The management of a patient in post-traumatic haemorrhagic shock will meet different logics that will apply from the prehospital setting. This implies that the patient has beneficiated from a "Play and Run" prehospital strategy and was sent to a centre adapted to his clinical condition capable of treating all haemorrhagic lesions. The therapeutic goals will be to control the bleeding by early use of tourniquet, pelvic girdle, haemostatic dressing, and after admission to the hospital, the implementation of surgical and/or radiological techniques, but also to address all the factors that will exacerbate bleeding. These factors include hypothermia, acidosis and coagulopathy. The treatment of these contributing factors will be associated to concepts of low-volume resuscitation and permissive hypotension into a strategy called "Damage Control Resuscitation". Thus, the objective in situation of haemorrhagic shock will be to not exceed a systolic blood pressure of 90 mmHg (in the absence of severe head trauma) until haemostasis is achieved.

Evaluation of Maize Inbreds for Maize stripe virus and Maize mosaic virus Resistance: Disease Progress in Relation to Time and the Cumulative Number of Planthoppers

ABSTRACT Five tropical maize lines were tested and compared with the susceptible control line B73 for resistance to Maize stripe virus (MStV) and Maize mosaic virus (MMV), both propagatively transmitted by the planthopper Peregrinus maidis (Homoptera: Delphacidae). Resistance to each virus was evaluated separately by artificial inoculations with planthoppers viruliferous for either one virus or the other. Disease incidence and symptom severity progression were quantified in relation to time and the cumulative number of planthoppers. Line Hi40 was found to be susceptible to MStV and highly resistant to MMV. Generally, no MMV symptoms developed on Hi40, even under intense inoculation pressure by a large number of viruliferous planthoppers. Line Rev81 showed a partial but strong resistance to MStV, which mainly reduced disease incidence. Nevertheless, this resistance to MStV was the highest ever reported and held up, even when challenged by large numbers of planthoppers. The percentage of infected plants in line Rev81 never exceeded 30 to 40% in our experiments. Moderate levels of resistance to MStV, and to a lesser extent MMV, were found in lines 37-2, A211, and Mp705. However, resistance in these lines was completely overcome using a large number of insects transmitting either of the two viruses. These results suggest that different types of resistance to MMV and MStV are available in maize lines from Caribbean and Mascarene germ plasm. The expression of virus-specific resistance identified in Hi40 and Rev81 lines was not affected by intense inoculation pressure. In contrast, the moderate resistance in 37-2, A211, and Mp705 was partially effective against both viruses but not at high inoculation pressure. These different types of resistance, when present in the same genotype, could provide protection against both viruses.

Assessing hygienic behavior of Apis mellifera unicolor (Hymenoptera: Apidae), the endemic honey bee from Madagascar

Hygienic behavior (HB) is one of the natural mechanisms of honey bee for limiting the spread of brood diseases and Varroa destructor parasitic mite. Objective of our study was to measure HB of Apis mellifera unicolor colonies (N = 403) from three geographic regions (one infested and two free of V. destructor) in Madagascar. The pin-killing method was used for evaluation of the HB. Responses were measured from 3 h 30 min to 7 h after perforation of the cells. Colonies were very effective in detecting perforated cells. In the first 4 h, on average, they detected at least 50% of the pin-killed brood. Six hours after cell perforation, colonies tested (N = 91) showed a wide range of uncapped (0 to 100%) and cleaned cells (0 to 82%). Global distribution of the rate of cleaned cells at 6 h was multimodal and hygienic responses could be split in three classes. Colonies from the three regions showed a significant difference in HB responses. Three hypotheses (geographic, genetic traits, presence of V. destructor) are further discussed to explain variability of HB responses among the regions. Levels of HB efficiency of A. mellifera unicolor colonies are among the greatest levels reported for A. mellifera subspecies. Presence of highly hygienic colonies is a great opportunity for future breeding program in selection for HB.

Genetic mapping of maize stripe disease resistance from the Mascarene source

Maize stripe virus (MStV) is a potentially threatening virus disease of maize in the tropics. We mapped quantitative trait loci (QTLs) controlling resistance to MStV in a maize population of 157 F(2:3) families derived from the cross between two maize lines, Rev81 (tropical resistant) and B73 (temperate susceptible). Resistance was evaluated under artificial inoculations in replicated screenhouse trials across different seasons in Réunion Island, France. Composite interval mapping was employed for QTL detection with a linkage map of 143 microsatellite markers. Heritability estimates across seasons were 0.96 and 0.90 for incidence and severity, respectively, demonstrating a high genotypic variability and a good control of the environment. Three regions on chromosomes 2L, 3 and 5, with major effects, and another region on chromosome 2S, with minor effects, provided resistance to MStV in Rev81. In individual seasons, the chr2L QTL explained 60-65% of the phenotypic variation for disease incidence and 21-42% for severity. The chr3 QTL, mainly associated with incidence and located near centromere, explained 42-57% of the phenotypic variation, whereas the chr5 QTL, mainly associated with severity, explained 26-53%. Overall, these QTLs explained 68-73% of the phenotypic variance for incidence and 50-59% for severity. The major QTLs on chr2 and 3 showed additive gene action and were found to be stable over time and across seasons. They also were found to be included in genomic regions with important clusters of resistance genes to diseases and pests. The major QTL on chr5 appeared to be partially dominant in favour of resistance. It was stable over time but showed highly significant QTL x season interactions. Possible implications of these QTLs in different mechanisms of resistance against the virus or the insect vector are discussed. The prospects for transferring these QTLs in susceptible maize cultivars and combining them with other resistances to virus diseases by conventional or marker-assisted breeding are promising.

A New Tomato leaf curl virus from Mayotte

In June 2003, symptoms of stunting and leaf curling resembling symptoms of tomato leaf curl disease, as well as reductions in yields, were observed on tomato plants in the western (Combani and Kahani) and eastern (Dembeni, Kaoueni, and Tsararano) regions of Mayotte, a French island in the Comoros Archipelago located in the northern part of the Mozambique Channel. The whitefly, Bemisia tabaci (Gennadius), was observed colonizing tomato plants and other vegetable crops at low levels. Overall, 13 leaf samples with symptoms were collected from tomato plants among the five regions and tested for the presence of begomoviruses using a polymerase chain reaction (PCR) assay with two sets of degenerate primers designed to amplify two regions of the A component of begomoviruses. Primers MP16 and MP82 amplify an approximately 500-bp fragment located between the intergenic conserved nonanucleotide sequence and the first 200 bp of the coat protein (CP) gene (2). Primers AV494 and AC1048 amplify the approximately 550-bp core region of the CP gene (3). Six leaf samples, one from Combani, three from Dembeni, and two from Kahani, gave a PCR product of the expected size with both sets of primers. No PCR products were obtained with degenerate primers designed for begomovirus DNA B or β. The approximately 500- and 550-bp PCR products from one sample each of Combani (EMBL Accession Nos. AJ620912 and AJ620915, respectively), Dembeni (EMBL Accession Nos. AJ620911 and AJ620914, respectively), and Kahani (EMBL Accession Nos. AJ620913 and AJ620916, respectively) were sequenced. For the 489-bp sequences obtained with the MP16/MP82 primer set, the three isolates had 90 to 95% nucleotide identity (DNAMAN; Lynnon BioSoft, Quebec). The most significant sequence alignments (NCBI and BLAST) were with begomoviruses; 80 to 83% nucleotide identity was obtained with the Tomato yellow leaf curl Morondava virus (TYLCMV) isolates from Madagascar (EMBL Accession Nos. AJ422123 and AJ422124), 80 to 82% nucleotide identity was obtained with the South African cassava mosaic virus (SACMV) isolates (GenBank and EMBL Accession Nos. AF155806 and AJ422132), and 79 to 81% nucleotide identity was obtained with the East African cassava mosaic Malawi virus (EMBL Accession No. AJ006460). For the 522-bp sequences obtained with the AV494/AC1048 primer set, 95 to 97% nucleotide identity was shown between the three isolates. The most significant sequence alignments were also with begomoviruses; TYLCMV isolate Morondava (EMBL Accession No. AJ422125) with 86 to 88% nucleotide identity, Tomato yellow leaf curl virus isolates (GenBank and EMBL Accession Nos. AF105975, AJ489258, AB014346, AF024715, AF071228, and X76319) with 86 to 87% nucleotide identity, and SACMV isolate M12 (EMBL Accession No. AJ422132) with 85 to 86% nucleotide identity. According to the current taxonomic criteria for the provisional classification of a new begomovirus species, nucleotide sequence identity in the core region of the CP <90% (1), the tomato begomovirus from Mayotte is a new species and is provisionally named Tomato leaf curl Mayotte virus. References: (1) J. K. Brown et al. Arch. Virol. 146:1581, 2001. (2) P. Umaharan et al. Phytopathology 88:1262, 1998. (3) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

First Molecular Identification of a Begomovirus Isolated from Tomato in Madagascar

In April 2001, reduced leaf size, leaf curling, yellowing symptoms, and reduced yield were observed in tomato plants in the southwestern (Toliary, Morondava, Miandrivazo) and northern (Antsiranana) regions of Madagascar. Symptoms were similar to those caused by Tomato yellow leaf curl virus (TYLCV, genus Begomovirus, family Geminiviridae). Large populations of Bemisia tabaci (Gennadius) were observed colonizing tomato, other crops, and weeds. Leaf samples were collected from tomato plants from 14 sites located in northern, central, and southern Madagascar. Two plant samples collected near Antsiranana, one sample near Morondava, and one sample near Toliary were positive in triple-antibody sandwich enzyme-linked immunosorbent assay using a begomovirus-specific antibody purchased from ADGEN (Nellies Gates, Auchincruive, Scotland, UK). A 500-bp product was amplified and cloned (2) from two leaf samples collected near Toliary and one near Morondava using a pair of degenerate primers that are expected to amplify a region of the A component of begomoviruses between the intergenic conserved nonanucleotide sequence and the first 200 nucleotides of the coat protein ORF. The sequences corresponding to the two Toliary samples (GenBank Accession Nos. AJ422123 and AJ422124) and the Morondava sample (GenBank No. AJ422125) showed the most significant alignments (NCBI, BLAST) with begomoviruses, Tobacco leaf curl virus from Zimbabwe (GenBank Accession No. AF 350330) and Tomato leaf curl virus from Tanzania (GenBank Accession No. U73498) with 76 to 77% nucleotide identity (Clustal method, MegAlign, DNASTAR, London) and South African cassava mosaic viruses (SACMV GenBank Accession Nos. AJ422132 and AF155806) and East African cassava mosaic viruses from Malawi (GenBank Accession Nos. AJ006459 and AJ006460) with 74 to 75.5% nucleotide identity. The low nucleotide identity suggests that the begomovirus isolated from tomato in Madagascar is a new species. Since the core region of the coat protein gene is a molecular marker for provisional classification of begomoviruses (1), this region was amplified for the Morondava isolate with degenerate primers. The 519nt core fragment obtained showed the most significant alignments with SACMV (GenBank Accession No. AF329227), Cassava geminivirus from Mozambique (GenBank Accession No. AF329240), and with TYLCV (GenBank Accession Nos. AB014346 and AF105975) with 81 to 82% nucleotide identity. According to the current taxonomic criteria (4), the begomovirus from Madagascar is a new one that is related to begomoviruses from the southern part of Africa and to TYLCV and is provisionally named Tomato yellow leaf curl Morondava virus (TYLCMV). Tomato yellow leaf curl disease was previously described in Madagascar by Reckhaus (3) who presumed that it was caused by TYLCV. Although symptoms in the tomato plant from which TYLCMV was isolated were similar to those induced by TYLCV, TYLCV was not detected in our samples. References: (1) J. K. Brown et al. Arch. Virol. 146:1581, 2001 (2) M. Peterschmitt et al. Plant Dis. 83:303, 1999. (3) P. Reckhaus, Maladies et ravageurs des cultures maraîchères: A l'exemple de Madagascar. GTZ, Weikersem, 1997. (4) M. H. V. van Regenmortel et al. Virus Taxonomy. Seventh Rep. Int. Comm. Taxon. Viruses. Academic Press, San Diego, 2000.