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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. [ABSTRACT FROM AUTHOR]

The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a worldwide pest and a vector of numerous plant viruses. B. tabaci is composed of dozens of morphologically indistinguishable biotypes and its taxonomic status is still controversial. This phloem-feeder harbours the primary symbiont Portiera aleyrodidarum and potentially six secondary symbionts: Cardinium, Arsenophonus, Hamiltonella, Rickettsia, Wolbachia and Fritschea. In the southwest Indian Ocean, La Réunion hosts two biotypes of this species: B (invasive) and Ms (indigenous). A multiplex PCR was developed to study the symbiont community of B. tabaci on La Réunion. Symbiont community prevalence and composition, host mitochondrial and nuclear genetic diversity, as well as host plant and localization, were described on field populations of La Réunion for B and Ms B. tabaci biotypes and their hybrids. A clear association between symbiotypes and biotypes was shown. Cardinium, Arsenophonus and Rickettsia were found in the Ms biotype (73.6%, 64.2% and 3.3%, respectively). Hamiltonella (exclusively) and Rickettsia were found in the B biotype (78% and 91.2%, respectively). Hybrids harboured all symbiotypes found in Ms and B populations, but with a higher prevalence of Ms symbiotypes than expected under random hybridization. An unexpected majority was Cardinium mono-infected (65.6%), and a striking minority (9%) harboured Cardinium/ Arsenophonus. In the hybrids only, genetic diversity was linked to symbiotype. Among the hybrids, significant links were found between symbiotypes and: (i) mitochondrial COI sequences, i.e. maternal origin; and (ii) alleles of nuclear microsatellite loci, specific to either Ms or B parental biotype. Taken together, our results suggest that Cardinium and/or Arsenophonus may manipulate the reproduction of indigenous (Ms) with invasive (B) biotypes of Bemisia tabaci. [ABSTRACT FROM AUTHOR]

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 F2:3 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 × 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. [ABSTRACT FROM AUTHOR]

The article discusses the result of a survey of plants showing virus disease symptoms. The survey, which was conducted in the Seychelles archipelago on Mahé island, made analysis on leaf curling symptoms of several plants found out the presence of a new leaf curl virus. The virus was found in the tomato leaf extract that was analyzed using two sets of degenerate primers to detect the presence of begomoviruses by polymerase chain reaction (PCR). The newly identified virus is named Tomato leaf curl Seychelles virus (ToLCSCV).

The article reports on the occurrence of Tomato chlorosis virus (ToCV) on tomato in Réunion Island in Madagascar. Yellow-leaf symptoms include chlorotic mottling, and the interveinal areas of leaves developed red or brown necrotic flecks. Around 20 leaf samples with symptoms were gathered from tomato plants, and total RNA was extracted from these samples. Sequences obtained from the samples had 99.5% nucleotide identity when aligned. The most significant sequence alignments were 98% with ToCV isolates.

The article discusses the presence of both recombinant and non-recombinant strains of Tomato yellow leaf curl virus on tomato in Réunion Island. In April 2004, severe symptoms of stunting, yellowing and leaf curling, resembling the symptoms of tomato yellow leaf curl disease, were observed on tomato plants in Saint Gilles in the north-west region of Réunion. Twenty-two leaf samples from affected tomato plants were collected and tested for the presence of begomoviruses using a PCR assay. All the leaf samples produced PCR products of the expected size with both sets of primers.