A novel East African monopartite begomovirus-betasatellite complex that infects Vernonia amygdalina

The complete genomes of a monopartite begomovirus (genus Begomovirus, family Geminiviridae) and an associated betasatellite found infecting Vernonia amygdalina Delile (family Compositae) in Uganda were cloned and sequenced. Begomoviruses isolated from two samples showed the highest nucleotide sequence identity (73.1% and 73.2%) to an isolate of the monopartite begomovirus tomato leaf curl Vietnam virus, and betasatellites from the same samples exhibited the highest nucleotide sequence identity (67.1% and 68.2%) to vernonia yellow vein Fujian betasatellite. Following the current taxonomic criteria for begomovirus species demarcation, the isolates sequenced here represent a novel begomovirus species. Based on symptoms observed in the field, we propose the name vernonia crinkle virus (VeCrV) for this novel begomovirus and vernonia crinkle betasatellite (VeCrB) for the associated betasatellite. This is the first report of a monopartite begomovirus-betasatellite complex from Uganda

Desmodium mottle virus, the first legumovirus (genus Begomovirus) from East Africa

A novel bipartite legumovirus (genus Begomovirus, family Geminiviridae), that naturally infects the wild leguminous plant Desmodium sp. in Uganda, was molecularly characterized and named Desmodium mottle virus. The highest nucleotide identities for DNA-A, obtained from two field-collected samples, were 79.9% and 80.1% with the legumovirus, soybean mild mottle virus. DNA-B had the highest nucleotide identities (65.4% and 66.4%) with a typical non-legumovirus Old World begomovirus, African cassava mosaic virus. This is the first report of a legumovirus in East Africa and extends the known diversity of begomoviruses found infecting wild plants in this continent

Evidencia de variabilidad molecular de begomovirus que afectan el cultivo de frijol (Phaseolus vulgaris) en Cuba

Las epifitias causadas por geminivirus son un factor limitante para la productividad de los cultivos de frijol y de soya en Cuba. La detección y la caracterización de los agentes causales es una necesidad para el manejo de estas enfermedades. Desde la década de los setenta del pasado siglo se ha podido evidenciar en Cuba una emergencia de enfermedades virales en plantaciones de frijol común. Durante las campañas de producción 2012-2015 se ha comenzado a observar una diversidad de síntomas asociados a la presencia de poblaciones de mosca blanca, debido a la alta tasa de mutaciones y al intercambio genético que presentan los geminivirus como mecanismos evolutivos. En este trabajo se colectaron muestras con síntomas diferenciales en varias localidades productoras, se realizaron extracciones de ADN, las que se amplificaron mediante el sistema de círculo rodante. Los genomas circulares amplificados fueron digeridos con diferentes combinaciones de enzimas de restricción. Los resultados revelaron diversos patrones polimórficos, los cuales pueden estar asociados a la presencia de especies de begomovirus no informadas previamente en el país, tanto en infecciones simples como en concomitantes. En el trabajo se discuten los resultados relacionados con la diversidad de especies presentes y la presencia de infecciones mixtas

Plant resistance to geminiviruses

Geminiviruses cause major damage to crop plants and evolve through mutations, recombination and pseudo-recombination, expanding their host range and becoming pandemic due to international trade and invasive vector species. Management of geminiviruses consists of breeding resistant crops by employing natural resistance genes from different cultivated or related wild plant species. Compared to other plant viruses, such as potyviruses, the information on resistance genes/loci identified for geminiviruses is scarce. Other strategies have been developed based on the virus genome; however, these have not yet reached the commercial field. Here we catalog and describe the resistance genes/loci identified against the most important geminiviruses, in the most economically important crops they infect: cassava, tomato, bean, maize and cotton.Peer reviewe

A comprehensive framework for the delimitation of species within the Bemisia tabaci cryptic complex, a global pest-species group

Identifying cryptic species poses a substantial challenge to both biologists and naturalists due to morphological similarities. Bemisia tabaci is a cryptic species complex containing more than 44 putative species; several of which are currently among the world’s most destructive crop pests. Interpreting and delimiting the evolution of this species complex has proved problematic. To develop a comprehensive framework for species delimitation and identification, we evaluated the performance of distinct data sources both individually and in combination among numerous samples of the B. tabaci species complex acquired worldwide. Distinct datasets include full mitogenomes, single-copy nuclear genes, restriction site-associated DNA sequencing, geographic range, host speciation, and reproductive compatibility datasets. Phylogenetically, our well-supported topologies generated from three dense molecular markers highlighted the evolutionary divergence of species of the B. tabaci complex and suggested that the nuclear markers serve as a more accurate representation of B. tabaci species diversity. Reproductive compatibility datasets facilitated the identification of at least 17 different cryptic species within our samples. Native geographic range information provides a complementary assessment of species recognition, while the host range datasets provide low rate of delimiting resolution. We further summarized different data performances in species classification when compared with reproductive compatibility, indicating that combination of mtCOI divergence, nuclear markers, geographic range provide a complementary assessment of species recognition. Finally, we represent a model for understanding and untangling the cryptic species complexes based on the evidence from this study and previously published articles

Comparative evolutionary analyses of eight whitefly Bemisia tabaci sensu lato genomes: cryptic species, agricultural pests and plant-virus vectors

The genomes, transcriptomes, and predicted protein-coding sequences are available from Ensembl Metazoa (http://metazoa.ensembl.org) and are included within the references. Raw RNA-Seq datasets generated and/or analyzed during the current study are available from the European Nucleotide Archive database repository (https://www.ebi.ac.uk/ena) under the parent project accessions: PRJEB28507, PRJEB36965, PRJEB35304, PRJEB39408. All data generated during the analyses of these datasets are included in this published article, supplementary information files, and figshare repository (https://doi.org/10.6084/m9.figshare.23666799; https://doi.org/10.6084/m9.figshare.23666832.v4; https://doi.org/10.6084/m9.figshare.23666844).International audienceBackground: The group of > 40 cryptic whitefly species called Bemisia tabaci sensu lato are amongst the world's worst agricultural pests and plant-virus vectors. Outbreaks of B. tabaci s.l. and the associated plant-virus diseases continue to contribute to global food insecurity and social instability, particularly in sub-Saharan Africa and Asia. Published B. tabaci s.l. genomes have limited use for studying African cassava B. tabaci SSA1 species, due to the high genetic divergences between them. Genomic annotations presented here were performed using the 'Ensembl gene annotation system' , to ensure that comparative analyses and conclusions reflect biological differences, as opposed to arising from different methodologies underpinning transcript model identification. Results: We present here six new B. tabaci s.l. genomes from Africa and Asia, and two re-annotated previously published genomes, to provide evolutionary insights into these globally distributed pests. Genome sizes ranged between 616-658 Mb and exhibited some of the highest coverage of transposable elements reported within Arthropoda. Many fewer total protein coding genes (PCG) were recovered compared to the previously published B. tabaci s.l. genomes and structural annotations generated via the uniform methodology strongly supported a repertoire of between 12.8-13.2 × 10 3 PCG. An integrative systematics approach incorporating phylogenomic analysis of nuclear and mitochondrial markers supported a monophyletic Aleyrodidae and the basal positioning of B. tabaci Uganda-1 to the sub-Saharan group of species. Reciprocal cross-mating data and the co-cladogenesis pattern of the primary obligate endosymbiont 'Candidatus Portiera aleyrodidarum' from 11 Bemisia genomes further supported the phylogenetic reconstruction to show that African cassava B. tabaci populations consist of just three biological species. We include comparative analyses of gene families related to detoxification, sugar metabolism, vector competency and evaluate the presence and function of horizontally transferred genes, essential for understanding the evolution and unique biology of constituent B. tabaci. s.l species.Conclusions: These genomic resources have provided new and critical insights into the genetics underlying B. tabaci s.l. biology. They also provide a rich foundation for post-genomic research, including the selection of candidate gene-targets for innovative whitefly and virus-control strategies