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Achromobacter xylosoxidans is one of the nitrogen-fixing bacteria associated with cowpea rhizosphere across Africa. Although its role in improving soil fertility and inducing systemic resistance in plants against pathogens has been documented, there is limited information on its complete genomic characteristics from cowpea roots. Here, we report the complete genome sequence of A. xylosoxidans strain DDA01 isolated from the topsoil of a field where cowpea plants tolerant to cucumber mosaic virus (CMV) were grown in Ibadan, Nigeria. The genome of DDA01 was sequenced via Illumina MiSeq and contained 6,930,067 nucleotides with 67.55% G + C content, 73 RNAs, 59 tRNAs, and 6421 protein-coding genes, including those associated with nitrogen fixation, phosphate solubilization, Indole3-acetic acid production, and siderophore activity. Eleven genetic clusters for secondary metabolites, including alcaligin, were identified. The potential of DDA01 as a plant growth-promoting bacteria with genetic capabilities to enhance soil fertility for resilience against CMV infection in cowpea is discussed. To our knowledge, this is the first complete genome of diazotrophic bacteria obtained from cowpea rhizosphere in sub-Saharan Africa, with potential implications for improved soil fertility, plant disease resistance, and food security., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The study was conducted to characterise bean common mosaic virus strain Blackeye (BCMV-BICM) and determine the likelihood of seed transmission in cowpea breeding lines. F6 cowpea lines obtained from crosses between 'Ife-Brown' and 'IT-95 K-193-12' were planted at five locations in Southwest Nigeria for multilocational evaluation. Virus symptoms were observed on leaves of the breeding lines planted in Ibadan at eight weeks after planting. Enzyme-linked immunosorbent assay (ELISA) was used to determine the presence of six viruses: BCMV-BICM, cowpea aphid-borne mosaic virus, cucumber mosaic virus, cowpea mottle virus, southern bean mosaic virus and cowpea mild mottle virus. Seed transmission tests were carried out to determine virus transmission by seeds while growth and yield components of the cowpea lines were obtained. Reverse transcription polymerase chain reaction, sequencing and phylogenetic analyses were also used to characterise the BCMV-BICM isolates. The observed symptoms, leaf curling and mosaics, were typical of BCMV-BICM infection and ELISA results confirmed the presence of only BCMV-BICM. Line 'L-22-B' had the highest yield of 1653.9 kgha -1 followed by 'L-43-A' (1072 kgha -1 ). A non-significant relationship existed between the virus and germination parameters and similarly, the relationship between virus titres and yield parameters was not significant. Sequence analysis of the virus coat protein (CP) gene revealed the presence of three isolates with 96.87-97.47% nucleotide and 98.2-98.65% amino acid similarities and a 99.10-99.55% match with BCMV-BICM CP genes in GenBank. The deduced CP gene sequences showed unique changes at specific sites, while phylogenetic inferences revealed at least two separate origins for the isolates. Seed transmission is evident in all the cowpea breeding lines and 'L-22-B' and 'L-43-A' showed significant tolerance to BCMV-BICM. Thus, it is recommended that seeds from infected fields should not be used for further planting to prevent the introduction of viruses into new areas where their effect could be devastating in susceptible lines., Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00812-3., Competing Interests: Conflict of interestThe authors declare that they have no conflicts of interest., (© The Author(s), under exclusive licence to Indian Virological Society 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.)

Cucumber mosaic virus (CMV, Bromoviridae : Cucummovirus ), one of the most widespread plant viruses with several hosts, causes huge losses in yield quality and quantity. The occurrence of various CMV strains and high genetic diversity within the virus complicate its management. We describe the population structure of CMV in Nigeria using partial RNA1 and RNA3 gene sequences from three natural hosts: pepper ( Capsicum annuum ), tomato ( Solanum lycopersicum ), and watermelon ( Citrullus lanatus ). One hundred and six leaf samples were obtained from 16 locations across Nigeria, and specific primers were used to amplify the two gene fragments using PCR. Twenty-four samples tested positive for CMV using RNA1 primers, and amplicons were sequenced from 12 isolates, revealing 82.94-99.80% nucleotide and 85.42-100% amino acid sequence similarities within the population. The partial RNA3 fragment, corresponding to the complete coat protein (CP) gene, was sequenced from seven isolates, with 95.79-97.90% and 98.62-100% nucleotide and amino acid intrapopulation similarities, respectively. The isolates belonged to subgroup IB and formed distinct phylogenetic clusters in both gene sets, indicating putative novel strains. Recombination signals, supported by phylogenetic inferences, were detected within the RNA1 dataset ( P ≤ 0.05) and identified a recombinant isolate within the Nigerian sequences. No recombination was detected within the CP genes. Population genetics parameters established high diversity within the Nigerian population compared to other isolates worldwide, while selection pressure estimates revealed the existence of negative selection in both gene sets. Although CMV subgroup IB strains were postulated to originate from Asia, this study reveals their prevalence across several hosts from different locations in Nigeria. To our knowledge, this is the first comprehensive description of a recombinant CMV subgroup IB isolate from West Africa, which has implications for its robust detection and overall management., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Apalowo, Adediji, Balogun, Fakolujo, Archibong, Izuogu, Abdelgawad, Ghoneim, Mustapha, Qashqari, Batiha and Atiri.)

Background: Tomato production is threatened worldwide by the occurrence of begomoviruses which are associated with tomato leaf curl diseases. There is little information on the molecular properties of tomato begomoviruses in Kenya, hence we investigated the population and genetic diversity of begomoviruses associated with tomato leaf curl in Kenya., Methods: Tomato leaf samples with virus-like symptoms were obtained from farmers' field across the country in 2018 and Illumina sequencing undertaken to determine the genetic diversity of associated begomoviruses. Additionally, the occurrence of selection pressure and recombinant isolates within the population were also evaluated., Results: Twelve complete begomovirus genomes were obtained from our samples with an average coverage of 99.9%. The sequences showed 95.7-99.7% identity among each other and 95.9-98.9% similarities with a Tomato leaf curl virus Arusha virus (ToLCArV) isolate from Tanzania. Analysis of amino acid sequences showed the highest identities in the regions coding for the coat protein gene (98.5-100%) within the isolates, and 97.1-100% identity with the C4 gene of ToLCArV. Phylogenetic algorithms clustered all Kenyan isolates in the same clades with ToLCArV, thus confirming the isolates to be a variant of the virus. There was no evidence of recombination within our isolates. Estimation of selection pressure within the virus population revealed the occurrence of negative or purifying selection in five out of the six coding regions of the sequences., Conclusions: The begomovirus associated with tomato leaf curl diseases of tomato in Kenya is a variant of ToLCArV, possibly originating from Tanzania. There is low genetic diversity within the virus population and this information is useful in the development of appropriate management strategies for the disease in the country.

Maize streak virus disease (MSVD), caused by Maize streak virus (MSV; genus Mastrevirus), is one of the most severe and widespread viral diseases that adversely reduces maize yield and threatens food security in Africa. An effective control and management of MSVD requires robust and sensitive diagnostic tests capable of rapid detection of MSV. In this study, a loop-mediated isothermal amplification (LAMP) assay was designed for the specific detection of MSV. This test has shown to be highly specific and reproducible and able to detect MSV in as little as 10 fg/µl of purified genomic DNA obtained from a MSV-infected maize plant, a sensitivity 10 5 times higher to that obtained with polymerase chain reaction (PCR) in current general use. The high degree of sequence identity between Zambian and other African MSV isolates indicate that this LAMP assay can be used for detecting MSV in maize samples from any region in Africa. Furthermore, this assay can be adopted in minimally equipped laboratories and with potential use in plant clinic laboratories across Africa strengthening diagnostic capacity in countries dealing with MSD.

High-throughput sequence analysis revealed the complete genome sequence of a novel, hitherto uncharacterized strain of Chickpea chlorotic dwarf virus (CpCDV) from tomato plants in Kenya. The sequence shared its highest nucleotide similarity (88.7%) with two CpCDV isolates from Burkina Faso., (Copyright © 2020 Avedi et al.)