Molecular characterization of ' Candidatus Liberibacter' species/strains causing huanglongbing disease of citrus in Kenya

This study was undertaken to characterize the alpha subgroup of the proteobacteria causing the huanglongbing (HLB) disease of citrus from three different ecological zones of Kenya namely the Lower highlands (LH2, LH3, 1800-1900 m above sea level); Upper midlands (UM3, UM4, 1390-1475m), Lower midlands (LM5, LM4, LM3 of 1290-1340-1390m), by isolation and sequencing DNA encoding the L10 and L12 ribosomal proteins and the intergenic region. A 7I6-basepair DNA fragment was amplified and sequenced and consisted of 536 basepairs of DNA encoding the L10 protein, 44 basepairs of DNA intergenic region and 136 basepairs of DNA that partially encodes the L12 protein. Sequences of rpL10/L12 protein genes from Kenyan strains were 98% and 81% similar to the South African ' Candidatus Liberibacter africanus strain Nelspruit' and the Asian 'Candidatus Liberibacter asiaticus' strains, respectively. The intergenic rDNA sequence of Kenyan strain from UM and LM showed 84% similarity with 'Candidatus L. africanus strain Nelspruit' and 50% similarity with 'Candidatus L. asiaticus' strain. However, the LH strain had an 11- basepairs deletion, while the LM4 had a 5- basepair deletion in the intergenic region compared to 'Candidatus L. africanus strain Nelspruit'. The L10 amino acid sequence was 100% homologous among HLB bacteria obtained from the agro-ecological zones in Kenya and the L10 protein sequence was also homologus to 'Candidatus L. africanus strain Nelspruit'. Nevertheless, the L10 amino acid sequence of 'Candidatus L. asiaticus' and the 'Candidatus L. africanus subsp. capensis' differed from the Kenyan strains by 18.36% and 11.82%, respectively. Phylogenetic analysis of both the L10/L12 rDNA sequences and the L10 amino acid sequences clustered the Kenyan strains of the 'Candidatus Liberibacter' species with members of alpha subdivision of proteobacteria

Combining Ability For Earliness And Yield Among South Sudanese F1 Sorghum Genotypes

The development of staygreen genotypes through hybridization is an important food security strategy in the semi-arid tropics. This study used 36 sorghum synthetics obtained from a 6 x 6 full diallel mating design. The parents, F1 progenies and their reciprocals showed significant difference for days to flowering suggesting their diversity with regard to this triat. There were significant differences among the maternal and non-maternal effects implying that maternal genes play a greater role in regulating maturity. There were higher genetic predictability ratios for days to flowering, panicle weight and grain weight, suggesting that additive gene action played a bigger role than non-additive genes in the control of these traits. The study identified parental lines, ICSV III IN, B5 and Macia as exhibiting earliness that can be exploited in the breeding program for drought evading hybrids. Similarly, the F1 crosses B35 x Okabir, Lodoka x B35, Okabir x Macia, ICSV II IN x Macia, ICSV III IN x Akuorachot, Lodoka x Akuorachot and Lodoka x Okabir were identified as drought evading synthetics while F1 crosses, B35 x Akuorachot, B35 x Macia, Lodoka x B35, ICSV III IN x Macia, and Lodoka x Macia were identified as high yielding synthetics

Susceptibility of common weeds and cultivated crops in major maize growing agroecological zones of Uganda to viruses causing maize lethal necrosis disease

Maize lethal necrosis (MLN) disease is caused when maize plants become co-infected with Maize chlorotic mottle virus (MCMV) and potyviruses notably Sugarcane Mosaic Virus (SCMV). Apart from maize, little is known about susceptibility of weed species and cultivated crop species usually growing in proximity with maize to MLN viruses in Uganda. The common weeds and crop plants were mechanically inoculated with combined sap from MCMV and SCMV infected maize plants. Samples were tested for MLN causing viruses by Double Antibody Sandwich Enzyme-Linked Immunosorbent Assay (DAS-ELISA) and Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). The weeds that were susceptible to MCMV were Digitaria abyssinica, Eleusine africana and Roetboellia cochinchinensis; while those susceptible to SCMV were Pennisetum purpureum, Panicum maximum and Roetboellia cochinchinensis. The cultivated crops were susceptible only to MCMV and included cassava (Manihot esculenta), groundnut (Arachis hypogaea) and bean (Phaseolus vulgaris). Common weeds and cultivated crops growing close to maize in Uganda have differential susceptibility to MLN causing viruses and can act as reservoirs of MLN causing viruses. It is critical to identify non-MLN hosts in cultivated crops for crop rotation and early weeding to reduce on MLN virus inoculum in cropping syste

Rapid epidemic expansion of the SARS-CoV-2 Omicron variant in southern Africa

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic in southern Africa has been characterised by three distinct waves. The first was associated with a mix of SARS-CoV-2 lineages, whilst the second and third waves were driven by the Beta and Delta variants, respectively1-3. In November 2021, genomic surveillance teams in South Africa and Botswana detected a new SARS-CoV-2 variant associated with a rapid resurgence of infections in Gauteng Province, South Africa. Within three days of the first genome being uploaded, it was designated a variant of concern (Omicron) by the World Health Organization and, within three weeks, had been identified in 87 countries. The Omicron variant is exceptional for carrying over 30 mutations in the spike glycoprotein, predicted to influence antibody neutralization and spike function4. Here, we describe the genomic profile and early transmission dynamics of Omicron, highlighting the rapid spread in regions with high levels of population immunity

The evolving SARS-CoV-2 epidemic in Africa: insights from rapidly expanding genomic surveillance

Investment in SARS-CoV-2 sequencing in Africa over the past year has led to a major increase in the number of sequences generated, now exceeding 100,000 genomes, used to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence domestically, and highlight that local sequencing enables faster turnaround time and more regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and shed light on the distinct dispersal dynamics of Variants of Concern, particularly Alpha, Beta, Delta, and Omicron, on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve, while the continent faces many emerging and re-emerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance.

Investment in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing in Africa over the past year has led to a major increase in the number of sequences that have been generated and used to track the pandemic on the continent, a number that now exceeds 100,000 genomes. Our results show an increase in the number of African countries that are able to sequence domestically and highlight that local sequencing enables faster turnaround times and more-regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and illuminate the distinct dispersal dynamics of variants of concern-particularly Alpha, Beta, Delta, and Omicron-on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve while the continent faces many emerging and reemerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century