scholarly journals First Report of East African Cassava Mosaic Begomovirus in Nigeria

Plant Disease ◽  
1999 ◽  
Vol 83 (4) ◽  
pp. 398-398 ◽  
Author(s):  
F. O. Ogbe ◽  
G. I. Atiri ◽  
D. Robinson ◽  
S. Winter ◽  
A. G. O. Dixon ◽  
...  
Keyword(s):  
Central Africa ◽  
Mosaic Disease ◽  
Sub Saharan Africa ◽  
Cassava Mosaic Disease ◽  
Enzyme Linked Immunosorbent Assay ◽  
East African ◽  
African Countries ◽  
Manihot Esculenta Crantz ◽  
Cross River State ◽  
Sub Saharan

Cassava (Manihot esculenta Crantz) is an important food crop in sub-Saharan Africa. One of the major production constraints is cassava mosaic disease caused by African cassava mosaic (ACMV) and East African cassava mosaic (EACMV) begomoviruses. ACMV is widespread in its distribution, occurring throughout West and Central Africa and in some eastern and southern African countries. In contrast, EACMV has been reported to occur mainly in more easterly areas, particularly in coastal Kenya and Tanzania, Malawi, and Madagascar. In 1997, a survey was conducted in Nigeria to determine the distribution of ACMV and its strains. Samples from 225 cassava plants showing mosaic symptoms were tested with ACMV monoclonal antibodies (MAbs) in triple antibody sandwich enzyme-linked immunosorbent assay (1). Three samples reacted strongly with MAbs that could detect both ACMV and EACMV. One of them did not react with ACMV-specific MAbs while the other two reacted weakly with such MAbs. With polymerase chain reaction (2), the presence of EACMV and a mixture of EACMV and ACMV in the respective samples was confirmed. These samples were collected from two villages: Ogbena in Kwara State and Akamkpa in Cross River State. Co-infection of some cassava varieties with ACMV and EACMV leads to severe symptoms. More importantly, a strain of mosaic geminivirus known as Uganda variant arose from recombination between the two viruses (2). This report provides evidence for the presence of EACMV in West Africa. References: (1) J. E. Thomas et al. J. Gen. Virol. 67:2739, 1986. (2) X. Zhou et al. J. Gen. Virol. 78:2101, 1997.

scholarly journals Genetic diversity and phylogeography of cassava mosaic viruses in Kenya

2006 ◽  
Vol 87 (10) ◽  
pp. 3053-3065 ◽  
Author(s):  
Simon E. Bull ◽  
Rob W. Briddon ◽  
William S. Sserubombwe ◽  
Kahiu Ngugi ◽  
Peter G. Markham ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Central Africa ◽  
Mosaic Disease ◽  
Sub Saharan Africa ◽  
African Cassava Mosaic Virus ◽  
Cassava Mosaic Disease ◽  
Polymorphism Analysis ◽  
Virus Species ◽  
East African ◽  
Virus Diversity

Cassava is a major factor in food security across sub-Saharan Africa. However, the crop is susceptible to losses due to biotic stresses, in particular to viruses of the genus Begomovirus (family Geminiviridae) that cause cassava mosaic disease (CMD). During the 1990s, an epidemic of CMD severely hindered cassava production across eastern and central Africa. A significant influence on the appearance of virus epidemics is virus diversity. Here, a survey of the genetic diversity of CMD-associated begomoviruses across the major cassava-growing areas of Kenya is described. Because an initial PCR-restriction fragment-length polymorphism analysis identified a much greater diversity of viruses than assumed previously, representative members of the population were characterized by sequence analysis. The full-length sequences of 109 components (68 DNA-A and 41 DNA-B) were determined, representing isolates of East African cassava mosaic virus and East African cassava mosaic Zanzibar virus, as well as a novel begomovirus species for which the name East African cassava mosaic Kenya virus is proposed. The DNA-B components were much less diverse than their corresponding DNA-A components, but nonetheless segregated into western and eastern (coastal) groups. All virus species and strains encountered showed distinct geographical distributions, highlighting the importance of preventing both the movement of viruses between these regions and the importation of the disease from adjacent countries and islands in the Indian Ocean that would undoubtedly encourage further diversification.

scholarly journals Evaluation of Cassava Genotypes for Agronomic Performance, Correlation with CMD and CBSD Parameters and Stability across Alupe, Kakamega and Kibos in Western Kenya

2020 ◽  
pp. 47-62
Author(s):  
L. N. Navangi ◽  
S. M. Githiri ◽  
E. M. Ateka ◽  
E. Kanju ◽  
T. L. Munga ◽  
...  
Keyword(s):  
Negative Relationship ◽  
Mosaic Disease ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Cassava Mosaic Disease ◽  
Agronomic Performance ◽  
Manihot Esculenta Crantz ◽  
Western Kenya ◽  
Local Standard ◽  
Sub Saharan

Cassava (Manihot esculenta Crantz) production in sub-Saharan Africa (SSA) is constrained by the two biotic constraints namely, cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The aim of this study was to evaluate elite cassava genotypes for variation in agronomical traits, correlate them to CMD and CBSD parameters and identify stable genotypes in Alupe, Kakamega and Kibos in Western Kenya. Twenty three (23) elite cassava genotypes that had shown resistance to either one or both of CMD and CBSD in Eastern Africa were evaluated. The trial was conducted using an alpha lattice balanced design with twenty three (23) genotypes, replicated three times at Alupe, Kakamega and Kibos in Western Kenya for an extended cropping cycle between 2016 and 2017. Results showed significant differences (P ≤ 0.05) between genotypes and location (or agro-ecology), but not interaction (P ≥ 0.05), for all the agronomic performance parameters evaluated. All the 23 cassava genotypes evaluated across the three locations had mean cyanide potential levels ranging from of 3.00–6.00 and were therefore, sweet and not bitter. The significant but negative relationship between CMD and CBSD incidence and severity with agronomic performance implied that their relationship was inverse. Confirmation of stability for agronomic performance was achieved through AMMI analysis, using AMMI stability value (ASV). Stable genotypes based on AMMI stability values (ASV) for fresh root yield across Alupe, Kakamega and Kibos were KBH/2002/066, Kibandameno (a local standard check), NASE-18, Kizimbani and NASE-3. These genotypes need to be further evaluated in more environments to assess their wider adaptability and stability.

scholarly journals Spatial Analysis of Temporal Changes in the Pandemic of Severe Cassava Mosaic Disease in Northwestern Tanzania

2017 ◽  
Vol 107 (10) ◽  
pp. 1229-1242 ◽  
Author(s):  
A. M. Szyniszewska ◽  
C. Busungu ◽  
S. B. Boni ◽  
R. Shirima ◽  
H. Bouwmeester ◽  
...  
Keyword(s):  
Mosaic Disease ◽  
Sub Saharan Africa ◽  
African Cassava Mosaic Virus ◽  
Cassava Mosaic Disease ◽  
East African ◽  
Northwestern Tanzania ◽  
Direction Of Movement ◽  
Vector Borne ◽  
Sub Saharan ◽  
Associated Variables

To improve understanding of the dynamics of the cassava mosaic disease (CMD) pandemic front, geospatial approaches were applied to the analysis of 3 years’ data obtained from a 2-by-2° (approximately 222-by-222 km) area of northwestern Tanzania. In total, 80 farmers’ fields were assessed in each of 2009, 2010, and 2011, with 20 evenly distributed fields per 1-by-1° quadrant. CMD-associated variables (CMD incidence, CMD severity, vector-borne CMD infection, and vector abundance) increased in magnitude from 2009 to 2010 but showed little change from 2010 to 2011. Increases occurred primarily in the two westernmost quadrants of the study area. A pandemic “front” was defined by determining the values of CMD incidence and whitefly abundance where predicted disease gradients were greatest. The pandemic-associated virus (East African cassava mosaic virus-Uganda) and vector genotype (Bemisia tabaci sub-Saharan Africa 1–subgroup 1) were both present within the area bounded by the CMD incidence front but both also occurred ahead of the front. The average speed and direction of movement of the CMD incidence front (22.9 km/year; southeast) and whitefly abundance front (46.6 km/year; southeast) were calculated, and production losses due to CMD were estimated to range from US$4.3 million to 12.2 million.

Tanzania: Civil–Military Relations and Nationalism

2020 ◽  
Author(s):  
Daniel G. Zirker
Keyword(s):  
Civil Society ◽  
Military Training ◽  
Sub Saharan Africa ◽  
East African ◽  
African Countries ◽  
Civil Military Relations ◽  
Sub Saharan ◽  
The 1960S ◽  
Military Relations ◽  
The Military

Why have there been no successful military interventions or civil wars in Tanzania’s nearly 60 years of independence? This one historical accomplishment, by itself striking in an African context, distinguishes Tanzania from most of the other post-1960 independent African countries and focuses attention on the possibilities and nature of successful civil–military relations in sub-Saharan Africa. Contrary to most civil–military relations theory, rather than isolating the military in order to achieve civilian oversight, Tanzania integrated the military, the dominant political party, and civil society in what one observer called a combination of “political militancy” and “antimilitarism,” somewhat akin, perhaps, to the Chinese model. China did provide intensive military training for the Tanzanians beginning in the 1960s, although this could in no way have been expected to ensure successful integration of the military with civil society, nor could it ensure peaceful civil–military relations. Eight potentially causal and overlapping conditions have been outlined to explain this unique absence of civil–military strife in an African country. Relevant but admittedly partial explanations are: the largely salutary and national developmental role of the founding president, Julius Nyerere; the caution and long-term fear of military intervention engendered by the 1964 East African mutinies; Tanzania’s radical foreign policy as a Frontline State; its ongoing territorial disputes with Uganda and Malawi; concerted efforts at coup-proofing through the co-opting of senior military commanders; and the country’s striking ethnic heterogeneity, in which none of the 125 plus ethnolinguistic tribes had the capacity to assume a hegemonic dominance. Each factor has a role in explaining Tanzania’s unique civil–military history, and together they may comprise a plausible explanation of the over 50 years of peaceful civil–military relations. They do not, however, provide a hopeful prognosis for future civil–military relations in a system that is increasingly challenging the dominant-party state, nor do they account for Tanzania’s subsequent democratic deficit.

scholarly journals COVID-19 Response in Sub-Saharan Africa: Lessons From Uganda

2020 ◽  
Vol 14 (3) ◽  
pp. e46-e48 ◽  
Author(s):  
Ivan Lumu
Keyword(s):  
Decision Making ◽  
Ebola Virus ◽  
Virus Disease ◽  
Sub Saharan Africa ◽  
Disease Spread ◽  
East African ◽  
Limited Disease ◽  
African Countries ◽  
Response Team ◽  
Sub Saharan

ABSTRACTThe prolongation of the Ebola epidemic may have allowed some countries to prepare and respond to the coronavirus disease (COVID-19) outbreak. In Uganda, the surveillance structure built for Ebola virus disease (EVD) has become a pillar in the COVID-19 response. This testing and tracing apparatus has limited disease spread to clusters with zero mortality compared with the neighboring East African countries. As more sub-Saharan countries implement social distancing to contain the outbreak, the interventions should be phased and balanced with health risk and socioeconomic situation. However, having a decision-making matrix would better guide the response team. These initial lessons from EVD-experienced Uganda may be helpful to other countries in the region.

scholarly journals Genetic Diversity of Mitochondrial DNA of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) Associated with Cassava and the Occurrence of Cassava Mosaic Disease in Zambia

Insects ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 761
Author(s):  
Patrick Chiza Chikoti ◽  
Mathias Tembo ◽  
James Peter Legg ◽  
Rudolph Rufini Shirima ◽  
Habibu Mugerwa ◽  
...  
Keyword(s):  
Bemisia Tabaci ◽  
Control Strategies ◽  
Mosaic Disease ◽  
Sub Saharan Africa ◽  
Cassava Mosaic Disease ◽  
Northern Province ◽  
Western Province ◽  
Key Factor ◽  
Sub Saharan ◽  
Brown Streak

Bemisia tabaci is an important vector of cassava brown streak viruses and cassava mosaic begomoviruses, the causal agents of cassava brown streak disease and cassava mosaic disease (CMD), respectively. A study was carried out to determine the genetic variability of B. tabaci associated with cassava and the occurrence of CMD in Zambia in 2013 and 2015. Phylogenetic analysis showed the presence of only the sub-Saharan Africa 1 (SSA1) genetic group in Zambia. The SSA1 population had three population subgroups (SGs): SSA1-SG1, SSA1-SG2 and SSA1-SG3. All three SSA1 population subgroups occurred in Western Province. However, only SSA1-SG3 occurred in Eastern Province, while only SSA1-SG1 occurred in North Western and Luapula Provinces. Adult B. tabaci were most abundant in Western Province in 2013 (11.1/plant) and 2015 (10.8/plant), and least abundant (0.2/plant) in Northern Province in both 2013 and 2015. CMD was prevalent in all seven provinces surveyed, with the highest incidence recorded in Lusaka Province in both 2013 (78%) and 2015 (83.6%), and the lowest in Northern Province in both 2013 (26.6%) and 2015 (29.3%). Although SSA1-SG1 occurred at greater abundances than the other subgroups, there was no direct association demonstrated between whitefly subgroup and incidence of CMD. Establishing which B. tabaci genetic groups and populations are associated with CMD and their distribution in the country is a key factor in guiding the development of CMD control strategies for cassava-dependent households.

scholarly journals Validation of high rates of nucleotide substitution in geminiviruses: phylogenetic evidence from East African cassava mosaic viruses

2009 ◽  
Vol 90 (6) ◽  
pp. 1539-1547 ◽  
Author(s):  
Siobain Duffy ◽  
Edward C. Holmes
Keyword(s):  
Nucleotide Substitution ◽  
Central Africa ◽  
Mosaic Disease ◽  
African Cassava Mosaic Virus ◽  
Cassava Mosaic Disease ◽  
East African ◽  
Substitution Rates ◽  
Leaf Curl Virus ◽  
Intensive Sampling ◽  
Major Pathogens

Whitefly-transmitted geminiviruses are major pathogens of the important crop cassava in Africa. The intensive sampling and sequencing of cassava mosaic disease-causing viruses that occurred in the wake of a severe outbreak in Central Africa (1997–2002) allowed us to estimate the rate of evolution of this virus. East African cassava mosaic virus and related species are obligately bipartite (DNA-A and DNA-B segments), and these two genome segments have different evolutionary histories. Despite these phylogenetic differences, we inferred high rates of nucleotide substitution in both segments: mean rates of 1.60×10−3 and 1.33×10−4 substitutions site−1 year−1 for DNA-A and DNA-B, respectively. While similarly high substitution rates were found in datasets free of detectable recombination, only that estimated for the coat protein gene (AV1), for which an additional DNA-A sequence isolated in 1995 was available, was statistically robust. These high substitution rates also confirm that those previously estimated for the monopartite tomato yellow leaf curl virus (TYLCV) are representative of multiple begomoviruses. We also validated our rate estimates by comparing them with those depicting the emergence of TYLCV in North America. These results further support the notion that geminiviruses evolve as rapidly as many RNA viruses.

scholarly journals First Report of East African Cassava Mosaic Begomovirus in Ghana

Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 877-877 ◽  
Author(s):  
S. K. Offei ◽  
M. Owuna-Kwakye ◽  
G. Thottappilly
Keyword(s):  
Monoclonal Antibodies ◽  
Rift Valley ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Enzyme Linked Immunosorbent Assay ◽  
International Institute ◽  
Virus Species ◽  
Tropical Agriculture ◽  
East African ◽  
Cassava Mosaic Virus

Virus species causing cassava mosaic disease have been categorized into three classes based on their reaction with monoclonal antibodies (MAbs) and their distribution (2). These viruses have different, scarcely overlapping distribution: African cassava mosaic begomovirus (ACMV) occurs in Africa west of the Rift Valley and in South Africa; East African cassava mosaic (EACMV) occurs in Africa east of the Rift Valley and in Madagascar; and Indian cassava mosaic virus (ICMV) occurs in India and Sri Lanka (2). During 1998, surveys were conducted in farmers' fields in Ghana to assess the incidence and reaction of local cassava cultivars to cassava mosaic disease. Leaf samples from symptomatic plants were indexed by triple antibody sandwich-enzyme-linked immunosorbent assay with crude extracts and monoclonal antibodies obtained from the International Institute of Tropical Agriculture (IITA). Each sample was assayed with monoclonal antibody SCR 23, which detects ACMV and EACMV, SCR 33, which detects ACMV, and SCR 58, which detects ICMV. None of the samples reacted with SCR 58. Two of the samples collected from the western region of Ghana produced strong reactions with MAb SCR23 but did not react with ACMV-specific MAb SCR 33. This result was consistent in three separate experiments conducted on the samples, confirming that the virus was EACMV and not ACMV. The results extend the work by Ogbe et al. (1) and provide further evidence of the occurrence of EACMV in west Africa. References: (1) F. O. Ogbe et al. Plant Dis 83:398, 1999. (2) M. M. Swanson and B. D. Harrison. Trop. Sci. 34:15, 1994.

scholarly journals Areal patterns in the vowel systems of the Macro-Sudan Belt

2020 ◽  
Vol 24 (1) ◽  
pp. 113-179
Author(s):  
Nicholas Rolle ◽  
Florian Lionnet ◽  
Matthew Faytak
Keyword(s):  
Statistical Tests ◽  
Central Africa ◽  
West African ◽  
Sub Saharan Africa ◽  
East African ◽  
Language Varieties ◽  
Phonological Features ◽  
Vowel Systems ◽  
Sub Saharan ◽  
Heterogeneous Region

AbstractThis paper investigates the areal distribution of vowel systems in the Macro-Sudan Belt, an area encompassing most of the western and central parts of northern Sub-Saharan Africa. We report on a survey of 681 language varieties with entries coded for two phonological features: advanced tongue root (ATR) harmony and the presence of interior vowels (i.e. non-peripheral vowels [ɨ ɯ ɜ ə ʌ … ]). Our results show that the presence of ATR harmony in the Macro-Sudan Belt is limited to three geographically unconnected zones: an Atlantic zone, a West African zone, and an East African zone. Between the West and East African ATR Zones is a genetically heterogeneous region where ATR harmony is systematically absent: we term this the Central African ATR-deficient zone. Our results show that in this same Central African zone, phonemic and allophonic interior vowels are disproportionately prevalent. Based on this distribution, we highlight two issues. First, ATR and interiority have an antagonistic relationship and do not commonly co-occur within vowel systems; this finding is supported through statistical tests. Second, our survey supports the existence of the Macro-Sudan Belt, but the discontinuous distribution of ATR harmony and its systematic absence in Central Africa challenges the proposal that this area represents the ‘hotbed’ of the Macro-Sudan Belt.

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