scholarly journals Historical Introgressions from a Wild Relative of Modern Cassava Improved Important Traits and May Be Under Balancing Selection

Genetics ◽  
2019 ◽  
Vol 213 (4) ◽  
pp. 1237-1253 ◽  
Author(s):  
Marnin D. Wolfe ◽  
Guillaume J. Bauchet ◽  
Ariel W. Chan ◽  
Roberto Lozano ◽  
Punna Ramu ◽  
...  
Keyword(s):  
Balancing Selection ◽  
Genetic Load ◽  
Sub Saharan Africa ◽  
Sub Saharan ◽  
Manihot Glaziovii ◽  
Disease Epidemics ◽  
Targeted Recombination ◽  
The Tropics ◽  
Modern Breeding ◽  
Elite Germplasm

Introgression of alleles from wild relatives has often been adaptive in plant breeding. However, the significance of historical hybridization events in modern breeding is often not clear. Cassava (Manihot esculenta) is among the most important staple foods in the world, sustaining hundreds of millions of people in the tropics, especially in sub-Saharan Africa. Widespread genotyping makes cassava a model for clonally propagated root and tuber crops in the developing world, and provides an opportunity to study the modern benefits and consequences of historical introgression. We detected large introgressed Manihot glaziovii genome-segments in a collection of 2742 modern cassava landraces and elite germplasm, the legacy of a 1930s era breeding to combat disease epidemics. African landraces and improved varieties were, on average, 3.8% (max 13.6%) introgressed. Introgressions accounted for a significant (mean 20%, max 56%) portion of the heritability of tested traits. M. glaziovii alleles on the distal 10 Mb of chr. 1 increased dry matter and root number. On chr. 4, introgressions in a 20 Mb region improved harvest index and brown streak disease tolerance. We observed the introgression frequency on chr. 1 double over three cycles of selection, and that later stage trials selectively excluded homozygotes from consideration as varieties. This indicates a heterozygous advantage of introgressions. However, we also found that maintaining large recombination-suppressed introgressions in the heterozygous state allowed the accumulation of deleterious mutations. We conclude that targeted recombination of introgressions would increase the efficiency of cassava breeding by allowing simultaneous fixation of beneficial alleles and purging of genetic load.

scholarly journals Introgressed Manihot glaziovii Alleles in Modern Cassava Germplasm Benefit Important Traits and Are Under Balancing Selection

2019 ◽  
Author(s):  
Marnin D. Wolfe ◽  
Guillaume J. Bauchet ◽  
Ariel W. Chan ◽  
Roberto Lozano ◽  
Punna Ramu ◽  
...  
Keyword(s):  
Manihot Esculenta ◽  
Developing World ◽  
Balancing Selection ◽  
Early Stage ◽  
Genetic Load ◽  
Mosaic Disease ◽  
Wild Relatives ◽  
Sub Saharan Africa ◽  
Sub Saharan ◽  
Manihot Glaziovii

1.AbstractIntrogression of alleles from wild relatives has often been adaptive, usually for disease resistance, in plant breeding. However, the significance of historical hybridization events in modern breeding is often not clear. Cassava (Manihot esculenta) is among the most important staple foods in the world, sustaining hundreds of millions of people in the tropics, especially in sub-Saharan Africa. Widespread genotyping makes cassava a model for clonally-propagated root and tuber crops in the developing world and provides an opportunity to study the modern benefits and consequences of historical introgression. We detected large introgressed M. glaziovii genome-segments in a collection of 2742 modern cassava landraces and elite germplasm, the legacy of 1930’s era breeding to combat epidemics disease. African landraces and improved varieties were on average 3.8% (max 13.6%) introgressed. Introgressions accounted for significant (mean 20%, max 56%) portion of the heritability of tested traits M. glaziovii alleles on the distal 10Mb of chr. 1 increased dry matter and root number. On chr. 4, introgressed alleles in a 20Mb region improved harvest index and brown streak disease tolerance. Three cycles of selection initially doubled the introgression frequency on chr. 1. Later stage variety trials selectively excluded homozygotes which indicates a heterozygous advantage. We show that maintaining large recombination-suppressed introgressions in the heterozygous state allows the accumulation of deleterious mutations. We conclude that targeted recombination of introgression segments would therefore increase the efficiency of cassava breeding by allowing simultaneous fixation of beneficial alleles and purging of genetic load.Significance StatementCrosses to wild relatives have often been adaptive for crop breeding, but their modern importance is usually poorly understood. Cassava (Manihot esculenta) is an important staple crop, feeding hundreds of millions in the developing world, and is a model for vegetatively-propagated non-inbred crops. In the 1930’s, crossing to M. glaziovii averted mosaic disease epidemic in Africa. We reveal that large genome segments, the legacy of those crosses, benefit a number of traits including yield in modern cassava and are consistently favored during selection. Elite cultivars are almost exclusively heterozygous for wild alleles; homozygotes are rejected during early stage trials, suggesting inbreeding depression. More recombination around beneficial wild alleles will allow purging of genetic load and increase genetic gain in cassava.

Susceptibility Profile of Aedes aegypti L. (Diptera: Culicidae) from Montclair, California, to Commonly Used Pesticides, With Note on Resistance to Pyriproxyfen

2019 ◽  
Vol 56 (4) ◽  
pp. 1047-1054 ◽  
Author(s):  
Tianyun Su ◽  
Jennifer Thieme ◽  
Taylor Lura ◽  
Min-Lee Cheng ◽  
Michelle Q Brown
Keyword(s):  
Aedes Aegypti ◽  
The United States ◽  
Urban Environments ◽  
Sub Saharan Africa ◽  
Modes Of Action ◽  
Breeding Populations ◽  
Laboratory Colony ◽  
Sub Saharan ◽  
The Tropics ◽  
And Control

Abstract The peridomestic anthropophilic Aedes aegypti L. (Diptera: Culicidae) is originated from the wild zoophilic subspecies Aedes aegypti formosus in sub-Saharan Africa, and currently has a broad distribution in human-modified environments of the tropics and subtropics worldwide. In California, breeding populations were initially detected in 2013 in the cities of Fresno, Madera, and San Mateo, and now can be found in 188 cities of 12 counties in the state. Recent genetic studies suggest that this species invaded California on multiple occasions from several regions of the United States and northern Mexico prior to initial detection. As an invasive species and vector for numerous arboviruses, Ae. aegypti is a primary target of surveillance and control in California. In southern California city of Montclair, a population was identified in September 2015, from which a short-term colony was established in an insectary. The susceptibility of this field population to commonly used pesticides with various modes of action, including 15 formulations against larvae and four against adults, was determined, in reference to a susceptible laboratory colony of the same species. No resistance was shown to most pesticides tested. However, tolerance or reduced susceptibility to spinosad, spinetoram, diflubezuron, and fipronil was detected, and modest levels of resistance to pyriproxyfen (resistance ratio = 38.7-fold at IE50 and 81.5-fold at IE90) was observed. Results are discussed based on the field usage and modes of action of the pesticides tested. Strategic selection and application of pesticides against this population of Ae. aegypti in the urban environments should be taken into consideration.

scholarly journals Twenty Years of Integrated Disease Surveillance and Response in Sub-Saharan Africa: Challenges and Opportunities for Effective Management of Infectious Disease Epidemics

2020 ◽  
Author(s):  
Irene Mremi ◽  
Janeth George ◽  
Susan F. Rumisha ◽  
Calvin Sindato ◽  
Leonard E.G. Mboera ◽  
...  
Keyword(s):  
Public Health ◽  
Infectious Disease ◽  
Health Information ◽  
Disease Surveillance ◽  
Sub Saharan Africa ◽  
Health Management Information System ◽  
Support Functions ◽  
Surveillance And Response ◽  
Sub Saharan ◽  
Disease Epidemics

Abstract Background: Public health surveillance requires valid, timely and complete health information for early detection of outbreaks. Countries in Sub-Saharan Africa (SSA) adopted Integrated Disease Surveillance and Response (IDSR) strategy in 1998 in response to an increased frequency of emerging and re-emerging diseases in the region. This systematic review aimed to analyse how IDSR implementation has embraced advancement in information technology, big data analytics techniques and wealth of data sources to strengthen detection and management of infectious disease epidemics in SSA. Methods: A search for eligible articles was done through HINARI, PubMed, and advanced Google Scholar databases. The review followed Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols checklist. Using the key search descriptors, 1,809 articles were identified and screened at two stages and 45 studies met the inclusion criteria for detailed review.Results: Of the 45 studies, 35 were country-specific, seven studies covered the region and three studies covered 3-4 countries. A total of 24 studies assessed the IDSR core functions while 42 studies assessed the support functions. Twenty-three studies addressed both the core and support functions. Most of the studies involved Tanzania (9), Ghana (6) and Uganda (5). The implementation of the IDSR strategy has shown improvements mainly in the support functions. The Health Management Information System (HMIS) has remained the main source of IDSR data. However, the HMIS system is characterised by inadequate data completeness, timeliness, quality, analysis and utilisation as well as lack of integration of data from sources other than health care facilities. Conclusion: In most SSA, HMIS is the main source of IDSR data, characterised by incompleteness, inconsistency and inaccuracy. This data is considered to be biased and reflects only the population seeking care from healthcare facilities. Community-based event-based surveillance is weak and non-existence in the majority of the countries. Data from other systems are not effectively utilized and integrated for surveillance. It is recommended that SSA countries consider and adopt multi-sectoral, multi-disease and multi-indicator platforms that integrate the existing surveillance systems with other sources of health information to provide support to effective detection and prompt response to public health threats.

scholarly journals 1.5°C Hotspots: Climate Hazards, Vulnerabilities, and Impacts

2018 ◽  
Vol 43 (1) ◽  
pp. 135-163 ◽  
Author(s):  
Carl-Friedrich Schleussner ◽  
Delphine Deryng ◽  
Sarah D'haen ◽  
William Hare ◽  
Tabea Lissner ◽  
...  
Keyword(s):  
Climate Change ◽  
Scientific Evidence ◽  
Climatic Conditions ◽  
Climate Impacts ◽  
Sub Saharan Africa ◽  
Global Mean Temperature ◽  
Climate Hazards ◽  
The Difference ◽  
Sub Saharan ◽  
The Tropics

Differentiating the impacts of climate change between 1.5°C and 2°C requires a regional and sector-specific perspective. Whereas for some regions and sectors the difference in climate variables might be indistinguishable from natural variability, other areas especially in the tropics and subtropics will experience significant shifts. In addition to region-specific changes in climatic conditions, vulnerability and exposure also differ substantially across the world. Even small differences in climate hazards can translate into sizeable impact differences for particularly vulnerable regions or sectors. Here, we review scientific evidence of regional differences in climate hazards at 1.5°C and 2°C and provide an assessment of selected hotspots of climate change, including small islands as well as rural, urban, and coastal areas in sub-Saharan Africa and South Asia, that are particularly affected by the additional 0.5°C global mean temperature increase. We interlink these with a review of the vulnerability and exposure literature related to these hotspots to provide an integrated perspective on the differences in climate impacts between 1.5°C and 2°C.

scholarly journals Solar geoengineering could redistribute malaria risk in developing countries

2020 ◽  
Author(s):  
Colin J. Carlson ◽  
Rita Colwell ◽  
Mohammad Sharif Hossain ◽  
Mohammed Mofizur Rahman ◽  
Alan Robock ◽  
...  
Keyword(s):  
At Risk ◽  
High Elevation ◽  
Malaria Risk ◽  
Sub Saharan Africa ◽  
Eastern Africa ◽  
Trade Offs ◽  
Populations At Risk ◽  
Solar Geoengineering ◽  
Sub Saharan ◽  
The Tropics

AbstractSolar geoengineering is often framed as a stopgap measure to decrease the magnitude, impacts, and injustice of climate change. However, the costs or benefits of geoengineering for human health are largely unknown. We project how geoengineering could impact malaria risk by comparing transmission suitability and populations-at-risk today against moderate and high emissions scenarios (RCP 4.5 and 8.5) with and without geoengineering over the next half-century. We show that if geoengineering deployment cools the tropics, it could help protect high elevation populations in eastern Africa from the encroachment of malaria, but could increase transmission in lowland sub-Saharan Africa and southern Asia. Compared to extreme warming, we also find that by 2070, geoengineering would nullify a projected reduction of nearly one billion people at risk of malaria. Our results indicate that geoengineering strategies designed to offset warming are not guaranteed to unilaterally improve health outcomes, and could produce regional trade-offs among Global South countries that are often excluded from geoengineering conversations.

scholarly journals Genomic balancing selection is key to the invasive success of the fall armyworm

2020 ◽  
Author(s):  
Sudeeptha Yainna ◽  
Wee Tek Tay ◽  
Estelle Fiteni ◽  
Fabrice Legeai ◽  
Anne-Laure Clamens ◽  
...  
Keyword(s):  
West Africa ◽  
Population Genomics ◽  
Balancing Selection ◽  
Fall Armyworm ◽  
Western Hemisphere ◽  
Sub Saharan Africa ◽  
Old World ◽  
Native Populations ◽  
Mild Reduction ◽  
Sub Saharan

AbstractA successful biological invasion involves survival in a newly occupied environment. If a population bottleneck occurs during an invasion, the resulting depletion of genetic variants could cause increased inbreeding depression and decreased adaptive potential, which may result in a fitness reduction. How invasive populations survive in the newly occupied environment despite reduced heterozygosity and how, in many cases, they maintain moderate levels of heterozygosity are still contentious issues1. The Fall armyworm (FAW; Lepidoptera: Spodoptera frugiperda), a polyphagous pest, is native to the Western hemisphere. Its invasion in the Old World was first reported from West Africa in early 2016, and in less than four years, it swept sub-Saharan Africa and Asia, finally reaching Australia. We used population genomics approaches to investigate the factors that may explain the invasive success of the FAW. Here we show that genomic balancing selection played a key role in invasive success by restoring heterozygosity before the global invasion. We observe a drastic loss of mitochondrial polymorphism in invasive populations, whereas nuclear heterozygosity exhibits a mild reduction. The population from Benin in West Africa has the lowest length of linkage disequilibrium amongst all invasive and native populations despite its reduced population size. This result indicates that balancing selection increased heterozygosity by facilitating the admixture of invasive populations from distinct origins and that, once heterozygosity was sufficiently high, FAW started spreading globally in the Old World. As comparable heterozygosity levels between invasive and native populations are commonly observed1, we postulate that the restoration of heterozygosity through balancing selection could be widespread among successful cases of biological invasions.

Replantation of amputation at the wrist: challenges of management in sub-Saharan Africa

2021 ◽  
Vol 14 (3) ◽  
pp. e238393
Author(s):  
Chidiebere Peter Echieh ◽  
Mba Ozinko ◽  
Benjamin Irene Omoregbee ◽  
Kelechi Emmanuel Okonta
Keyword(s):  
Social Interactions ◽  
Daily Life ◽  
Sub Saharan Africa ◽  
Loss Of Function ◽  
Left Wrist ◽  
Hand Surgeon ◽  
Sub Saharan ◽  
Daunting Challenge ◽  
The Tropics ◽  
Environmental Temperatures

Amputations of the upper limb, in particular, have a major impact on patients’ lives, as loss of function can not only cause reduced autonomy in daily life but also hinder social interactions and capacity for work. Replantation at or proximal to the wrist, referred to as wrist-proximal replantation, remains a daunting challenge that presents the hand surgeon with an array of difficulties distinct from digital replantation.We present our experience with a successful replantation of a near-complete amputation at the non-dominant left wrist in a 25-year-old man managed in sub-Saharan Africa. Two years after replantation, the patient had a Disabilities of the Arm, Shoulder and Hand score of 40 and 2-point discrimination of 6 mm. We also discuss the peculiar challenges which have limited the development of replantation in the tropics. Environmental temperatures, manpower, expertise and technology are possible factors that limit this practice in the tropics.

Role of Local Knowledge in Mixed Livestock Production Systems

2007 ◽  
Vol 36 (3) ◽  
pp. 187-192 ◽  
Author(s):  
Daniel M. Komwihangilo ◽  
Faustin P. Lekule ◽  
George C. Kajembe ◽  
Poul H. Petersen
Keyword(s):  
Local Knowledge ◽  
Production Systems ◽  
Smallholder Farmers ◽  
Livestock Production ◽  
Sub Saharan Africa ◽  
Livestock Feeds ◽  
Sub Saharan ◽  
The Tropics ◽  
Crop And Livestock Production

Local knowledge is an important asset for smallholder farmers who operate differently in diverse crop and livestock production systems in the tropics. Various methods are needed for its acquisition, analysis, storage and communication. While local knowledge of livestock feeds and other resources is abundant, amalgamation of the positive aspects of this knowledge system with that emanating from contemporary scientific approaches is critical yet limited. The merger is desirable so as to achieve improved productivity and sustainability of mixed livestock production systems in Sub-Saharan Africa.

scholarly journals Clinical Spectrum of Schistosomiasis: An Update

2021 ◽  
Vol 10 (23) ◽  
pp. 5521
Author(s):  
Cristina Carbonell ◽  
Beatriz Rodríguez-Alonso ◽  
Amparo López-Bernús ◽  
Hugo Almeida ◽  
Inmaculada Galindo-Pérez ◽  
...  
Keyword(s):  
Neglected Tropical Diseases ◽  
Clinical Manifestations ◽  
Public Health Problem ◽  
Sub Saharan Africa ◽  
Clinical Form ◽  
Important Public Health Problem ◽  
Blood Flukes ◽  
Helminthic Infection ◽  
Sub Saharan ◽  
The Tropics

Schistosomiasis is a helminthic infection and one of the neglected tropical diseases (NTDs). It is caused by blood flukes of the genus Schistosoma. It is an important public health problem, particularly in poverty-stricken areas, especially those within the tropics and subtropics. It is estimated that at least 236 million people worldwide are infected, 90% of them in sub-Saharan Africa, and that this disease causes approximately 300,000 deaths annually. The clinical manifestations are varied and affect practically all organs. There are substantial differences in the clinical presentation, depending on the phase and clinical form of schistosomiasis in which it occurs. Schistosomiasis can remain undiagnosed for a long period of time, with secondary clinical lesion. Here, we review the clinical profile of schistosomiasis. This information may aid in the development of more efficacious treatments and improved disease prognosis.

scholarly journals Sources of Resistance for Two-spotted Spider Mite (Tetranychus urticae) in Scarlet (Solanum aethiopicum L.) and Gboma (S. macrocarpon L.) Eggplant Germplasms

HortScience ◽  
2019 ◽  
Vol 54 (2) ◽  
pp. 240-245 ◽  
Author(s):  
Dalia Taher ◽  
Mohamed Rakha ◽  
Srinivasan Ramasamy ◽  
Svein Solberg ◽  
Roland Schafleitner
Keyword(s):  
Tetranychus Urticae ◽  
Spider Mite ◽  
Glandular Trichome ◽  
Sub Saharan Africa ◽  
Leaf Damage ◽  
Sources Of Resistance ◽  
Solanum Aethiopicum ◽  
Sub Saharan ◽  
Two Spotted Spider Mite ◽  
The Tropics

The two-spotted spider mite, Tetranychus urticae, is a serious global pest of eggplants and other vegetables in the tropics and subtropics. The scarlet (Solanum aethiopicum L.) and gboma (Solanum macrocarpon L.) are two cultivated eggplants indigenous to sub-Saharan Africa. In this study, 120 accessions of S. aethiopicum and five accessions of S. macrocarpon from the World Vegetable Center’s genebank collection were evaluated for spider mite resistance based on leaf damage scores and trichome types and densities. The highest levels of resistance were detected in S. macrocarpon accessions VI050393 and VI050444. In addition, two accessions of S. aethiopicum, VI042749 and VI042753, were moderately resistant. All other S. aethiopicum accessions were susceptible or highly susceptible. Spider mite resistance was significantly associated with the presence of type VII glandular trichome, but nonglandular stellate trichomes were not associated with resistance. The resistant S. macrocarpon accessions can be directly used as resistant cultivars or in prebreeding programs aimed at breeding resistant lines of the most commonly cultivated eggplant (S. melogena).

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