scholarly journals Heterosis and Heterotic Grouping among Tropical Maize Germplasm

2021 ◽  
Author(s):  
Richard Olutayo Akinwale
Keyword(s):  
Development Program ◽  
Sub Saharan Africa ◽  
Tropical Maize ◽  
Maize Production ◽  
Maize Germplasm ◽  
Tropical Germplasm ◽  
Maize Genetic ◽  
Sub Saharan ◽  
Future Direction ◽  
Hybrid Development

Maize (Zea mays L.) is the most important staple cereal cultivated in sub-Saharan Africa but its productivity is considerable low due to several factors. Development and deployment of maize hybrids have been reported as one of the crucial options in achieving sustainable maize production in sub-Saharan Africa. Information on the heterotic response among available genetic materials in a breeding program is valuable before commencement of any hybrid development program. Unlike the temperate germplasm, maize tropical germplasm is characterized with wide genetic base and genetic complexities and thus, proper organization of the pools, populations, varieties and inbreds that can serve as parental materials for hybrid development through identification of a distinct heterotic groups and patterns among tropical germplasm becomes very essential. This paper reviewed past research efforts at characterizing heterotic response among tropical maize genetic materials with a view to point out merits and demerits in the methods used and future direction towards achieving sustainable hybrid cultivation and enhancing food security in the sub-region.

Effects of planting density and nitrogen fertilization level on grain yield and harvest index in seven modern tropical maize hybrids (Zea maysL.)

2015 ◽  
Vol 154 (4) ◽  
pp. 689-704 ◽  
Author(s):  
S. TRACHSEL ◽  
F. M. SAN VICENTE ◽  
E. A. SUAREZ ◽  
C. S. RODRIGUEZ ◽  
G. N. ATLIN
Keyword(s):  
Grain Yield ◽  
Harvest Index ◽  
Dry Weight ◽  
Sub Saharan Africa ◽  
Planting Density ◽  
Tropical Maize ◽  
Shoot Dry Weight ◽  
Tropical Germplasm ◽  
Sub Saharan ◽  
Fertilization Level

SUMMARYTo support tropical maize (Zea maysL.) breeding efforts, the current work aimed to assess harvest index (HI) in modern hybrids and determine the effect of different planting densities on grain yield and HI under well-fertilized (HN) and nitrogen (N) deficient conditions. Harvest index and grain yield of 34 hybrids on average reached 0·42 and 7·06 t/ha (five environments), indicating a large potential for improvement in HI relative to temperate hybrids. Ear weight (r= 0·88), HI (r= 0·78) and shoot dry weight (r= 0·68) were strongly associated with grain yield. In the second experiment, seven hybrids were evaluated at planting densities of 5, 7, 9 and 11 plants/m2under HN (six environments) and N deficient (LN) conditions (four environments) to assess the effect of planting density on grain yield and HI. Grain yield increased by 40·4 and 21·8% under HN and LN conditions when planting density was increased relative to the lowest planting density. Harvest index increased from 0·42 at 5 plants/m2to 0·45 at 11 plants/m2under HN conditions and decreased from 0·44 at 5 plants/m2to 0·42 at 9 plants/m2under LN conditions. Harvest index was maximized at planting densities of 8·33 plants/m2and 5·30 plants/m2under HN and LN conditions, respectively, while grain yield was maximized at 9·93 plants/m2and 7·89/m2. Optimal planting density maximizing both HI and grain yield were higher than planting densities currently used in tropical germplasm. It can be concluded that productivity in tropical maize could be increased both under intensive (+40·4%) and lower-input management (+21·8%) by increasing planting densities above those currently used in smallholder agriculture in Latin America and Sub-Saharan Africa, in environments targeted by the International Maize and Wheat Improvement Center.

CHAPTER 5: Maize Lethal Necrosis, An Emerging Threat to Maize Production and Food Security in Sub-Saharan Africa

2020 ◽  
pp. 81-100
Author(s):  
Joel Masanga ◽  
Steven Runo ◽  
Francis Mwatuni ◽  
Cyrus Mugambi Micheni ◽  
Paul Kuria ◽  
...  
Keyword(s):  
Food Security ◽  
Sub Saharan Africa ◽  
Maize Production ◽  
Sub Saharan

scholarly journals Validation of Consensus Quantitative Trait Loci Associated with Resistance to Multiple Foliar Pathogens of Maize

2009 ◽  
Vol 99 (5) ◽  
pp. 540-547 ◽  
Author(s):  
Godfrey Asea ◽  
Bindiganavile S. Vivek ◽  
George Bigirwa ◽  
Patrick E. Lipps ◽  
Richard C. Pratt
Keyword(s):  
Quantitative Trait Loci ◽  
Disease Severity ◽  
Quantitative Trait ◽  
Gray Leaf Spot ◽  
Sub Saharan Africa ◽  
Maize Production ◽  
Resistant Parent ◽  
Trait Loci ◽  
Sub Saharan ◽  
Corn Leaf Blight

Maize production in sub-Saharan Africa incurs serious losses to epiphytotics of foliar diseases. Quantitative trait loci conditioning partial resistance (rQTL) to infection by causal agents of gray leaf spot (GLS), northern corn leaf blight (NCLB), and maize streak have been reported. Our objectives were to identify simple-sequence repeat (SSR) molecular markers linked to consensus rQTL and one recently identified rQTL associated with GLS, and to determine their suitability as tools for selection of improved host resistance. We conducted evaluations of disease severity phenotypes in separate field nurseries, each containing 410 F2:3 families derived from a cross between maize inbred CML202 (NCLB and maize streak resistant) and VP31 (a GLS-resistant breeding line) that possess complimentary rQTL. F2:3 families were selected for resistance based on genotypic (SSR marker), phenotypic, or combined data and the selected F3:4 families were reevaluated. Phenotypic values associated with SSR markers for consensus rQTL in bins 4.08 for GLS, 5.04 for NCLB, and 1.04 for maize streak significantly reduced disease severity in both generations based on single-factor analysis of variance and marker-interval analysis. These results were consistent with the presence of homozygous resistant parent alleles, except in bin 8.06, where markers were contributed by the NCLB-susceptible parent. Only one marker associated with resistance could be confirmed in bins 2.09 (GLS) and 3.06 (NCLB), illustrating the need for more robust rQTL discovery, fine-mapping, and validation prior to undertaking marker-based selection.

Molecular Improvement of Tropical Maize for Drought Stress Tolerance in Sub-Saharan Africa

2009 ◽  
Vol 28 (1-2) ◽  
pp. 16-35 ◽  
Author(s):  
Sylvester Anami ◽  
Marc De Block ◽  
Jesse Machuka ◽  
Mieke Van Lijsebettens
Keyword(s):  
Drought Stress ◽  
Stress Tolerance ◽  
Sub Saharan Africa ◽  
Tropical Maize ◽  
Drought Stress Tolerance ◽  
Sub Saharan

scholarly journals Genomic Prediction of Tropical Maize Resistance to Fall Armyworm and Weevils: Genomic Selection Should Focus on Effective Training Set Determination

2020 ◽  
Author(s):  
Arfang Badji ◽  
Lewis Machida ◽  
Daniel Bomet Kwemoi ◽  
Frank Kumi ◽  
Dennis Okii ◽  
...  
Keyword(s):  
Genomic Selection ◽  
Genomic Prediction ◽  
Insect Pests ◽  
Fall Armyworm ◽  
Sub Saharan Africa ◽  
Tropical Maize ◽  
Training Set ◽  
Maize Weevil ◽  
Maize Resistance ◽  
Sub Saharan

Genomic selection (GS) can accelerate variety release by shortening variety development phase when factors that influence prediction accuracies (PA) of genomic prediction (GP) models such as training set (TS) size and relationship with the breeding set (BS) are optimized beforehand. In this study, PAs for the resistance to fall armyworm (FAW) and maize weevil (MW) in a diverse tropical maize panel composed of 341 double haploid and inbred lines were estimated. Both phenotypic best linear unbiased predictors (BLUPs) and estimators (BLUEs) were predicted using 17 parametric, semi-parametric, and nonparametric algorithms with a 10-fold and 5 repetitions cross-validation strategy. n. For both MW and FAW resistance datasets with an RBTS of 37%, PAs achieved with BLUPs were at least as twice as higher than those realized with BLUEs. The PAs achieved with BLUPs for MW resistance traits: grain weight loss (GWL), adult progeny emergence (AP), and number of affected kernels (AK) varied from 0.66 to 0.82. The PAs were also high for FAW resistance RBTS datasets, varying from 0.694 to 0.714 (for RBTS of 37%) to 0.843 to 0.844 (for RBTS of 85%). The PAs for FAW resistance with PBTS were generally high varying from 0.83 to 0.86, except for one dataset that had PAs ranging from 0.11 to 0.75. GP models showed generally similar predictive abilities for each trait while the TS designation was determinant. There was a highly positive correlation (R=0.92***) between TS size and PAs for the RBTS approach while, for the PBTS, these parameters were highly negatively correlated (R=-0.44***), indicating the importance of the degree of kinship between the TS and the BS with the smallest TS (31%) achieving the highest PAs (0.86). This study paves the way towards the use of GS for maize resistance to insect pests in sub-Saharan Africa.

Contemporary and future direction of chromium tanning and management in sub Saharan Africa tanneries

2020 ◽  
Vol 133 ◽  
pp. 369-386 ◽  
Author(s):  
R.O. Oruko ◽  
R. Selvarajan ◽  
H.J.O. Ogola ◽  
J.N. Edokpayi ◽  
J.O. Odiyo
Keyword(s):  
Sub Saharan Africa ◽  
Sub Saharan ◽  
Future Direction

Maize systems under climate change in sub-Saharan Africa

2015 ◽  
Vol 7 (3) ◽  
pp. 247-271 ◽  
Author(s):  
Kindie Tesfaye ◽  
Sika Gbegbelegbe ◽  
Jill E Cairns ◽  
Bekele Shiferaw ◽  
Boddupalli M Prasanna ◽  
...  
Keyword(s):  
Climate Change ◽  
Sub Saharan Africa ◽  
Socioeconomic Impacts ◽  
Maize Production ◽  
Content Type ◽  
Maize Varieties ◽  
Sub Saharan ◽  
The Impact ◽  
Impacts Of Climate Change ◽  
Bioeconomic Models

Purpose – The purpose of this study is to examine the biophysical and socioeconomic impacts of climate change on maize production and food security in sub-Saharan Africa (SSA) using adapted improved maize varieties and well-calibrated and validated bioeconomic models. Design/methodology/approach – Using the past climate (1950-2000) as a baseline, the study estimated the biophysical impacts of climate change in 2050 (2040-2069) and 2080 (2070-2099) under the A1B emission scenario and three nitrogen levels, and the socioeconomic impacts in 2050. Findings – Climate change will affect maize yields across SSA in 2050 and 2080, and the extent of the impact at a given period will vary considerably between input levels, regions and maize mega environments (MMEs). Greater relative yield reductions may occur under medium and high-input intensification than under low intensification, in Western and Southern Africa than in Eastern and Central Africa and in lowland and dry mid-altitude than in highland and wet mid-altitude MMEs. Climate change may worsen food insecurity in SSA in 2050 through its negative impact on maize consumption and reduction in daily calorie intake. However, international trade has the potential to offset some of the negative impacts. Originality/value – The study calibrated and applied bioeconomic models to estimate the biophysical and socioeconomic impact of climate change on maize production at fine resolution. The results could be used as a baseline to evaluate measures that will be applied to adapt maize to the future climate in SSA.

Neurosurgery Education and Development program to treat hydrocephalus and to develop neurosurgery in Africa using mobile neuroendoscopic training

2015 ◽  
Vol 15 (6) ◽  
pp. 552-559 ◽  
Author(s):  
José Piquer ◽  
Mubashir Mahmood Qureshi ◽  
Paul H. Young ◽  
Robert J. Dempsey
Keyword(s):  
International Education ◽  
Development Program ◽  
Aqueductal Stenosis ◽  
Sub Saharan Africa ◽  
Third Ventriculostomy ◽  
Success Rates ◽  
Sub Saharan ◽  
Education And Development ◽  
Neurological Surgery

OBJECT A shortage of neurosurgeons and a lack of knowledge of neuroendoscopic management of hydrocephalus limits modern care in sub-Saharan Africa. Hence, a mobile teaching project for endoscopic third ventriculostomy (ETV) procedures and a subsequent program to develop neurosurgery as a permanent specialty in Kenya and Zanzibar were created and sponsored by the Neurosurgery Education and Development (NED) Foundation and the Foundation for International Education in Neurological Surgery. The objective of this work was to evaluate the results of surgical training and medical care in both projects from 2006 to 2013. METHODS Two portable neuroendoscopy systems were purchased and a total of 38 ETV workshops were organized in 21 hospitals in 7 different countries. Additionally, 49 medical expeditions were dispatched to the Coast General Hospital in Mombasa, Kenya, and to the Mnazi Moja Hospital in Zanzibar. RESULTS From the first project, a total of 376 infants with hydrocephalus received surgery. Six-month follow-up was achieved in 22%. In those who received follow-up, ETV efficacy was 51%. The best success rates were achieved with patients 1 year of age or older with aqueductal stenosis (73%). The main causes of hydrocephalus were infection (56%) and spina bifida (23%). The mobile education program interacted with 72 local surgeons and 122 nurses who were trained in ETV procedures. The second project involved 49 volunteer neurosurgeons who performed a total of 360 nonhydrocephalus neurosurgical operations since 2009. Furthermore, an agreement with the local government was signed to create the Mnazi Mmoja NED Institute in Zanzibar. CONCLUSIONS Mobile endoscopic treatment of hydrocephalus in East Africa results in reasonable success rates and has also led to major developments in medicine, particularly in the development of neurosurgery specialty care sites.

scholarly journals Genome-wide Association for Plant Height and Flowering Time across 15 Tropical Maize Populations under Managed Drought Stress and Well-Watered Conditions in Sub-Saharan Africa

Crop Science ◽  
2016 ◽  
Vol 56 (5) ◽  
pp. 2365-2378 ◽  
Author(s):  
Jason G. Wallace ◽  
Xuecai Zhang ◽  
Yoseph Beyene ◽  
Kassa Semagn ◽  
Michael Olsen ◽  
...  
Keyword(s):  
Drought Stress ◽  
Flowering Time ◽  
Plant Height ◽  
Sub Saharan Africa ◽  
Genome Wide Association ◽  
Tropical Maize ◽  
Maize Populations ◽  
Genome Wide ◽  
Sub Saharan
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