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Resources

Read on key developments in maize research and seed production in Africa.
Title
The latest STMA Bulletin is out
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The latest from the Stress Tolerant Maize for Africa (STMA) initiative. This issue talks about product profiling, costing of maize breeding, highlights of CIMMYT's Kenya Annual Partner Days and portraits of Kenyan farmers who have adopted stress-tolerant maize varieties. Read STMA Bulletin - 17-10-2019vf   Download
STMA Bulletin April-June 2019
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Some of the latest research breakthrough and impact from the Stress Tolerant Maize for Africa initiative. Download
STMA Bulletin Jan-March 2019
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Maize ear imaging tool for faster breeding selection, testimonies of farmers adopting drought-tolerant maize varieties in Kenya, how to do gender sensitive variety promotion and research on the seed value chain.  Find out about the latest developments of the Stress Tolerant Maize for Africa initiative. Download
STMA January – March 2017 Issue 1
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Access to affordable improved maize varieties by part of the 200 million African smallholders who relentlessly grow and depend on maize for food and livelihood is a key focus for CIMMYT and the International Institute of Tropical Agriculture (IITA). Together with partners they are working to boost Africa’s maize farming and seed systems through the Stress Tolerant Maize for Africa (STMA) project. Download
DT Maize Vol.4 no.3
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The last edition of DTMaize bulletin in 2015 focuses on maize production in Kenya. Maize accounts for 40 percent of all crop area, and is Kenya’s most important crop, accounting for more than 51 percent of all staples grown in the country. Maize is produced for both home consumption and market – with small-scale farmers only selling an estimated 20 percent of their production. The bulletin also highlights the end of Africa’s two key maize projects – the Drought Tolerant Maize for Africa and Improved Maize for African Soils – that wind up after 8 and 5 years (respectively) of maize work in sub-Saharan Africa. Download
DT Maize Vol. 2 No. 1 March 2013
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT MAIZE. A quarterly Bulletin of the Drought Tolerant Maize for Africa Project
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub-Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT Maize Vol. 2 No. 4 December 2013
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT Maize Vol. 2 No. 3 September 2013
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT Maize Vol. 2 No. 2 June 2013
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT Maize Bulletin: Vol 3. No. 4 December 2014
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DTMA Moves to the Next Level: Welcoming DTMASS The December issue of the DT Maize Bulletin celebrates the launch of a new project, Drought Tolerant Maize for Africa Seed Scaling (DTMASS), was born out of the progress made by DTMA and other CIMMYT-Africa maize projects between 2007 and 2014. Over 80 stakeholder representatives gathered for the official project launch on 17-18 November 2014 in Addis Ababa. Funded by the United States Agency for International Development (USAID), the project is implemented in seven countries in eastern (Ethiopia, Kenya, Tanzania, and Uganda) and southern (Malawi, Mozambique, and Zambia) Africa Download
DT Maize Bulletin: Vol 3. No. 2. June 2014
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Angola Fast-Tracks New Drought-Tolerant Maize Varieties Angola is a country of immense mineral wealth andenjoys huge agricultural potential because of its vast land and water resources. It produces a number of staples; a 2013 DTMA household survey shows maize occupies about 63 percent of all the crops grown in Angola. Download
DTMA Project Platform. January – June 2009
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This newsletter summarizes key events in the DTMA region, from January to June 2009. Download
DTMA Project Platform. November 2007 – February 2008
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This newsletter gives an account of DTMA activities for a four-month period, from November 2007 to February 2008.

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DTMA Platform Jan-Apr 2010
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In this issue, we turn the spotlight on West Africa, and we also begin a new section – ‘Country Partner Updates’. Share your feedback and submissions for the next issue of the DTMA Platform, to be published in July. Happy reading! Download
DTMA Project Platform. October – December 2009
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In this newsletter, you will find updates on the DTMA program for the last trimester of 2009.! Download
DTMA Project Platform. July – September 2009
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This issue of the Platform covers events from July to September 2009. Download
DTMA Annual Highlights 2010
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Drought-tolerant maize for Africa: Better food security and livelihoods Download
DTMA Platform Aug-Nov2010
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In this issue we focus on the insights shared during the recent annual meeting, varieties released to date, and training initiatives. Download
DTMA Platform April-July 2010
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In this issue we turn the spotlight on our country partner, Malawi and also focus on training and seedrelated initiatives and news. Download
DT Maize Vol. 1 No. 2, September 2012
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
DT Maize Vol. 1 No. 1, June 2012
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is to inform partners and the general public at large about developments related to drought tolerant maize in Sub- Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated Download
DTMA Platform Dec 2011 – March 2012
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This issue of the DTMA Platform newsletter highlights events from December 2011 to March 2012.
These are:

DTMA and DFID win 2012 UK Climate Week Award
Bill Gates announces more funding for DTMA III at IFAD session
Empowering maize technicians in Zimbabwe
Kenya and Uganda DTMA excellence awards
DTMA III kicks off and gets new advisory board

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DTMA Project Platform. January – April 2011
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In this newsletter, you will find updates on the DTMA program for the last trimester of 2011. Download
DT Maize Vol. 1 No 3, December 2012
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DT Maize is a quarterly publication of the DTMA (Drought Tolerant Maize for Africa) project, funded by the Bill & Melinda Gates Foundation. Its aim is toinform partners and the general public at large about developments related to drought tolerant maize in Sub-Saharan Africa. It publishes short, general articles, relevant news, and events related to DTMA. Articles and news on all aspects of maize in Africa from sister projects and other partners are also welcome. Any feedback from our readers would be appreciated. Download
     

    STMA Fact Sheet

    Learn more about STMA work and partnership across the 12 target countries in Africa

    Download Fact Sheet

    Handbook

    Title
    Food safety and adverse selection in rural maize markets
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    Without enforced standards or reliable third‐party verification, food safety threats such as pesticide residues and aflatoxin contamination are generally unobservable or only partially observable to both buyers and sellers, especially of staple foods in rural maize markets in sub‐Saharan Africa. As a result, sellers have more information about food quality than do buyers. Such information asymmetries can impede market development and undermine human health. We study farm household behaviour in the context of imperfect food safety information. We pool observations obtained from 707 food storage containers maintained by 309 farm households in Benin, surveyed following the maize harvests of 2011/2012 and 2013/2014. Our results indicate that when a household perceives a food safety risk associated with application of insecticides, on average it is 33 percentage points less likely to apply insecticides to maize it intends to consume than it is to maize it intends to sell. These individuals are also more likely to sell maize than households without food safety concerns. Results highlight the potential value of improved storage technologies and quality control to promote market transactions and reduce hidden health risks. Download
    Genetic studies of extra-early provitamin-A maize inbred lines and their hybrids in multiple environments
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    Vitamin A deficiency, drought, low soil nitrogen (low N) and Striga hermonthica parasitism of maize (Zea mays L.) cause malnutrition and food insecurity in sub-Saharan Africa. The objectives of this study were to determine combining abilities of extra-early provitamin A (PVA) lines, classify them into heterotic groups (HGs), identify testers, and determine yield stability of hybrids under contrasting environments in two trials. In trial 1, 20 extra-early PVA lines were inter-mated in a diallel mating scheme to obtain 190 F1 hybrids. The 190 F1 hybrids plus six checks were tested under Striga infestation, drought, and stress-free environments in Nigeria from 2015 to 2017. In trial 2, 35 extra-early yellow hybrids were evaluated under low N, Striga-infested and stress-free environments in 2018. Provitamin A concentrations of 23.98  and 22.56 µg g-1 were obtained for TZEEIOR 202 and TZEEIOR 205. TZEEIOR 197 × TZEEIOR 205 (20.1 μg g-1) and TZEEIOR 202 × TZEEIOR 205 (22.7 μg g-1) contained about double the PVA level of the commercial check, TZEEI 58 × TZEE-Y Pop STR C5 (11.4 μg  g -1). Both general (GCA) and specific (SCA) combining ability variances were statistically significant for most agronomic traits, although GCA was much larger than SCA effects,  indicating that additive genetic effects primarily controlled the inheritance of those traits. TZEEIOR 97 and TZEEIOR 197 were identified as inbred testers. TZEEIOR 197 × TZEEIOR  205 (20.1 μg g-1) was identified as a single-cross tester as well as the most stable and highest yielding hybrid across environments. TZEEIOR 202 and TZEEIOR 205 should be invaluable  resources for breeding for high PVA. PVA level was independent of hybrid yield potential, indicating that selection of superior hybrids with elevated PVA levels should be feasible. Download
    Assessment of genetic diversity for drought, heat and combined drought and heat stress tolerance in early maturing maize landraces
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    Climate change is expected to aggravate the effects of drought, heat and combined drought and heat stresses. An important step in developing ‘climate smart’ maize varieties is to identify germplasmwithgoodlevelsoftolerancetotheabioticstresses. Theprimaryobjectiveofthisstudywas toidentifylandraceswithcombinedhighyieldpotentialanddesirablesecondarytraitsunderdrought, heat and combined drought and heat stresses. Thirty-three landraces from Burkina Faso (6), Ghana (6) and Togo (21), and three drought-tolerant populations/varieties from the Maize Improvement Program at the International Institute of Tropical Agriculture were evaluated under three conditions, namely managed drought stress, heat stress and combined drought and heat stress, with optimal growing conditions as control, for two years. The phenotypic and genetic correlations between grain yield of the different treatments were very weak, suggesting the presence of independent genetic control of yield to these stresses. However, grain yield under heat and combined drought and heat stresses were highly and positively correlated, indicating that heat-tolerant genotypes would most likely tolerate combined drought and stress. Yield reduction averaged 46% under managed drought stress, 55% under heat stress, and 66% under combined drought and heat stress, which reflected hypo-additive effect of drought and heat stress on grain yield of the maize accessions. Accession GH-3505 was highly tolerant to drought, while GH-4859 and TZm-1353 were tolerant to the three stresses. These landrace accessions can be invaluable sources of genes/alleles for breeding for adaptation of maize to climate change. Download
    Genetic analysis of grain yield and agronomic traits of early provitamin A quality protein maize inbred lines in contrasting environments
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    Early-maturing provitamin A (PVA) quality protein maize (QPM) hybrids with combined drought and low soil nitrogen (low-N) tolerance are needed to address malnutrition and food security problems in sub-Saharan Africa (SSA). The current study’s objectives were to (i) examine combining ability of selected early maturing PVA-QPM inbreds for grain yield and other agronomic traits under drought, low-N, optimal environments and across environments, (ii) determine gene action conditioning PVA accumulation under optimal environments, (iii) classify inbreds into heterotic groups and identify testers and (iv) assess yield and stability of hybrids across environments. Ninety-six hybrids generated from 24 inbred lines using the North Carolina Design II together with four commercial hybrid controls were evaluated under drought, low-N and optimal environments in Nigeria in 2016 and 2017. Fifty-four selected hybrids were assayed for PVA carotenoid and tryptophan content. Additive genetic effects were greater than non-additive effects for grain yield and most agronomic traits under each and across environments. The gene action conditioning accumulation of PVA carotenoids under optimal growing conditions followed a pattern similar to that of grain yield and other yield-related traits. The inbred lines were categorized into four heterotic groups consistent with the pedigree records and with TZEIORQ 29 identified as the best male and female tester for heterotic group IV. No tester was found for the other groups. Hybrid TZEIORQ 24 × TZEIORQ 41 was the highest yielding and most stable across environments and should be further tested for consistent performance for commercialization in SSA. Download
    Testcross performance and combining ability of early maturing maize inbreds under multiple-stress environments
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    Availability of multiple-stress tolerant maize is critical for improvement in maize production in West and central Africa (WcA). A study was carried out to (i) assess a set of inbred lines for combining ability under stressed and optimal conditions, (ii) determine the performance of the testcrosses under different conditions, and (iii) identify outstanding hybrids across the conditions. Two hundred and five testcrosses were planted with five hybrid checks under Striga-infested, low soil nitrogen, drought and optimal conditions between 2015 and 2016 in Nigeria. The grain yield inheritance under optimal condition was largely regulated by additive gene effect whereas non-additive gene effects largely regulated grain yield under the three stresses. Four of the inbreds had significant positive general combining ability effects each under low N and drought, and three under Striga infestation for grain yield. The inbreds could be vital sources of beneficial alleles for development and improvement of tropical yellow maize hybrids and populations. Hybrids TZEI 443 x ENT 13 and TZEI 462 x TZEI 10 were high yielding and stable; they out-performed the three early maturing released hybrids in WCA. The new hybrids should be extensively assessed and released in the sub-region to improve food security Download
    Inheritance of Striga hermonthica adaptive traits in an early-maturing white maize inbred line containing resistance genes from Zea diploperennis
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    Striga hermonthica can cause as high as 100% yield loss in maize depending on soil fertility level, type of genotype, severity of infestation and climatic conditions. Understanding the mode of inheritance of Striga resistance in maize is crucial for introgression of resistance genes into tropical germplasm and deployment of resistant varieties. This study examined the mode of inheritance of resistance to Striga in earlymaturing inbred line, TZdEI 352 containing resistance genes from Zea diploperennis. Six generations, P1, P2, F1, F2, BC1P1 and BC1P2 derived from a cross between resistant line, TZdEI 352 and susceptible line, TZdEI 425 were screened under artificial Striga infestation at Mokwa and Abuja, Nigeria, 2015. Additive‐dominance model was adequate in describing observed variations in the number of emerged Striga plants among the population; hence, digenic epistatic model was adopted for Striga damage. Dominance effects were higher than the additive effects for the number of emerged Striga plants at both locations signifying that non‐additive gene action conditioned inheritance of Striga resistance. Inbred TZdEI 352 could serve as invaluable parent for hybrid development in Striga endemic agro‐ecologies of sub‐Saharan Africa. Download
    Studies on estimation of heterosis for striga resistance in maize test crosses in Mali
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    Heterosis for yield, secondary traits and Striga resistance was estimated in maize test crosses generated from fifteen inbred lines and three testers using line by tester analysis. Hybrids, testcrosses and parents were evaluated for two years at Agricultural Research Institute, Sotuba and Sanankoroba, to identify combinations expressing high hybrid vigor in Mali under Striga- infested and Striga-free conditions. Under Striga-free condition TZISTR106 /TZISTR1230, TZISTR106/TZISTR1223 and TZISTR1033/ TZISTR1223 appeared as the best hybrids combinations with respect to grain yield, while combinations TZISTR1207/ TZISTR1226, TZISTR106 /TZISTR112, TZISTR106 / TZISTR113 and TZISTR106/ TZISTR1028 showed positive mid parent heterosis for grain yield and negative mid parent heterosis for Striga related traits under Striga infestation. These hybrids are worthy for further utilization. Keywords: Heterosis, lattice design, genotypes, Striga related traits, maize. Download
    Association studies between grain yield and agronomic traits of a MARS maize (Zea mays L.) population under drought and non-stress condition
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    The study aimed at examining the associations between yield and other traits under drought stress and non-stress conditions. A total of 150 MARS testcrosses were evaluated under both conditions at the International Institute of Tropical Agriculture substation for two years under during the dry season. Genotypic and phenotypic correlation, multiple stepwise regression and path co-efficient analyses were carried out to examine the relationship among the traits under both environments. Results showed anthesis-silking interval, days to silking, husk cover and plant aspect were significantly associated with yield under drought condition at both genotypic and phenotypic levels. Yield was positively correlated with plant and ear height but had a negative correlation with plant and ear aspect at both levels under well-watered condition. Regression analysis showed that ears per plant, plant aspect, ear aspect, days to silking, leaf death and plant height had a direct effect on yield, contributing a total of 71.1 % of observed variation under drought, while ears per plant, ear aspect, plant aspect, days to pollen shed, days to silking and plant height contributed about 31.42 % to yield under wellwatered conditions. The study concluded that these traits be used as selection criteria as it will aid improvement of maize yield. Key words: maize; association; grain yield; drought; well-watered; MARS; testcross Download
    Yield gains and associated changes in an early yellow bi-parental maize population following genomic selection for Striga resistance and drought tolerance
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    Background: Maize yield potential is rarely maximized in sub-Saharan Africa (SSA) due to the devastating effects of drought stress and Striga hermonthica parasitism. This study was conducted to determine the gains in grain yield and associated changes in an early-maturing yellow bi-parental maize population (TZEI 17 x TZEI 11) F3 following genomic selection (GS) for improved grain yield, Striga resistance and drought tolerance. Fifty S1 lines were extracted from each of cycles C0,C 1,C 2 and C3 of the population and crossed to a tester TZEI 23 to generate 200 testcrosses. The testcrosses were evaluated under drought, artificial Striga-infested and optimal (free from Striga infestation and without limitation of water and nitrogen) environments in Nigeria, 2014-2017. Results: Gains in grain yield of 498kgha− 1 cycle− 1 (16.9% cycle− 1) and 522kgha−1 cycle− 1 (12.6% cycle− 1) were obtained under Striga-infested and optimal environments, respectively. The yield gain under Striga-infested environments was associated with increased plant and ear heights as well as improvement in root lodging resistance, husk cover, ear aspect and Striga tolerance. Under optimal environments, yield gain was accompanied by increase in plant and ear heights along with improvement of husk cover and ear rot resistance. In contrast, genomic selection did not improve grain yield under drought but resulted in delayed flowering, poor pollen-silk synchrony during flowering and increased ear height. Genetic variances and heritabilities for most measured traits were not significant for the selection cycles under the research environments. Ear aspect was a major contributor to grain yield under all research environments and could serve as an indirect selection criterion for simultaneous improvement of grain yield under drought, Striga and optimal environments. Conclusion: This study demonstrated that genomic selection was effective for yield improvement in the bi-parental maize population under Striga-infested environments and resulted in concomitant yield gains under optimal environments. However, due to low genetic variability of most traits in the population, progress from further genomic selection could only be guaranteed if new sources of genes for Striga resistance and drought tolerance are introgressed into the population. Keywords: Genomic selection, Striga resistance, Drought tolerance, Maize, Testcrosses Download
    Genetic diversity and population structure of early-maturing tropical maize inbred lines using SNP markers
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    Information on genetic diversity and population structure are very important in any breeding programme for the improvement of traits of interest and the development of outstanding products for commercialization. In the present study, we assessed the genetic diversity of 94 early-maturing white and yellow tropical maize inbred lines using single nucleotide polymorphism (SNP) markers. The larger number of SNP markers used in this study allowed a clearer inference of the population structure of the 94 inbred lines. Cluster analysis resolved the inbred lines into different clusters based on their pedigree, selection history and endosperm colour. However, three heterotic groups were revealed by population structure analysis, but additional field evaluation could be more informative to confirm the heterotic groups identified. Nevertheless, wide genetic variability existed among the inbred lines making them unique with the potential to contribute new beneficial alleles to maize breeding programmes in the tropics, especially in the West and Central Africa (WCA) sub-region. Download
    An Integrated Molecular and Conventional Breeding Scheme for Enhancing Genetic Gain in Maize in Africa
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    Maize production in West and Central Africa (WCA) is constrained by a wide range of interacting stresses that keep productivity below potential yields. Among the many problems afflicting maize production in WCA, drought, foliar diseases, and parasitic weeds are the most critical. Several decades of efforts devoted to the genetic improvement of maize have resulted in remarkable genetic gain, leading to increased yields of maize on farmers’ fields. The revolution unfolding in the areas of genomics, bioinformatics, and phenomics is generating innovative tools, resources, and technologies for transforming crop breeding programs. It is envisaged that such tools will be integrated within maize breeding programs, thereby advancing these programs and addressing current and future challenges. Accordingly, the maize improvement program within International Institute of Tropical Agriculture (IITA) is undergoing a process of modernization through the introduction of innovative tools and new schemes that are expected to enhance genetic gains and impact on smallholder farmers in the region. Genomic tools enable genetic dissections of complex traits and promote an understanding of the physiological basis of key agronomic and nutritional quality traits. Marker-aided selection and genomewide selection schemes are being implemented to accelerate genetic gain relating to yield, resilience, and nutritional quality. Therefore, strategies that effectively combine genotypic information with data from field phenotyping and laboratory-based analysis are currently being optimized. Molecular breeding, guided by methodically defined product profiles tailored to different agroecological zones and conditions of climate change, supported by state-of-the-art decision-making tools, is pivotal for the advancement of modern, genomics-aided maize improvement programs. Accelerated genetic gain, in turn, catalyzes a faster variety replacement rate. It is critical to forge and strengthen partnerships for enhancing the impacts of breeding products on farmers’ livelihood. IITA has well-established channels for delivering its research products/technologies to partner organizations for further testing, multiplication, and dissemination across various countries within the subregion. Capacity building of national agricultural research system (NARS) will facilitate the smooth transfer of technologies and best practices from IITA and its partners. Download
    Genome-Wide Association Mapping and Genomic Prediction Analyses Reveal the Genetic Architecture of Grain Yield and Flowering Time Under Drought and Heat Stress Conditions in Maize
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    Drought stress (DS) is a major constraint to maize yield production. Heat stress (HS) alone and in combination with DS are likely to become the increasing constraints. Association mapping and genomic prediction (GP) analyses were conducted in a collection of 300 tropical and subtropical maize inbred lines to reveal the genetic architecture of grain yield and flowering time under well-watered (WW), DS, HS, and combined DS and HS conditions. Out of the 381,165 genotyping-by-sequencing SNPs, 1549 SNPs were significantly associated with all the 12 trait-environment combinations, the average PVE (phenotypic variation explained) by these SNPs was 4.33%, and 541 of them had a PVE value greater than 5%. These significant associations were clustered into 446 genomic regions with a window size of 20 Mb per region, and 673 candidate genes containing the significantly associated SNPs were identified. In addition, 33 hotspots were identified for 12 trait-environment combinations and most were located on chromosomes 1 and 8. Compared with single SNP-based association mapping, the haplotype-based associated mapping detected fewer number of significant associations and candidate genes with higher PVE values. All the 688 candidate genes were enriched into 15 gene ontology terms, and 46 candidate genes showed significant differential expression under the WW and DS conditions. Association mapping results identified few overlapped significant markers and candidate genes for the same traits evaluated under different managements, indicating the genetic divergence between the individual stress tolerance and the combined drought and HS tolerance. The GP accuracies obtained from the marker-trait associated SNPs were relatively higher than those obtained from the genome-wide SNPs for most of the target traits. The genetic architecture information of the grain yield and flowering time revealed in this study, and the genomic regions identified for the different trait-environment combinations are useful in accelerating the efforts on rapid development of the stress-tolerant maize germplasm through marker-assisted selection and/or genomic selection. Download
    Identification of donors for low-nitrogen stress with maize lethal necrosis (MLN) tolerance for maize breeding in sub- Saharan Africa
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    After drought, a major challenge to smallholder farmers in sub-Saharan Africa is low-fertility soils with poor nitrogen (N)-supplying capacity. Many challenges in this region need to be overcome to create a viable fertilizer market. An intermediate solution is the development of maize varieties with an enhanced ability to take up or utilize N in severely depleted soils, and to more efficiently use the small amounts of N that farmers can supply to their crops. Over 400 elite inbred lines from seven maize breeding programs were screened to identify new sources of tolerance to low-N stress and maize lethal necrosis (MLN) for introgression into Africa-adapted elite germplasm. Lines with high levels of tolerance to both stresses were identified. Lines previously considered to be tolerant to low-N stress ranked in the bottom 10% under low-N confirming the need to replace these lines with new donors identified in this study. The lines that performed best under low-N yielded about 0.5 Mg ha-1 (20%) more in testcross combinations than some widely used commercial parent lines such as CML442 and CML395. This is the first large scale study to identify maize inbred lines with tolerance to low-N stress and MLN in eastern and southern Africa. Download
    Performance and yield stability of maize hybrids in stress-prone environments in eastern Africa
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    Identification and deployment of high-yielding and stress-tolerant maize hybrids adapted to stress-prone agro-ecologies is important for improving the food security and livelihoods of smallholder farmers in eastern Africa. The objectives of this study were to (i) assess the performance of maize hybrids under well-watered and drought stress conditions; (ii) evaluate grain yield stability of 65 intermediate-maturing and 55 early-maturing hybrids in 24 well-watered locations and seven drought stress locations; and (iii) identify representative and/or discriminative testing locations for increasing genetic gains for the target traits. There were significant differences for grain yield among early- and intermediate maturing hybrids tested under well-watered and drought stress environments. Among the early-maturing hybrids, the top 10 hybrids produced 46.8%–73.9% and 31.2%–42.1% higher mean grain yields than the best commercial check under drought and well-watered conditions, respectively. Among the intermediate-maturing hybrids, the top 10 hybrids produced 25.2%–47.7% and 8.5%–13.5% higher grain yield than commercial checks under drought stress and well-watered conditions, respectively, suggesting improvement in the levels of drought tolerance in both early- and intermediate-maturing hybrids. GGE biplot analysis and a bi-segmented regression linear method identified specific early-maturing and intermediate-maturing hybrids that performed well under both well-watered and drought stress conditions. These hybrids could be recommended for commercial production in eastern Africa. Kakamega in Kenya was found to be the most representative and highly discriminating site among well-watered testing locations, while Kabuku in Tanzania was the least representative of test locations. For testing under drought stress conditions, Kiboko in Kenya was identified as the most representative location. This information could be useful for allocating resources and streamlining CIMMYT maize hybrid testing in eastern Africa. Download
    Molecular diversity and selective sweeps in maize inbred lines adapted to African highlands
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    Little is known on maize germplasm adapted to the African highland agro-ecologies. In this study, we analyzed high-density genotyping by sequencing (GBS) data of 298 African highland adapted maize inbred lines to (i) assess the extent of genetic purity, genetic relatedness, and population structure, and (ii) identify genomic regions that have undergone selection (selective sweeps) in response to adaptation to highland environments. Nearly 91% of the pairs of inbred lines differed by 30–36% of the scored alleles, but only 32% of the pairs of the inbred lines had relative kinship coefficient <0.050, which suggests the presence of substantial redundancy in allelic composition that may be due to repeated use of fewer genetic backgrounds (source germplasm) during line development. Results from different genetic relatedness and population structure analyses revealed three different groups, which generally agrees with pedigree information and breeding history, but less so by heterotic groups and endosperm modification. We identified 944 single nucleotide polymorphic (SNP) markers that fell within 22 selective sweeps that harbored 265 protein-coding candidate genes of which some of the candidate genes had known functions. Details of the candidate genes with known functions and differences in nucleotide diversity among groups predicted based on multivariate methods have been discussed. Download
    Weighting methods for variance heterogeneity in phenotypic and genomic data analysis for crop breeding
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    In plant breeding programmes multi-environment trials (MET) form the backbone for phenotypic selection, Genomic Selection (GS) and Genome Wide Association Study (GWAS)Efficient analysis of MET is fundamental to get accurate results from phenotypic selection, GS and GWAS. On the other hand inefficient analysis of MET data may have consequences such as biased ranking of genotype means in phenotypic data analysis, small accuracy of GS and wrong identification of QTL in GWAS analysis. A combined analysis of MET is performed using either single-stage or stage-wise (two-stage) approaches based on the linear mixed model framework. While single-stage analysis is a fully efficient approach, MET data is suitably analyzed using stage-wise methods. MET data often show within-trial and between-trial variance heterogeneities, which is in contradiction with the homogeneity of variance assumption of linear models, and these heterogeneities require corrections. In addition it is well documented that spatial correlations are inherent to most field trials. Appropriate remedial techniques for variance heterogeneities and proper accounting of spatial correlation are useful to improve accuracy and efficiency of MET analysis. The study conducted based on three maize trials from Ethiopia compares methods for simultaneous handling of within-trial variance heterogeneity and within-trial spatial correlation. To stabilize variance Box-Cox transformation was considered. The result shows that, while the Box-Cox transformation was suitable for stabilizing the variance, it is difficult to report results on the original scale. As alternative variance models, i.e. power-of-the-mean (POM) and exponential models, were used to fix the variance heterogeneity problem. Unlike the Box-Cox method, the variance models considered in this study were successful to deal simultaneously with both spatial correlation and heterogeneity of variance. The study shows that stage-wise analysis is a suitable approach for practical analysis of MET, GS and GWAS analysis. Single-stage and two-stage analysis of MET yield very similar results. Stage-wise analysis can be nearly as efficient as single-stage analysis when using optimal weighting, i.e., fully-efficient weighting. Spatial variation and within-trial variance heterogeneity are common in MET data. Download
    Genetic architecture of maize chlorotic mottle virus and maize lethal necrosis through GWAS, linkage analysis and genomic prediction in tropical maize germplasm
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    Analysis of the genetic architecture of MCMV and MLN resistance in maize doubled-haploid populations revealed QTLs with major effects on chromosomes 3 and 6 that were consistent across genetic backgrounds and environments. Two major-effect QTLs, qMCMV3-108/qMLN3-108 and qMCMV6-17/qMLN6-17, were identified as conferring resistance to both MCMV and MLN. Download
    Heterogeneous seed access and information exposure: implications for the adoption of drought-tolerant maize varieties in Uganda
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    Frequent droughts in sub-Saharan Africa imply water stress for rainfed agriculture and, ultimately, food insecurity, underlining the region’s vulnerability to climate change. Yet, in the maize-growing areas, farmers have been given new droughtcoping options following the release and availability of drought-tolerant maize varieties (DTMVs). These varieties are being disseminated through the National Agricultural Research and Extension Systems in collaboration with seed companies; however, their adoption still appears somewhat modest, and empirical studies on their adoption potential and associated drivers are scarce. We use empirical data from Uganda to estimate the actual and potential adoption rates and the adoption determinants of DTMVs under information and seed access constraints. Adoption rates for DTMVs could have been up to 22% in 2015 instead of the observed sample adoption rate of 14% if the whole population had been exposed to them. The adoption rate could increase to 30% if seed were availed to the farming population and to 47% if seed were sold at a more affordable price to farmers. The observed adoption rate of 14% implies gaps in the potential adoption rates of 8%, 16%, and 33% because of a lack of awareness, a lack of seed access, and high seed prices, respectively. The findings underscore the role of both market and non-market-based approaches and the potential to further scale the cultivation of DTMVs in Uganda. Download
    Impacts of drought-tolerant maize varieties on productivity,risk,and resource use : EvidencefromUganda
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    Weather variability is an important source of production risk for rainfed agriculture in developing countries. This paper evaluates the impacts of the adoption of drought-tolerant maize varieties on average maize yield,yield stability, risk exposure and resource use in rainfed smallholder maize farming. The study uses cross-sectional farm household-level data,collected from a sample of 840 farm households in Uganda. The adoption of drought tolerant maize varieties increased yield by 15% and reduced the probability of crop failure by 30%. We further show that the adoption of these varieties increased investments in maize production at the extensive margin through maize area increase and to a more limited extent at the intensive margin through mechanization. The findings show promise for further uptake and scaling of drought-tolerant maize varieties for increased productivity,reduced risk, and the transformation of the maize sector. Download
    Impact of adoption of drought-tolerant maize varieties on total maize production in south Eastern Zimbabwe
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    Drought is a huge limiting factor in maize production, mainly in the rain-fed agriculture of sub-Saharan Africa. In response to this threat, drought-tolerant (DT) maize varieties have been developed with an aim to ensure maize production under mild drought conditions. We conducted a study to assess the impact of smallholder farmers’ adoption of DT maize varieties on total maize production. Data for the study came from a survey of 200 randomly sampled households in two districts of Chiredzi and Chipinge in southeastern Zimbabwe. The study found that 93% of the households were growing improved maize varieties and that 30% of the sampled households were growing DT maize varieties. Total maize yield was 436.5 kg/ha for a household that did not grow DT maize varieties and 680.5 kg/ha for households that grew DT maize varieties. We control for the endogeneity of the DT adoption variable, by using the control function approach to estimate total maize production in a Cobb–Douglas model. The results show that households that grew DT maize varieties had 617 kg/ha more maize than households that did not grow the DT maize varieties. Given that almost all farmers buy their seeds in the market, a change in varieties to DT maize seeds gives an extra income of US$240/ha or more than nine months of food at no additional cost. This has huge implications in curbing food insecurity and simultaneously saving huge amounts of resources at the household and national levels, which are used to buy extra food during the lean season. Download
    Adoption of Drought Tolerant Maize Varieties under Rainfall Stress in Malawi
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    We examine adoption of drought tolerant (DT) maize varieties using a four-round panel dataset from six districts in Malawi. There is an increase in adoption of DT maize from 3% in 2006 to 43% in 2015 in our data. We focus on the effect of past drought exposure on adoption and the likelihood of DT maize being distributed under the Farm Input Subsidy Programme (FISP). Results show that past exposure to drought increases the probability of DT maize seed being distributed through FISP. Farmers who accessed maize seed subsidy coupons and were previously exposed to late season dry spells are more likely to use the seed subsidy coupon to redeem DT maize seed. The likelihood of adoption and adoption intensity (area under DT maize) are positively influenced by previous early season dry spells and access to seed subsidy. Previous late season droughts also positively affect adoption intensity. On the other hand, area share under DT maize is positively correlated with early season dry spells and past exposure to late season dry spells but negatively related to seed subsidy. FISP in Malawi appears to have stimulated adoption of DT maize directly through subsidy and indirectly through generating farmers’ experiences of the performance of DT varieties under drought conditions. Download
    Doubled haploid technology for line development in maize: technical advances and prospects
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    Doubled haploid (DH) technology has become an integral part of many commercial maize breeding programs as DH lines offer several economic, logistic and genetic benefits over conventional inbred lines. Further, new advances in DH technology continue to improve the efficiency of DH line development and fuel its increased adoption in breeding programs worldwide. The established method for maize DH production covered in this review involves in vivo induction of maternal haploids by a male haploid inducer genotype, identification of haploids from diploids at the seed or seedling stage, chromosome doubling of haploid (D0) seedlings and finally, selfing of fertile D0 plants. Development of haploid inducers with high haploid induction rates and adaptation to different target environments have facilitated increased adoption of DH technology in the tropics. New marker systems for haploid identification, such as the red root marker and high oil marker, are being increasingly integrated into new haploid inducers and have the potential to make DH technology accessible in germplasm such as some Flint, landrace, or tropical material, where the standard R1-nj marker is inhibited. Automation holds great promise to further reduce the cost and time in haploid identification. Increasing success rates in chromosome doubling protocols and/or reducing environmental and human toxicity of chromosome doubling protocols, including research on genetic improvement in spontaneous chromosome doubling, have the potential to greatly reduce the production costs per DH line. Download
    Genome-wide association study to identify genomic regions influencing spontaneous fertility in maize haploids
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    Efficient production and use of doubled haploid lines can greatly accelerate genetic gains in maize breeding programs. One of the critical steps in standard doubled haploid line production is doubling the haploid genome using toxic and costly mitosis inhibiting chemicals to achieve fertility in haploids. Alternatively, fertility may be spontaneously restored by natural chromosomal doubling, although generally at a rate too low for practical applications in most germplasm. This is the first large-scale genome-wise association study to analyze spontaneous chromosome doubling in haploids derived from tropical maize inbred lines. Induction crosses between tropicalized haploid inducers and 400 inbred lines were made, and the resulting haploid plants were assessed for haploid male fertility which refers to pollen production and haploid fertility which refers to seed production upon self-fertilization. A small number of genotypes were highly fertile and these fertility traits were highly heritable. Agronomic traits like plant height, ear height and tassel branch number were positively correlated with fertility traits. In contrast, haploid induction rate of the source germplasm and plant aspect were not correlated to fertility traits. Several genomic regions and candidate genes were identified that may control spontaneous fertility restoration. Overall, the study revealed the presence of large variation for both haploid male fertility and haploid fertility which can be potentially exploited for improving the efficiency of doubled haploid derivation in tropical maize germplasm.   Download
    Evaluating Maize Genotype Performance under Low Nitrogen Conditions Using RGB UAV Phenotyping Techniques
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    Maize is the most cultivated cereal in Africa in terms of land area and production, but low soil nitrogen availability often constrains yields. Developing new maize varieties with high and reliable yields using traditional crop breeding techniques in field conditions can be slow and costly. Remote sensing has become an important tool in the modernization of field-based high-throughput plant phenotyping (HTPP), providing faster gains towards the improvement of yield potential and adaptation to abiotic and biotic limiting conditions. We evaluated the performance of a set of remote sensing indices derived from red–green–blue (RGB) images along with field-based multispectral normalized difference vegetation index (NDVI) and leaf chlorophyll content (SPAD values) as phenotypic traits for assessing maize performance under managed low-nitrogen conditions. HTPP measurements were conducted from the ground and from an unmanned aerial vehicle (UAV). For the ground-level RGB indices, the strongest correlations to yield were observed with hue, greener green area (GGA), and a newly developed RGB HTPP index, NDLab (normalized difference Commission Internationale de I´Edairage (CIE) Lab index), while GGA and crop senescence index (CSI) correlated better with grain yield from the UAV. Regarding ground sensors, SPAD exhibited the closest correlation with grain yield, notably increasing in its correlation when measured in the vegetative stage. Additionally, we evaluated how different HTPP indices contributed to the explanation of yield in combination with agronomic data, such as anthesis silking interval (ASI), anthesis date (AD), and plant height (PH). Multivariate regression models, including RGB indices (R2 > 0.60), outperformed other models using only agronomic parameters or field sensors (R2 > 0.50), reinforcing RGB HTPP’s potential to improve yield assessments. Finally, we compared the low-N results to the same panel of 64 maize genotypes grown under optimal conditions, noting that only 11% of the total genotypes appeared in the highest yield producing quartile for both trials. Furthermore, we calculated the grain yield loss index (GYLI) for each genotype, which showed a large range of variability, suggesting that low-N performance is not necessarily exclusive of high productivity in optimal conditions. Download
    Multi-Site Bundling of Drought Tolerant Maize Varieties and Index Insurance
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    Drought Tolerant Maize Varieties (DTMV) and Rainfall Index Insurance (RII) are potential complements, though with limited empirical basis. We employ a multivariate spatial framework to investigate the potential for bundling DTMV with a simulated multi-site and multi-environment RII, designed to insure against mild, moderate and severe drought risk. We use yield data from on-farm trials conducted by the International Maize and Wheat Improvement Center (CIMMYT) and partners over 49 locations in Eastern and Southern Africa spanning 8 countries and 5 mega-environments (dry lowland, dry mid altitude, wet lower mid altitude, low wetland and wet upper mid altitude) in which 19 different improved maize varieties including DTMV were tested at each location. Spatially correlated daily rainfall data are generated from a first-order two-state Markov chain process and used to calibrate the index and predict yields with a hierarchical Bayes multivariate spatial model. Results show high variation in the performance and benefits of different bundles which depend on the maize variety, the risk layer insured, and the type of environment, with high chances of selecting a sub-optimal and unattractive contract. We find that complementing RII with a specific DTMV produces contracts with lower premiums and higher guaranteed returns especially in dry lowland increasing the chances of scaling up RII within this environment. Download
    Maize lethal necrosis and the molecular basis of variability in concentrations of the causal viruses in co-infected maize plant
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    Maize lethal necrosis (MLN) disease is new to Africa. First report was in Kenya in 2012, since then the disease has rapidly spread to most parts of eastern and central Africa region including Tanzania, Burundi, DRC Congo, Rwanda, Uganda, Ethiopia and similar symptoms were observed in South Sudan. Elsewhere, the disease was caused by infection of Maize Chlorotic Mottle Virus (MCMV) in combination with any of the potyviruses namely; maize dwarf mosaic virus (MDMV), sugarcane mosaic virus (SCMV) and tritimovirus wheat streak mosaic virus (WSMV). In Africa, the disease occurs due to combined infections of maize by MCMV and SCMV, leading to severe yield losses. Efforts to address the disease spread have been ongoing. Serological techniques including enzyme-linked immuno-sorbent assay (ELISA), polymerase chain reaction (PCR), genome-wide association (GWAS) mapping and next generation sequencing have been effectively used to detect and characterize MLN causative pathogens. Various management strategies have been adapted to control MLN including use of resistant varieties, phytosanitary measures and better cultural practices. This review looks at the current knowledge on MLN causative viruses, genetic architecture and molecular basis underlying their synergistic interactions. Lastly, some research gaps towards MLN management will be identified. The information gathered may be useful for developing strategies towards future MLN management and maize improvement in Africa. Download
    Productivity and production risk effects of adopting drought-tolerant maize varieties in Zambia
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    Productivity and production risks affect the use of agricultural production practices and inputs, particularly in developing countries. This paper aims to investigate the effects of adopting drought-tolerant maize varieties (DTMVs) on farm productivity,yield variance and downside risk exposure of maize growing households of Zambia. The study revealed that DTMV adoption increases maize yield by 15 per cent and reduces the risk of crop failure : reducing yield variance by 38 percent and exposure to downside risk by 36 percent. This study establishes the benefits of DTMV adoption in Zambia with regards to productivity, yield stability and downside risk in the face of climate change. Results from this study underscore the need for more concerted efforts to scale-out DTMVs for both maize productivity enhancement and for risk mitigation against weather shocks.   Download
    Western Seed case study
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    “Introducing a new maize variety needs a great deal of investment. You need to build a convincing business case for varietal turnover. Some new varieties may do well for certain traits, but there are other factors other than yield to consider, for instance, producibility, cost of seed production and farmers preferences.” says Saleem Esmail, CEO of Western Seed. Western Seed hybrids help smallholder farmers like Margaret Wafula and the Kaita family in western Kenya, get good maize harvests despite the numerous challenges like drought and diseases. Read more about the Western Seed case study here. Download
    Equator Seeds Case study
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    “80 percent of farmers in northern Uganda still use the farm-saved or recycled seed, which we consider as our biggest competitor. Through demonstrations and our local seed marketing network, farmers can see how well the drought and disease tolerant hybrid UH5051 performs, even under erratic climate. This has helped them to gradually adopt our improved seed.” says Equator Seeds CEO, Tonny Okello. Discover this successful partnership between STMA and Equator Seeds to reach out maize smallholder farmers in Northern Uganda and South Sudan to improve their productivity and resilience here Download
    Maize Ear Digital Imaging for Yield Components Assessment
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    In Sub-Saharan Africa, many food security programs aim to increase crop yields by developing and disseminating better seeds and agronomy to millions of smallholder farmers. In the case of maize, research and development organizations use key indicators like grain yield, or maize cob number and size to understand the performance of the maize plant under different environmental conditions. But these indicators are still labor-intensive and expensive to measure. CIMMYT has developed a digital imaging tool called Maize Ear Analyzer that collects maize cob and grain parameters 90% faster than traditional methods (Makanza et al, 2018). This imaging tool can be adapted to other crops. Download
    Gender-Responsive Budgeting Tool for the Promotion of Improved Maize Seed in Africa
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    Correct citation: Adam, R., Kandiwa, V. and Muindi, P. 2018. Gender-Responsive Budgeting Tool for the Promotion of Improved Maize Seed in Africa. Mexico, CIMMYT. Abstract: This tool is a decision-making guide for those seed companies who are seeking to make a wider population of farmers aware of the technologies they produce. The idea is to put your money where your potential market lies. The underlying rationale for this tool is that no single approach is able to reach all men and women farmers effectively. Similarly, while some approaches lend themselves well to reaching a wider population, others tend to be more effective in reaching specific demographic groups. This tool should be used alongside the gender-responsive approaches for the promotion of improved maize seed in Africa guide. Download
    Gender-Responsive Approaches for the Promotion of Improved Maize Seed in Africa
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    Correct citation: Kandiwa, V., Adam, R., Lweya, K., Setimela, P., Badstue, L. and Muindi, P. 2018. Gender-Responsive Approaches for the Promotion of Improved Maize Seed in Africa. Mexico, CIMMYT. Adoption of improved maize seed is very important for better productivity and livelihoods for the smallholder farmers in sub-Saharan Africa, where adoption rates for improved maize seed varieties are generally low. There is a great variability in adoption intensity and adoption rates across regions and demographic groups.  Several studies have revealed that women farmers are less likely to use improved seed than men, leading to lower yields. These gender gaps represent real costs to households, seed companies, agro-dealers and society. This publication provides basic guidelines on how to create awareness about improved maize seed varieties in ways that enhance farmers’ decision-making process and bridge knowledge gaps between men and women. It is complemented by tools for gender-sensitive crop variety field demonstrations, data collection from field days, and gender-responsive budgeting for creating awareness. These guidelines target public and private organizations that are involved in promoting improved seed varieties. Download

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