Time filter

Source Type

Ertiro B.T.,Maize Research Institute Zemun Polje | Beyene Y.,International Maize and Wheat Improvement Center | Das B.,International Maize and Wheat Improvement Center | Mugo S.,International Maize and Wheat Improvement Center | And 5 more authors.
Plant Breeding | Year: 2017

Drought and poor soil fertility are among the major abiotic stresses affecting maize productivity in sub-Saharan Africa. Maize breeding efforts at the International Maize and Wheat Improvement Center (CIMMYT) have focused on incorporating drought stress tolerance and nitrogen-use efficiency (NUE) into tropical maize germplasm. The objectives of this study were to estimate the general combining ability (GCA) and specific combining ability (SCA) of selected maize inbred lines under drought stress (DS), low-nitrogen (LN) and optimum moisture and nitrogen (optimum) conditions, and to assess the yield potential and stability of experimental hybrids under these management conditions. Forty-nine experimental three-way cross hybrids, generated from a 7 × 7 line by tester crosses, and six commercial checks were evaluated across 11 optimum, DS and LN sites in Kenya in 2014 using an alpha lattice design with two replicates per entry at each site. DS reduced both grain yield (GY) and plant height (PH), while anthesis–silking interval (ASI) increased under both DS and LN. Hybrids ‘L4/T2’ and ‘L4/T1’ were found to be superior and stable, while inbreds ‘L4’ and ‘L6’ were good combiners for GY and other secondary traits across sites. Additive variance played a greater role for most traits under the three management conditions, suggesting that further progress in the improvement of these traits should be possible. GY under optimum conditions was positively correlated with GY under both DS and LN conditions, but GY under DS and LN was not correlated. Our results suggest the feasibility for simultaneous improvement in grain yield performance of genotypes under optimum, DS and LN conditions. © 2017 The Authors Plant Breeding Published by Blackwell Verlag GmbH


Kone B.,Africa Rice Center | Kone B.,University of South Africa | Sylvester O.,African Agricultural Technology Foundation AATF | Diatta S.,Africa Rice Center | And 3 more authors.
Archives of Agronomy and Soil Science | Year: 2011

In West Africa, two-thirds of upland rice is grown on acidic phosphorus (P)- deficient soils. Phosphorus is one of the most limiting-nutrients affecting crop productivity. A three-year field experiment was conducted on a Ferralsol in Côte d'Ivoire to study the response of four interspecific rice cultivars and a sativa (control cultivar) to Tilemsi phosphate rock (PR) and soluble triple superphosphate (TSP) fertilizer. PR was applied at 0, 150, 300, and 450 kg ha-1 P once in the first year and residual effects were measured in the following years. TSP (0, 50, 100 and 150 kg ha-1 P) was applied yearly. More significant yield increasing (38%) was observed in the second year. Annual application of 50 kg P ha-1 as TSP or a one-time application of 150 kg P ha-1 as PR was the optimum rate for the production of all cultivars. Higher rates of P from TSP (100 and 150 kg P ha-1) gave 2-3 times greater residual P in soil than the optimum rate, inducing no further response of rice. Two interspecific cultivars were identified as the most acid- and low P-tolerant cultivars for improving rice production in West Africa humid forest zone. © 2011 Taylor & Francis.


Toure A.,Africa Rice Center | Rodenburg J.,Africa Rice Center | Saito K.,Africa Rice Center | Oikeh S.,African Agricultural Technology Foundation AATF | And 3 more authors.
Weed Technology | Year: 2011

Weeds are a major constraint to rice production in labor-limited, upland rice-based systems in West Africa. The effects of weeding regimes and rice cultivars on weed growth and rice yield were investigated at two upland locations (Abomey-Calavi and Niaouli) in the degraded coastal savanna zone of Benin in 2005 and 2006 with below-average rainfall. Four weeding regimes (hoe weeding at 21 d after sowing [DAS], delayed hoe weeding at 31 DAS, hoe weeding at 21 and 42 DAS, and a no weeding control) were the main plot treatments. Cultivars comprising three interspecific upland rice cultivars (NERICA 1, NERICA 2, and NERICA 7) and the parents (Oryza sativa WAB56-104 and O. glaberrima CG14) were tested in subplots. The most dominant weed species identified were Jamaican crabgrass, Mariscus, and silver spinach. Rice yield was generally low because of drought stress; none of the experiments had a higher mean yield than 1,400 kg ha -1 across cultivars. Across cultivars, the best weeding regimes in terms of weed control and rice yields were single weeding at 31 DAS (W31) and double weeding at 21 and 42 DAS (W21+42). Under these weeding regimes, WAB56-104 out-yielded the three NERICA cultivars. CG14 showed the strongest weed suppressive ability (WSA) in Abomey-Calavi but did not have strong WSA in Niaouli because of lower biomass accumulation. WSA of WAB56-104 was similar to that of the three NERICA cultivars. Single weeding at 31 DAS, together with the use of cultivars with good adaptation to unfavorable rice growing conditions, would increase land and labor productivity of upland rice-based systems in West Africa. © Weed Science Society of America.


Saito K.,Africa Rice Center | Azoma K.,Africa Rice Center | Oikeh S.O.,African Agricultural Technology Foundation AATF
Soil and Tillage Research | Year: 2010

Intensifying upland rice cultivation has resulted in increased weed pressure and declining soil fertility and rice yield in West Africa. Integrated crop management technologies are needed for enhancing rice productivity. A field experiment was conducted from 2006 to 2008 in a Typic Haplustult soil in southern Benin to identify the optimal seeding date of stylo relay-cropped into upland rice, and to evaluate the effects of fallow treatment and tillage management on rice yield, weed biomass and soil properties. Stylosanthes guianensis (stylo), a legume species, was used as a short-term fallow crop. Rice was grown once each year and stylo was seeded during the wet season and grown until the next rice-growing season. The effects of fallow treatment and tillage management (no-tillage vs. manual-tillage) on weed biomass during the rice-growing season were evaluated in 2007 and 2008, whereas the effects on rice yield were examined in 2007 alone. Results indicated that stylo can be established as a relay crop with upland rice about 10 days after rice seeding. Stylo fallow reduced weed biomass by 71% and 95% and increased total biomass (weed + stylo + litter) by 594% and 107% at the end of the dry seasons in 2007 and 2008, respectively. No-tillage without stylo fallow increased weed biomass by 62-202% over manual-tillage during the rice-growing seasons, whereas stylo fallow reduced weed biomass by 45-83% and 11-36%, respectively, under no-tillage and manual-tillage management. There were no significant effects of fallow treatment and tillage management on soil organic C, total N, inorganic N and extractable P. Rice yields following stylo fallow were 0.7 Mg ha -1 higher than after the natural fallow. Manual-tillage increased rice yield by 0.6 Mg ha -1 over no-tillage. Manual-tillage combined with stylo fallow can be recommended to smallholder farmers for improving upland rice productivity. © 2010 Elsevier B.V. All rights reserved.


Sserumaga J.P.,National Crops Resources Research Institute NaCRRI | Oikeh S.O.,African Agricultural Technology Foundation AATF | Mugo S.,International Maize and Wheat Improvement Center | Asea G.,National Crops Resources Research Institute NaCRRI | And 4 more authors.
Euphytica | Year: 2016

In vivo production of maternal haploid plants and advancement in chromosome doubling technology has led to rapid production of doubled haploid homozygous lines. These in turn have boosted rapid advancement in most breeding programs. This has resulted in production of a large number of maize hybrids which need testing across production environments to select the most suitable hybrids for release and cultivation. The objective of this study was to assess the genotype × environment interactions (GE) for grain yield and other agronomic traits and evaluate the performance of 44 recently developed doubled haploids (DH) testcross hybrids along with six checks across five locations in Uganda. Significant mean squares for environment (E), genotype (G) and GE were observed for all studied traits. Environment explained 46.5 % of the total variance, while G and GE contributed 13.2 and 7.2 %, respectively. Genetic correlations among locations were high (0.999), suggesting little GE among environments. The 10 best testcross hybrids had a 49.2 % average grain yield advantage over the six checks at all locations. DH hybrids CKHDHH0887, CKDHH0878, CKDHH0859, WM1210, CKDHH0858, and WM1214 were the most stable, across locations. The DH testcross hybrids produced higher grain yield and possessed acceptable agronomic traits compared to the commercial hybrids developed earlier. Use of the best DH testcross hybrids, well targeted to the production environments, could boost maize production among farmers. © 2015, Springer Science+Business Media Dordrecht.


Beyene Y.,International Maize and Wheat Improvement Center | Semagn K.,International Maize and Wheat Improvement Center | Mugo S.,International Maize and Wheat Improvement Center | Prasanna B.M.,International Maize and Wheat Improvement Center | And 7 more authors.
Euphytica | Year: 2016

A marker-assisted recurrent selection (MARS) program was undertaken in sub-Saharan Africa to improve grain yield under drought-stress in 10 biparental tropical maize populations. The objectives of the present study were to evaluate the performance of C1S2-derived hybrids obtained after three MARS cycles (one cycle of recombination (C1), followed by two generations of selfing (S2), and to study yield stability under both drought-stress (DS) and well-watered (WW) conditions. For each of the 10 populations, we evaluated hybrids developed by crossing 47–74 C1S2 lines advanced through MARS, the best five S5 lines developed through pedigree selection, and the founder parents with a single-cross tester from a complementary heterotic group. The hybrids and five commercial checks were evaluated in Kenya under 1–3 DS and 3–5 WW conditions with two replications. Combined across DS locations, the top 10 C1S2-derived hybrids from each of the 10 biparental populations produced 0.5–46.3 and 11.1–55.1 % higher mean grain yields than hybrids developed using pedigree selection and the commercial checks, respectively. Across WW locations, the best 10 hybrids derived from C1S2 of each population produced 3.4–13.3 and 7.9–36.5 % higher grain yields than hybrids derived using conventional pedigree breeding and the commercial checks, respectively. Mean days to anthesis of the best 10 C1S2 hybrids were comparable to those of hybrids developed using the pedigree method, the founder parents and the commercial checks, with a maximum difference of 3.5 days among the different groups. However, plant height was significantly (P < 0.01) different in most pairwise comparisons. Our results showed the superiority of MARS over pedigree selection for improving diverse tropical maize populations as sources of improved lines for stress-prone environments and thus MARS can be effectively integrated into mainstream maize breeding programs. © 2015, The Author(s).


PubMed | African Agricultural Technology Foundation AATF, International Maize and Wheat Improvement Center, Monsanto Corporation and CIMMYT
Type: | Journal: Euphytica: Netherlands journal of plant breeding | Year: 2016

A marker-assisted recurrent selection (MARS) program was undertaken in sub-Saharan Africa to improve grain yield under drought-stress in 10 biparental tropical maize populations. The objectives of the present study were to evaluate the performance of C


Thomson J.A.,University of Cape Town | Shepherd D.N.,University of Cape Town | Mignouna H.D.,African Agricultural Technology Foundation AATF
AgBioForum | Year: 2010

A number of crops with a variety of traits are being developed by public-private partnerships in sub-Saharan Africa. These include maize that is resistant to the parasitic weed, Striga; tolerant to drought, and resistant to the African endemic maize streak virus. Others in the pipeline are insect-resistant cowpea and potato, as well as nutritionally-enriched sorghum. Some of these are undergoing field trials in various parts of the sub-continent. However, the South African regulatory authorities denied permission for release of the genetically modified potato and for glasshouse trials of the sorghum. After an appeal against the latter decision, permission was eventually given after two years. It remains to be seen how regulatory authorities respond to requests regarding the other crops. © 2010 AgBioForum.


Salas Fernandez M.G.,Iowa State University | Okeno J.A.,Iowa State University | Okeno J.A.,African Agricultural Technology Foundation AATF | Mutegi E.,Ohio State University | And 3 more authors.
Conservation Genetics | Year: 2014

Understanding the extent of gene exchange between cultivated sorghum and its wild/weedy relatives and the evolutionary processes (including farmers’ practices) that act to shape the structure of genetic diversity within and between them is an important aspect for germplasm conservation strategies, biosafety risk assessment, and crop improvement programs. In this study, molecular characterization and genetic diversity analyses were conducted on wild, weedy and cultivated sorghums collected at a local-scale in a traditional farming system in the Lambwe Valley of western Kenya. Nine simple sequence repeat (SSR) markers were used to genotype 294 cultivated sorghum and 200 wild sorghum individuals. The nine SSR markers were highly polymorphic with a number of alleles that varied from 2 to 19. Overall, wild sorghums had higher genetic diversity, observed heterozygosity, total number of alleles, polymorphic information content and more genotypes per locus than the cultivated types. A Mantel test demonstrated that there was significant isolation-by-distance for wilds and cultivated materials. STRUCTURE, cluster and principal coordinate analyses consistently assigned wild and cultivated individuals to different groups but failed to place hybrids/weedy types as a single separate group from wilds. Our results provide strong evidence of significant genetic diversity retained within wilds, larger divergence between wild and cultivated materials and reduced gene flow than those previously reported in Kenya. These results demonstrate the value of the Lambwe Valley region as a genetic reservoir and the importance to conduct genetic diversity studies at the local scale to design and execute appropriate in situ conservation programs and policies. © 2014, Springer Science+Business Media Dordrecht.


Nang'ayo F.,African Agricultural Technology Foundation AATF | Simiyu-Wafukho S.,African Agricultural Technology Foundation AATF | Oikeh S.O.,African Agricultural Technology Foundation AATF
Transgenic Research | Year: 2014

Globally, transgenic or genetically modified (GM) crops are considered regulated products that are subject to regulatory oversight during trans-boundary movement, testing and environmental release. In Africa, regulations for transgenic crops are based on the outcomes of the historic Earth Summit Conference held in Rio, Brazil two decades ago, namely, the adoption of the Convention on Biological Diversity (CBD) and the subsequent adoption of the Cartagena Protocol on Biosafety. To exploit the potential benefits of transgenic crops while safeguarding the potential risks on human health and environment, most African countries have signed and ratified the CBD and the Cartagena Protocol on Biosafety. Consequently, these countries are required to take appropriate legal, administrative and other measures to ensure that the handling and utilization of living modified organisms are undertaken in a manner that reduces the risks to humans and the environment. These countries are also expected to provide regulatory oversight on transgenic crops through functional national biosafety frameworks (NBFs). While in principle this approach is ideal, NBFs in most African countries are steeped in a host of policy, legal and operational challenges that appear to be at cross-purposes with the noble efforts of seeking to access, test and deliver promising GM crops for use by resource-limited farmers in Africa. In this paper we discuss the regulatory challenges faced during the development and commercialization of GM crops based on experiences from countries in Sub-Saharan Africa. © 2014, Springer International Publishing Switzerland.

Loading African Agricultural Technology Foundation AATF collaborators
Loading African Agricultural Technology Foundation AATF collaborators