Akhunov E.D.,University of California at Davis |
Akhunova A.R.,University of California at Davis |
Anderson O.D.,U.S. Department of Agriculture |
Anderson J.A.,University of Minnesota |
And 31 more authors.
BMC Genomics | Year: 2010
Background: A genome-wide assessment of nucleotide diversity in a polyploid species must minimize the inclusion of homoeologous sequences into diversity estimates and reliably allocate individual haplotypes into their respective genomes. The same requirements complicate the development and deployment of single nucleotide polymorphism (SNP) markers in polyploid species. We report here a strategy that satisfies these requirements and deploy it in the sequencing of genes in cultivated hexaploid wheat (Triticum aestivum, genomes AABBDD) and wild tetraploid wheat (Triticum turgidum ssp. dicoccoides, genomes AABB) from the putative site of wheat domestication in Turkey. Data are used to assess the distribution of diversity among and within wheat genomes and to develop a panel of SNP markers for polyploid wheat.Results: Nucleotide diversity was estimated in 2114 wheat genes and was similar between the A and B genomes and reduced in the D genome. Within a genome, diversity was diminished on some chromosomes. Low diversity was always accompanied by an excess of rare alleles. A total of 5,471 SNPs was discovered in 1791 wheat genes. Totals of 1,271, 1,218, and 2,203 SNPs were discovered in 488, 463, and 641 genes of wheat putative diploid ancestors, T. urartu, Aegilops speltoides, and Ae. tauschii, respectively. A public database containing genome-specific primers, SNPs, and other information was constructed. A total of 987 genes with nucleotide diversity estimated in one or more of the wheat genomes was placed on an Ae. tauschii genetic map, and the map was superimposed on wheat deletion-bin maps. The agreement between the maps was assessed.Conclusions: In a young polyploid, exemplified by T. aestivum, ancestral species are the primary source of genetic diversity. Low effective recombination due to self-pollination and a genetic mechanism precluding homoeologous chromosome pairing during polyploid meiosis can lead to the loss of diversity from large chromosomal regions. The net effect of these factors in T. aestivum is large variation in diversity among genomes and chromosomes, which impacts the development of SNP markers and their practical utility. Accumulation of new mutations in older polyploid species, such as wild emmer, results in increased diversity and its more uniform distribution across the genome. © 2010 Akhunov et al; licensee BioMed Central Ltd.
Manda J.,International Institute Of Tropical Agriculture |
Gardebroek C.,Wageningen University |
Khonje M.G.,International Institute Of Tropical Agriculture |
Alene A.D.,International Institute Of Tropical Agriculture |
And 2 more authors.
Food Security | Year: 2016
Using household survey data from a sample of 810 households, this paper analyses the determinants of children’s nutritional status and evaluates the impacts of improved maize varieties on child malnutrition in eastern Zambia. The paper uses an endogenous switching regression technique, combined with propensity score matching, to assess the determinants of child malnutrition and impacts of improved maize varieties on nutritional status. The study finds that child nutrition worsens with the age of the child and improves with education of household head and female household members, number of adult females in the household, and access to better sanitation. The study also finds a robust and significant impact of improved maize varieties on child malnutrition. The empirical results indicate that adoption of improved maize varieties reduces the probability of stunting by an average of about 26 %. © 2015, Springer Science+Business Media Dordrecht and International Society for Plant Pathology.
Khonje M.,International Institute Of Tropical Agriculture |
Manda J.,International Institute Of Tropical Agriculture |
Alene A.D.,International Institute Of Tropical Agriculture |
Kassie M.,The International Maize and Wheat Improvement Center
World Development | Year: 2015
This paper analyzes the adoption and welfare impacts of improved maize varieties in eastern Zambia using data obtained from a sample of over 800 farm households. Using both propensity score matching and endogenous switching regression models, the paper shows that adoption of improved maize leads to significant gains in crop incomes, consumption expenditure, and food security. Results further show that improved maize varieties have significant poverty-reducing impacts in eastern Zambia. The paper concludes with implications for policies to promote adoption and impacts of modern varieties in Zambia. © 2014 Elsevier Ltd.
Kassie M.,The International Maize and Wheat Improvement Center |
Teklewold H.,CIMMYT |
Marenya P.,CIMMYT |
Jaleta M.,CIMMYT |
Journal of Agricultural Economics | Year: 2015
Employing nationally representative data, we investigate the impact of Sustainable Intensification Practices (SIPs) on farm households' food security, downside risk and the cost of risk in Malawi. The analysis relies on a flexible moment-based specification of a stochastic production function in a multinomial endogenous switching regression framework to correct for the selection bias stemming both from observed and unobserved heterogeneity. A quantile moment approach is used to estimate the cost of risk. After controlling for the effects of unobserved heterogeneity and several observable variables on maize production and downside risk functions, estimation results show that the adoption of SIPs increases food security and reduces downside risk exposure and the cost of risk. We estimate greater food security and larger reduction in downside risk from simultaneous adoption of both crop diversification (maize-legume intercropping and rotations) and minimum tillage, suggesting that there are complementary benefits from these practices. We find most of the cost of risk comes from exposure to downside risk. Our findings imply that in dealing with production risks development agents should encourage the adoption of agronomic and resource-management practices along with other risk mitigation and food security improving strategies. © 2015 The Agricultural Economics Society.
News Article | January 29, 2016
Plant scientists at Lancaster University, Rothamsted Research, and The International Maize and Wheat Improvement Center (CIMMYT) have been investigating a naturally occurring plant enzyme known as Rubisco to explore its ability to boost photosynthesis and increase crop yields. In a new paper published this month, the team measured photosynthesis in 25 genotypes of wheat—including wild relatives of bread wheat (Triticum aestivum)—and found variation exists even amongst closely related genotypes. Each type was surveyed to identify superior Rubisco enzymes for improving photosynthesis. Two of the most efficient were Rubisco from plants known as Aegilops cylindrica (jointed goatgrass) and Hordeum vulgare (barley), which both showed promising Rubisco catalytic properties that should be explored in the context of improving photosynthesis, and ultimately grain yield, in wheat. Models suggest that incorporating the new enzymes into wheat could increase photosynthesis by up 20% under some field conditions. Wheat is a crucial source of food, providing more than 20 per cent of the calories consumed worldwide. And with projections that the world population will rise to over nine billion by the year 2050, the pressure is on to meet global demand for food. Professor Martin A. J. Parry of the Lancaster Environment Centre (LEC) said: "Improving the efficiency of photosynthesis—the way crops turn carbon dioxide in our atmosphere into everything we can eat—may seem ambitious but for us it offers the best opportunity for producing the scale of change in crop yield that we need to feed a growing global population in a changing world climate." Elizabete Carmo-Silva, LEC lecturer in plant sciences for food security, said: "Both jointed grass and barley are regarded as valuable genetic resources for improving wheat disease resistance, our research suggests that they can also be used to improve biomass production." Research associates Anneke Prins and Doug Orr conducted the experimental work which was jointly funded by CIMMYT (W4031.11 Global Wheat Program) and by Realizing Increased Photosynthetic Efficiency, a project funded by the Bill & Melinda Gates Foundation and led by the University of Illinois at the Carl R. Woese Institute for Genomic Biology. "This is an exciting piece of work showing that Rubisco catalytic properties vary in close relatives of wheat," Orr said. "As part of the RIPE project, we are screening a wide range of species from across the globe, and aim to identify variation that will enable improving photosynthesis and biomass production in rice, cassava and soybean." Explore further: Algal genes may boost efficiency, yield in staple crops More information: The paper 'Rubisco catalytic properties of wild and domesticated relatives provide scope for improving wheat photosynthesis' was published in the Journal of Experimental Botany Advance Access.
PubMed | Shanghai Academy of Agricultural science SAAS, Indian International Crops Research Institute for the Semi Arid Tropics and The International Maize and Wheat Improvement Center
Type: Journal Article | Journal: PloS one | Year: 2016
We aimed to identify quantitative trait loci (QTL) for secondary traits related to grain yield (GY) in two BC1F2:3 backcross populations (LPSpop and DTPpop) under well-watered (4 environments; WW) and drought stressed (6; DS) conditions to facilitate breeding efforts towards drought tolerant maize. GY reached 5.6 and 5.8 t/ha under WW in the LPSpop and the DTPpop, respectively. Under DS, grain yield was reduced by 65% (LPSpop) to 59% (DTPpop) relative to WW. GY was strongly associated with the normalized vegetative index (NDVI; r ranging from 0.61 to 0.96) across environmental conditions and with an early flowering under drought stressed conditions (r ranging from -0.18 to -0.25) indicative of the importance of early vigor and drought escape for GY. Out of the 105 detected QTL, 53 were overdominant indicative of strong heterosis. For 14 out of 18 detected vigor QTL, as well as for eight flowering time QTL the trait increasing allele was derived from CML491. Collocations of early vigor QTL with QTL for stay green (bin 2.02, WW, LPSpop; 2.07, DS, DTPpop), the number of ears per plant (bins 2.02, 2.05, WW, LPSpop; 5.02, DS, LPSpop) and GY (bin 2.07, WW, DTPpop; 5.04, WW, LPSpop), reinforce the importance of the observed correlations. LOD scores for early vigor QTL in these bins ranged from 2.2 to 11.25 explaining 4.6 (additivity: +0.28) to 19.9% (additivity: +0.49) of the observed phenotypic variance. A strong flowering QTL was detected in bin 2.06 across populations and environmental conditions explaining 26-31.3% of the observed phenotypic variation (LOD: 13-17; additivity: 0.1-0.6d). Improving drought tolerance while at the same time maintaining yield potential could be achieved by combining alleles conferring early vigor from the recurrent parent with alleles advancing flowering from the donor. Additionally bin 8.06 (DTPpop) harbored a QTL for GY under WW (additivity: 0.27 t/ha) and DS (additivity: 0.58 t/ha). R2 ranged from 0 (DTPpop, WW) to 26.54% (LPSpop, DS) for NDVI, 18.6 (LPSpop, WW) to 42.45% (LPSpop, DS) for anthesis and from 0 (DTPpop, DS) to 24.83% (LPSpop, WW) for GY. Lines out-yielding the best check by 32.5% (DTPpop, WW) to 60% (DTPpop, DS) for all population-by-irrigation treatment combination (except LPSpop, WW) identified are immediately available for the use by breeders.
Neiff N.,The International Maize and Wheat Improvement Center |
Dhliwayo T.,The International Maize and Wheat Improvement Center |
Suarez E.A.,The International Maize and Wheat Improvement Center |
Burgueno J.,The International Maize and Wheat Improvement Center |
Trachsel S.,The International Maize and Wheat Improvement Center
Journal of Crop Improvement | Year: 2015
In light of anticipated climate change, we assessed the possibility to use an airborne platform to measure canopy temperature (CT) and the normalized differential vegetation index (NDVI) as well as the suitability of both traits for their use in breeding for tolerance to heat stress. We evaluated 71 subtropical maize (Zea maysL.) hybrids under heat stress and combined heat and drought stress in an environment with average temperatures of 29.8°C during the growing season and 31.2°C during the flowering period. Grain yield (GY) ranged from 0.33 to 4.19 Mg ha−1 under heat stress and from 0 to 1.37 Mg ha−1 under combined heat and drought stress, going along with increases in CT from 42.5°C to 49.5°C and decreases in NDVI from 0.54 to 0.48. The NDVI explained differences between and within treatments, while CT explained differences in GY among treatments and genotypes within the heat and drought stress treatment, as indicated by genetic correlations with GY. A principal component analysis was used to identify combinations of physiological characteristics associated with genotypic variation in GY. Results showed that selection gains for GY could be improved by 0.486 Mg ha−1 and 0.015 Mg ha−1 under heat and combined heat and drought stress, respectively, if selection is simultaneously carried out for GY, NDVI, and lower CT and shorter anthesis silking interval. We postulate that the use of selection indices, including CT and NDVI in conjunction with GY, will improve selection gains and increase cost efficiency of breeding programs. Copyright © Taylor & Francis Group, LLC.
Tefera T.,The International Maize and Wheat Improvement Center |
Kanampiu F.,The International Maize and Wheat Improvement Center |
De Groote H.,The International Maize and Wheat Improvement Center |
Hellin J.,The International Maize and Wheat Improvement Center |
And 6 more authors.
Crop Protection | Year: 2011
Traditional storage practices in developing countries cannot guarantee protection against major storage pests of staple food crops like maize, leading to 20-30% grain losses, particularly due to post-harvest insect pests and grain pathogens. As a result, smallholder farmers end up selling their grain soon after harvest, only to buy it back at an expensive price just a few months after harvest, falling in a poverty trap. The potential impact on poverty reduction and greater livelihood security will not be realized, however, if farmers are unable to store grains and sell surplus production at attractive prices. Apart from causing quantitative losses, pests in stored grain are also linked to aflatoxin contamination and poisoning. To address this problem, a metal silo was developed as a valid option and proven effective in protecting stored grains from attack by storage insect pests. A metal silo is a cylindrical structure, constructed from a galvanized iron sheet and hermetically sealed, killing any insect pests that may be present. The impact of metal silo technology in Africa, Asia and Latin America includes, improving food security, empowering smallholder farmers, enhancing income opportunities and job creation, and safeguarding the agro-ecosystems. The metal silo can be fabricated in different sizes, 100 kg-3000 kg holding capacity by trained local artisans, with the corresponding prices of $35 to $375. The use of metal silo, therefore, should be encouraged in order to prevent storage losses and enhance food security in developing countries. © 2010 Elsevier Ltd.
TRACHSEL S.,The International Maize and Wheat Improvement Center |
SAN VICENTE F.M.,The International Maize and Wheat Improvement Center |
SUAREZ E.A.,The International Maize and Wheat Improvement Center |
RODRIGUEZ C.S.,The International Maize and Wheat Improvement Center |
ATLIN G.N.,The International Maize and Wheat Improvement Center
Journal of Agricultural Science | Year: 2015
To support tropical maize (Zea mays L.) 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/m2 under 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/m2 to 0·45 at 11 plants/m2 under HN conditions and decreased from 0·44 at 5 plants/m2 to 0·42 at 9 plants/m2 under LN conditions. Harvest index was maximized at planting densities of 8·33 plants/m2 and 5·30 plants/m2 under HN and LN conditions, respectively, while grain yield was maximized at 9·93 plants/m2 and 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. Copyright © Cambridge University Press 2015
PubMed | The International Maize and Wheat Improvement Center
Type: Journal Article | Journal: TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik | Year: 2013
Investigations were made on the rye chromosome constitution and on the presence of telomeric heterochromatin in rye chromosomes of the 26 most widely and 24 most narrowly adapted triticale strains. Among widely adapted lines, 22 (85%) had a complete rye genome and four triticales only had chromosomal R-D genome substitutions. Twenty-three (96%) of the 24 most narrowly adapted triticales had substitutions between the chromosomes of the R and D genomes. The most widely adapted triticales accumulated fewer modified rye chromosomes in comparison to narrowly adapted lines. They had from one to three rye chromosomes with heterochromatic deletions: 46% of widely adapted lines had two modified rye chromosomes; 34% had three modified rye chromosomes, and 19% had a single modified rye chromosome. In widely adapted strains, the 1R, 4R, 5R and 6R modified chromosomes were observed; they were present in 80%, 73%, 50% and 11% of the cases, respectively. The most narrowly adapted triticales had from two to four modified rye chromosomes: 58% of the strains had three modified rye chromosomes; 29% had four modified rye chromosomes and 12% had two modified rye chromosomes. The modified 4R and 5R chromosomes were present in all of these lines. The 1R (modified), 6R (modified) and 7R (modified) were found in 83%, 25% and 16%, respectively, of the narrowly adapted strains.Results support the previous observations (Pilch 1980b) that a wide adaptation of hexaploid triticales is associated with the presence of the full potential of rye genome, and that it is independent of the amount of telomeric heterochromatin possessed by rye chromosomes.