International Maize and Wheat Improvement Center

About: International Maize and Wheat Improvement Center is a nonprofit organization based out in Texcoco, Mexico. It is known for research contribution in the topics: Population & Agriculture. The organization has 1976 authors who have published 4799 publications receiving 218390 citations.

Environmental consequences of agricultural commercialization in Asia

Abstract: Agroindustrialization and agricultural commercialization are both conse- quences of economic growth and urbanization. Commercialization of agricultural systems leads to greater market orientation; progressive substitution out of non-traded inputs for purchased inputs; and the decline of integrated farming systems. Agricultural commercialization can have both negative and positive impacts on the natural resource base. Higher opportunity cost of labor increases farmer reliance on herbicides for weed control, primarily for the staple crops. The use of insecticides and fungicides could also rise, especially for high value fruit and vegetable crops. Increased use of agricultural chemicals could lead to higher environmental and human health risks. On the other hand, global integration and the consequent rationalization of agricultural policies could have significant environmental benefits, especially in terms of a reduced rate of salinity build up and ground water depletion in irrigated environments. The extent to which positive environmental effects manifest themselves depends on both macroeconomic and microeconomic policy reforms.

Meta-analyses of QTL for grain yield and anthesis silking interval in 18 maize populations evaluated under water-stressed and well-watered environments

Abstract: Identification of QTL with large phenotypic effects conserved across genetic backgrounds and environments is one of the prerequisites for crop improvement using marker assisted selection (MAS). The objectives of this study were to identify meta-QTL (mQTL) for grain yield (GY) and anthesis silking interval (ASI) across 18 bi-parental maize populations evaluated in the same conditions across 2-4 managed water stressed and 3-4 well watered environments. The meta-analyses identified 68 mQTL (9 QTL specific to ASI, 15 specific to GY, and 44 for both GY and ASI). Mean phenotypic variance explained by each mQTL varied from 1.2 to 13.1% and the overall average was 6.5%. Few QTL were detected under both environmental treatments and/or multiple (>4 populations) genetic backgrounds. The number and 95% genetic and physical confidence intervals of the mQTL were highly reduced compared to the QTL identified in the original studies. Each physical interval of the mQTL consisted of 5 to 926 candidate genes. Meta-analyses reduced the number of QTL by 68% and narrowed the confidence intervals up to 12-fold. At least the 4 mQTL (mQTL2.2, mQTL6.1, mQTL7.5 and mQTL9.2) associated with GY under both water-stressed and well-watered environments and detected up to 6 populations may be considered for fine mapping and validation to confirm effects in different genetic backgrounds and pyramid them into new drought resistant breeding lines. This is the first extensive report on meta-analysis of data from over 3100 individuals genotyped using the same SNP platform and evaluated in the same conditions across a wide range of managed water-stressed and well-watered environments.

Conservation agriculture for sustainable intensification in South Asia

Abstract: Agriculture’s contribution to the Sustainable Development Goals requires climate-smart and profitable farm innovations. In the past decade, attention has been given to conservation agriculture as a ‘sustainable intensification’ strategy, although a lack of evidence-based consensus on the merits of conservation agriculture prevails in the context of intensive smallholder farming in South Asia. A meta-analysis using 9,686 paired site–year comparisons representing different indicators of cropping-system performance suggest significant (P < 0.05) benefits when conservation-agriculture component practices are implemented either separately or in tandem. For example, zero tillage with residue retention had a mean yield advantage of 5.8%, a water use efficiency increase of 12.6%, an increase in net economic return of 25.9% and a reduction of 12–33% in global warming potential, with more-favourable responses on loamy soils and in maize–wheat systems. Results suggest that there are opportunities to maximize expected benefits, and policymakers and development practitioners should continue to be appraised of the potential of CA for contributing to the Sustainable Development Goals in South Asia. Conservation agriculture prioritizes soil health and diverse cropping systems. This meta-analysis finds multiple benefits, including for water conservation and profitability, from conservation-agriculture practices in South Asia.

A sampling strategy for conserving genetic diversity when forming core subsets

Abstract: When forming core subsets, accessions from a collection are classified into clusters, and then samples are drawn from the clusters with the aim of maintaining the diversity of the collection. In a stratified sampling strategy, the allocation method provides a criterion for determining the number of accessions to be selected from each cluster. This paper proposes an allocation method (D method) and compares it with three other allocation methods (L, LD, and NY methods). In these allocation methods, the number of accessions sampled per cluster is proportional to (i) the mean of the Gower's distance between accessions within the cluster (D method), (ii) the logarithm of the cluster size (L method), (iii) the product of the cluster size times the mean Gower distance (NY method), and (iv) the product of the logarithm of the cluster size times the mean Gower distance (LD method). Five hundred independent stratified random samples with two sampling intensities (10 and 20%) were obtained from four datasets. The allocation methods were compared on the basis of three criteria: diversity of the samples, recovery of the range of variables in the sample, and variances of the samples. Results showed that the D method produced samples (i) with significantly more diversity than the other allocation methods, (ii) that recovered more of the range of the variables, (iii) with higher variances for the continuous variables than the other three methods, and (iv) with variances higher than the variance among accessions of the collection. A sampling intensity of 10% preserves the same or more variability than a sampling intensity of 20%.