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.

Impact of direct sowing mulch-based cropping systems on soil carbon, soil erosion and maize yield

Abstract: We studied the impact of direct seeding mulch-based cropping systems (DMC) on soil characteristics and maize production compared with conventional tillage management (CT) in the semi-arid region of western Mexico Mulch treatments included 0, 15, 3 and 45 Mg ha-1 of added surface crop residues The study was carried out from 1994 to 1998 on a Dystric Cambisol soil in La Tinaja in the state of Jalisco Water runoff, soil erosion, soil C changes, maize aboveground biomass and grain yield were monitored on field plots The results show that mulch treatments reduced annual water runoff losses by 10 to 50% relative to the conventional tillage treatment depending on residue amounts, slope and year Soil erosion losses were reduced by 50 to 90% Over a 5-year period soil carbon levels under mulch increased by 23 to 29% compared with conventional tillage, mainly due to increased crop residue inputs and reduced soil carbon erosion under mulch treatment In the year with the most intense rainfall (1997), the conventional treatment lost about 800 kg of C ha-1 ie 2 to 7 times greater than mulch treatments Maize grain yields were greater by 170 to 190% under mulch Yield increases under mulch occurred each year, notably due to improved water and nutrient use efficiency Potential yield benefits under mulch in the longer term due to build-up of soil organic matter and reduction of soil erosion were not obvious in our experiment Overall, even small amounts of surface residue are effective at sustaining rainfed maize productivity under the semi-arid conditions of western Mexico The short-term yield benefits are a promising factor for adoption of direct seeding mulch-based systems in the region (Resume d'auteur)

Choosing evaluation environments to increase wheat grain yield under drought conditions

Abstract: A key question in genetic improvement of yield under drought stress is how to choose environments to evaluate and identify genotypes that yield well under drought. The objective of this study was to compare various moisture regimes as evaluation environments for wheat (Triticum aestivum L. emend. Thell.) germplasm, based on performance of specific genotypes and on expected genetic advance from direct and indirect selection. The test included 12 new, experimental spring bread wheat genotypes selected for high yield under both full and reduced irrigation in Mexico and four cultivars selected in and adapted to each of the following moisture regimes: (i) full irrigation (FI), (ii) late season drought (LD), (iii) early season drought (ED), (iv) residual moisture (RM), and (v) sporadic drought [...]

Simulation-based analysis of effects of Vrn and Ppd loci on flowering in wheat

Abstract: Cereal production is strongly infl uenced by fl owering date. Wheat (Triticum aestivum L.) models simulate days to fl ower by assuming that development is modifi ed by vernalization and photoperiodism. Cultivar differences are parameterized by vernalization requirement, photoperiod sensitivity, and earliness per se. The parameters are usually estimated by comparing simulations with fi eld observations but appear estimable from genetic information. For wheat, the Vrn and Ppd loci, which affect vernalization and photoperiodism, were logical candidates for estimating parameters in the model CSM-Cropsim-CERES. Two parameters were estimated conventionally and then re-estimated with linear effects of Vrn and Ppd. Flowering data were obtained for 29 cultivars from international nurseries and divided into calibration (14 locations) and evaluation (34 locations) sets. Simulations with a generic cultivar explained 95% of variation in fl owering for calibration data (10 d RMSE) and 89% for evaluation data (10 d RMSE), indicating the large effect of environment. Nonetheless, for the calibration data, the gene-based model explained 29% of remaining variation, and the conventional model, 54%. For the evaluation data, the gene-based model explained 17% of remaining variation, and the conventional model, 27%. Gene-based prediction of wheat phenology appears feasible, but more extensive genetic characterization of cultivars is needed.

Quantitative trait loci for slow-rusting resistance in wheat to leaf rust and stripe rust identified with multi-environment analysis

Abstract: Rust diseases are a major cause of yield loss in wheat worldwide, and are often controlled through the incorporation of resistance genes using conventional phenotypic selection methods. Slow-rusting resistance genes are expressed quantitatively and are typically small in genetic effect thereby requiring multiple genes to provide adequate protection against pathogens. These effects are valuable and are generally considered to confer durable resistance. Therefore an understanding of the chromosomal locations of such genes and their biological effects are important in order to ensure they are suitably deployed in elite germplasm. Attila is an important wheat grown throughout the world and is used as a slow-rusting donor in international spring wheat breeding programs. This study identified chromosomal regions associated with leaf rust and stripe rust resistances in a cross between Attila and a susceptible parent, Avocet-S, evaluated over 3 years in the field. Genotypic variation for both rusts was large and repeatable with line-mean heritabilities of 94% for leaf rust resistance and 87% for stripe rust. Three loci, including Lr46/Yr29 on chromosome 1BL, were shown to provide resistance to leaf rust whereas six loci with small effects conferred stripe rust resistance, with a seventh locus having an effect only by epistasis. Disease scoring over three different years enabled inferences to be made relating to stripe rust pathogen strains that predominated in different years.

Stakeholder perception of wheat production constraints, capacity building needs, and research partnerships in developing countries

Abstract: In order to update the available information on the main current and future constraints on wheat production and human capacity development, a survey covering nineteen developing countries, including major wheat producers, was conducted prior to the 2006 International Symposium on Increasing Wheat Yield Potential in Ciudad Obregon, Mexico. The results emphasize the substantial yield losses associated with a number of critical abiotic, biotic and socioeconomic constraints, and indicate their global prevalence. The most important constraints on wheat production are heat (affecting up to 57% of the entire wheat area in surveyed countries), competition with weeds, and diseases (both affecting up to 55% of wheat area). Of the socioeconomic constraints listed and evaluated by respondents, access to mechanization and availability of credit were the most often highlighted. The most-reported infrastructural constraints were insufficient resources for field station operations. When evaluating the importance of research partnerships to achieve national wheat program goals, respondents from all 19 countries assigned the highest importance to partnerships with international agricultural research centers. The most desired outputs from these include development and exchange of germplasm and assistance in capacity building and knowledge sharing. These findings confirm the anticipated constraints and needs over the next 10–20 years and affirm the importance of international agricultural research centers in providing support to address them.