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.

Metabolite profiles of maize leaves in drought, heat and combined stress field trials reveal the relationship between metabolism and grain yield

Abstract: The development of abiotic stress-resistant cultivars is of premium importance for the agriculture of developing countries. Further progress in maize (Zea mays) performance under stresses is expected by combining marker-assisted breeding with metabolite markers. In order to dissect metabolic responses and to identify promising metabolite marker candidates, metabolite profiles of maize leaves were analyzed and compared with grain yield in field trials. Plants were grown under well-watered conditions (control) or exposed to drought, heat, and both stresses simultaneously. Trials were conducted in 2010 and 2011 using 10 tropical hybrids selected to exhibit diverse abiotic stress tolerance. Drought stress evoked the accumulation of many amino acids, including isoleucine, valine, threonine, and 4-aminobutanoate, which has been commonly reported in both field and greenhouse experiments in many plant species. Two photorespiratory amino acids, glycine and serine, and myoinositol also accumulated under drought. The combination of drought and heat evoked relatively few specific responses, and most of the metabolic changes were predictable from the sum of the responses to individual stresses. Statistical analysis revealed significant correlation between levels of glycine and myoinositol and grain yield under drought. Levels of myoinositol in control conditions were also related to grain yield under drought. Furthermore, multiple linear regression models very well explained the variation of grain yield via the combination of several metabolites. These results indicate the importance of photorespiration and raffinose family oligosaccharide metabolism in grain yield under drought and suggest single or multiple metabolites as potential metabolic markers for the breeding of abiotic stress-tolerant maize.

Relative impacts of tillage, residue management and crop-rotation on soil bacterial communities in a semi-arid agroecosystem

Abstract: In this study, the effect of limited tillage versus traditional tillage, residue retention versus removal and crop rotation (maize–wheat) versus monoculture (maize) on the bacterial community structure in soils was investigated by means of 454 pyrosequencing of the 16S rRNA gene. Using taxonomic and phylogenetic information it was found that zero tillage most affected the bacterial communities. The relative abundance of Actinobacteria, Betapreoteobacteria and Gammaproteobacteria was affected by tillage and correlated to the total organic carbon (TOC) and clay content in soil. Residue management had a significant effect on the bacterial community structure when phylogenetic membership and the total enumeration of bacteria were considered. Residue management affected the relative abundance of Bacteroidetes, Betaproteobacteria, Cyanobacteria and Gemmatimonadetes. When no tillage was applied, crop residue management affected the microbial communities more than when conventional tillage was applied. Wheat–maize rotation or crop monoculture did not affect the bacterial community structure. No significant differences in richness, diversity and total abundance of bacteria was found between the treatments. This indicated that even though phylotypes changed, the number and diversity of the bacterial communities were similar.

The Potential for Increasing the Iron and Zinc Density of Maize through Plant-breeding:

Abstract: The Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT) maize-breeding programme has been focusing on identifying white-grained maize germplasm that has the potential to increase kernel i...

Genetic Characterization of CIMMYT Inbred Maize Lines and Open Pollinated Populations Using Large Scale Fingerprinting Methods

Abstract: The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 samples of maize (Zea mays L.) and teosinte (Z. mays, several subspecies), a wild relative of maize. Seven CIMMYT populations and 57 inbreds were characterized by simple sequence repeat (SSR) markers. SSRs chosen from almost every bin in the maize genetic map were tested for repeatability, ease of automation in allele calling, and discrimination (information content). Eighty-five SSRs were found to be repeatable and easily automated, and were run on all material in the study. Fifty-three of these SSRs were found to be the most discriminatory and will be used in future routine fingerprinting studies. The seven breeding populations clustered as would be predicted on the basis of pedigree and heterotic grouping. Genetic diversity within each population was significantly higher than diversity between populations, indicating that the populations are heterogeneous at the molecular level. The inbreds also showed a high level of genetic diversity, indicating that CIMMYT breeders have successfully incorporated considerable genetic diversity into CIMMYT maize germplasm. Only lines closely related by pedigree clustered together. Population of origin and heterotic grouping were not assodated with the clusters formed on the basis of SSR markers, a result consistent with the high level of diversity within source populations of the inbreds. Although this will make it more difficult to assign CIMMYT inbred lines to currently existing heterotic groups by means of markers, the markers may be useful in refining the CIMMYT heterotic groups into additional and more uniform groups.

Low-P tolerance by maize (Zea mays L.) genotypes: Significance of root growth, and organic acids and acid phosphatase root exudation

Abstract: We investigated some mechanisms, which allow maize genotypes to adapt to soils which are low in available P. Dry matter production, root/shoot-ratio, root length and root exudation of organic acids and acid phosphatase were investigated in four maize genotypes grown under P-deficient and P-sufficient conditions in sterile hydroponic culture. A low-P tolerant, an acid-tolerant and a low-P susceptible genotype of maize were compared with a Swiss commercial cultivar. The study found increased root development and increased exudation of acid phosphatase under P-deficient conditions in all maize genotypes, except for the Swiss cultivar. Effects on root formation and acid phosphatase were greater for the low-P tolerant than for the low-P susceptible, and the acid soil tolerant genotypes. Organic acid contents in root tissues were increased under P deficiency and related to increased PEPC activity. However, the increase in contents was associated with an increase in exudation for the low-P tolerant genotype only. The low-P susceptible genotype was characterized by high organic acid content in roots and low organic acid exudation. The organic acids content in the phloem exudates of shoots was related to root exudation under different P supply, to the difference between lines in organic acids root content, but not to the low-P tolerance or susceptibility of maize genotypes.