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.

Progress in breeding wheat for yield and adaptation in global drought affected environments

Abstract: The impact of wheat (Triticum aestivum L.) germplasm from the International Maize and Wheat Improvement Center (CIMMYT) in the highly productive environments of the developing world has been significant. However, 55% of the area sown to wheat in these countries is periodically affected by drought and the impact of CIMMYT germplasm on productivity in these areas is not dear. Our objective was to measure rates of yield improvement for the period 1979 through 1998 using yield data from CIMMYT's Elite Spring Wheat Trial (ESWYT) and Semi-Arid Wheat Yield Trial (SAWYT). The mean yield of the five highest yielding entries from each site was expressed as a percent of the trial mean (%TM). The trial mean yield (TM) and the mean yield of locally adapted check cultivars (LC) were used to provide estimates of the productivity of each environment. Measuring rates of progress by means of %TM, TM, and LC were favored to the use of mean yield alone as variable annual rainfall and subsequent fluctuations in productivity influence yield in dry environments. Yearly rates of progress were determined by measuring change in %TM and change in TM. In environments yielding less than 4 Mg ha -1 the respective increases in %TM and TM for SAWYT were 4.38 and 0.09% yr -1 . The equivalent rates for ESWYT were 0.34 and 0.19% yr -1 . In environments yielding 4 Mg ha -1 or more the respective rates of progress in %TM and TM for SAWYT were 0.85 and 2.87% yr -1 compared with 0.26 and 0.494% yr -1 observed in the ESWYT. Comparisons of %TM, TM, and LC for representative locations in Mexico, Argentina, Syria, and Portugal demonstrated progress in %TM ranging from highly significant to stable, regardless of local fluctuations in productivity.

Relationship, evolutionary fate and function of two maize co-orthologs of rice GW2 associated with kernel size and weight.

Abstract: Background: In rice, the GW2 gene, found on chromosome 2, controls grain width and weight. Two homologs of this gene, ZmGW2-CHR4 and ZmGW2-CHR5, have been found in maize. In this study, we investigated the relationship, evolutionary fate and putative function of these two maize genes. Results: The two genes are located on duplicated maize chromosomal regions that show co-orthologous relationships with the rice region containing GW2. ZmGW2-CHR5 is more closely related to the sorghum counterpart than to ZmGW2-CHR4. Sequence comparisons between the two genes in eight diverse maize inbred lines revealed that the functional protein domain of both genes is completely conserved, with no nonsynonymous polymorphisms identified. This suggests that both genes may have conserved functions, a hypothesis that was further confirmed through linkage, association, and expression analyses. Linkage analysis showed that ZmGW2-CHR4 is located within a consistent quantitative trait locus (QTL) for one-hundred kernel weight (HKW). Association analysis with a diverse panel of 121 maize inbred lines identified one single nucleotide polymorphism (SNP) in the promoter region of ZmGW2-CHR4 that was significantly associated with kernel width (KW) and HKW across all three field experiments examined in this study. SNPs or insertion/deletion polymorphisms (InDels) in other regions of ZmGW2-CHR4 and ZmGW2-CHR5 were also found to be significantly associated with at least one of the four yield-related traits (kernel length (KL), kernel thickness (KT), KW and HKW). None of the polymorphisms in either maize gene are similar to each other or to the 1 bp InDel causing phenotypic variation in rice. Expression levels of both maize genes vary over ear and kernel developmental stages, and the expression level of ZmGW2CHR4 is significantly negatively correlated with KW. Conclusions: The sequence, linkage, association and expression analyses collectively showed that the two maize genes represent chromosomal duplicates, both of which function to control some of the phenotypic variation for kernel size and weight in maize, as does their counterpart in rice. However, the different polymorphisms identified in the two maize genes and in the rice gene indicate that they may cause phenotypic variation through different mechanisms.

The Plant Ontology as a Tool for Comparative Plant Anatomy and Genomic Analyses

Abstract: The Plant Ontology (PO; http://www.plantontology.org/) is a publicly available, collaborative effort to develop and maintain a controlled, structured vocabulary (‘ontology’) of terms to describe plant anatomy, morphology and the stages of plant development. The goals of the PO are to link (annotate) gene expression and phenotype data to plant structures and stages of plant development, using the data model adopted by the Gene Ontology. From its original design covering only rice, maize and Arabidopsis, the scope of the PO has been expanded to include all green plants. The PO was the first multispecies anatomy ontology developed for the annotation of genes and phenotypes. Also, to our knowledge, it was one of the first biological ontologies that provides translations (via synonyms) in non-English languages such as Japanese and Spanish. As of Release #18 (July 2012), there are about 2.2 million annotations linking PO terms to >110,000 unique data objects representing genes or gene models, proteins, RNAs, germplasm and quantitative trait loci (QTLs) from 22 plant species. In this paper, we focus on the plant anatomical entity branch of the PO, describing the organizing principles, resources available to users and examples of how the PO is integrated into other plant genomics databases and web portals. We also provide two examples of comparative analyses, demonstrating how the ontology structure and PO-annotated data can be used to discover the patterns of expression of the LEAFY (LFY) and terpene synthase (TPS) gene homologs.

Calibrating the leaf color chart for nitrogen management in different genotypes of rice and wheat in a systems perspective

Abstract: Low N use efficiency (NUE) continues to be a problem in the rice (Oryza saliva L.)-wheat (Triticum aestivum L.) cropping system. The leaf color chart (LCC)-based real-time N management can be used to optimize/synchronize N application with crop demand or to improve existing fixed split N recommendations. We conducted a field experiment during 2001-2003 at Modipuram, India, to determine the threshold LCC values for N application in rice and wheat, assess the need for basal N application, calibrate the LCC with a chlorophyll meter (SPAD), and work out the economics of rice-wheat systems. Treatments consisted of LCC scores of 2 to 5 for different cultivars of rice and wheat and were compared with the zero-N control and a recommended fixed-time N splitting. In rice, LCC ≤ 3 for 'Basmati-370', 4 for 'Saket-4', and 5 for 'Hybrid 6111/PHB-71' produced higher yield and NUE than recommended N splits. In wheat, maintenance of LCC ≤ 4 required 120 kg N ha -1 , which produced higher grain yield, N uptake, and NUE than that of recommended N splits. Chlorophyll meter reading and crop growth rate (g m -2 day -1 ') at 15 d after transplanting in rice and 21 d after seeding in wheat were not significantly different with or without basal N application, indicating that basal N application in rice and wheat was not necessary in soils having relatively high indigenous N supply. Both LCC and SPAD readings (r = 0.84 to 0.91) were highly correlated in rice and wheat. Net returns were 19 to 31% higher in LCC-based N management than in fixed-time N application for rice-wheat cropping.