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.

Cloning and characterization of a putative GS3 ortholog involved in maize kernel development

Abstract: The GS3 gene was the first identified gene controlling the grain size in rice. It has been proven to be involved in the evolution of grain size during domestication. We isolated the maize ortholog, ZmGS3 and investigated its role in the evolution of maize grain size. ZmGS3 has five exons encoding a protein with 198 amino acids, and has domains in common with the rice GS3 protein. Compared with teosinte, maize has reduced nucleotide diversity at ZmGS3, and the reduction is comparable to that found in neutrally evolving maize genes. No positive selection was detected along the length of the gene using either the Hudson-Kreitman-Aguade or Tajima's D tests. Phylogenetic analysis reveals a distribution of maize sequences among two different clades, with one clade including related teosinte sequences. The nucleotide polymorphism analysis, selection test and phylogenetic analysis reveal that ZmGS3 has not been subjected to selection, and appears to be a neutrally evolving gene. In maize, ZmGS3 is primarily expressed in immature ears and kernels, implying a role in maize kernel development. Association mapping analysis revealed one polymorphism in the fifth exon that is significantly associated with kernel length in two environments. Also one polymorphism in the promoter region was found to affect hundred kernel weight in both environments. Collectively, these results imply that ZmGS3 is involved in maize kernel development but with different functional polymorphisms and thus, possibly different mechanisms from that of the rice GS3 gene.

Genome-wide association analysis reveals new targets for carotenoid biofortification in maize.

Abstract: Key message Genome-wide association analysis in CIMMYT’s association panel revealed new favorable native genomic variations in/nearby important genes such as hydroxylases and CCD1 that have potential for carotenoid biofortification in maize.

Timing of the Maternal-to-Zygotic Transition during Early Seed Development in Maize

Abstract: In animals, early embryonic development is largely dependent on maternal transcripts synthesized during gametogenesis. Recent data in plants also suggest maternal control over early seed development, but the actual timing of zygotic genome activation is unclear. Here, we analyzed the timing of the maternal-to-zygotic transition during early Zea mays seed development. We show that for 16 genes expressed during early seed development, only maternally inherited alleles are detected during 3 d after fertilization in both the embryo and the endosperm. Microarray analyses of precocious embryonic development in apomictic hybrids between maize and its wild relative, Tripsacum, demonstrate that early embryo development occurs without significant quantitative changes to the transcript population in the ovule before fertilization. Precocious embryo development is also correlated with a higher proportion of polyadenylated mRNA in the ovules. Our data suggest that the maternal-to-zygotic transition occurs several days after fertilization. By contrast, novel transcription accompanies early endosperm development, indicating that different mechanisms are involved in the initiation of endosperm and embryo development.

Combined use of δ13C, δ18O and δ15N tracks nitrogen metabolism and genotypic adaptation of durum wheat to salinity and water deficit

Abstract: Summary •Accurate phenotyping remains a bottleneck in breeding for salinity and drought resistance. Here the combined use of stable isotope compositions of carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) in dry matter is aimed at assessing genotypic responses of durum wheat under different combinations of these stresses. •Two tolerant and two susceptible genotypes to salinity were grown under five combinations of salinity and irrigation regimes. Plant biomass, δ13C, δ18O and δ15N, gas-exchange parameters, ion and N concentrations, and nitrate reductase (NR) and glutamine synthetase (GS) activities were measured. •Stresses significantly affected all traits studied. However, only δ13C, δ18O, δ15N, GS and NR activities, and N concentration allowed for clear differentiation between tolerant and susceptible genotypes. Further, a conceptual model explaining differences in biomass based on such traits was developed for each growing condition. •Differences in acclimation responses among durum wheat genotypes under different stress treatments were associated with δ13C. However, except for the most severe stress, δ13C did not have a direct (negative) relationship to biomass, being mediated through factors affecting δ18O or N metabolism. Based upon these results, the key role of N metabolism in durum wheat adaptation to salinity and water stress is highlighted.

Novel sources of resistance to Striga hermonthica in Tripsacum dactyloides, a wild relative of maize

Abstract: Summary • The parasitic weed Striga hermonthica lowers cereal yield in small-holder farms in Africa. Complete resistance in maize to S. hermonthica infection has not been identified. A valuable source of resistance to S. hermonthica may lie in the genetic potential of wild germplasm. • The susceptibility of a wild relative of maize, Tripsacum dactyloides and a Zea mays‐T. dactyloides hybrid to S. hermonthica infection was determined. Striga hermonthica development was arrested after attachment to T. dactyloides . Vascular continuity was established between parasite and host but there was poor primary haustorial tissue differentiation on T. dactyloides compared with Z. mays . Partial resistance was inherited in the hybrid. • Striga hermonthica attached to Z. mays was manipulated such that different secondary haustoria could attach to different hosts. Secondary haustoria formation was inhibited on T. dactyloides , moreover, subsequent haustoria formation on Z. mays was also impaired. • Results suggest that T. dactyloides produces a signal that inhibits haustorial development: this signal may be mobile within the parasite haustorial root system.