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.

Genetic Diversity Determined within and among CIMMYT Maize Populations of Tropical, Subtropical, and Temperate Germplasm by SSR Markers

Abstract: Genetic diversity in maize (Zea mays L.) plays a key role for future breeding progress. The main objectives of our study were to (i) investigate the genetic diversity within and among CIMMYT maize populations by simple sequence repeat (SSR) markers, (ii) examine genotype frequencies for deviations from Hardy-Weinberg equilibrium (HWE) at individual loci, and (iii) test for linkage disequilibrium (LD) between pairs of loci. Twenty-three maize populations and pools established in 1974, which mostly comprise germplasm from different racial complexes adapted to tropical, subtropical intermediate-maturity, subtropical early-maturity, and temperate megaenvironments (ME), were fingerprinted by 83 SSR markers covering the entire maize genome. Across all populations, 27% of the SSR markers deviated significantly from HWE with an excess of homozygosity in 99% of the cases. We observed no evidence for genome-wide LD among pairs of loci within each of the seven tropical populations analyzed. Estimates of genetic differentiation (G ST) between populations within MEs averaged 0.09 and revealed that most of the molecular variation was found within the populations. Principal coordinate analysis based on allele frequencies of the populations revealed that populations adapted to the same ME clustered together and, thus, supported clearly the ME structure.

Large-Scale Development of Cost-Effective Single-Nucleotide Polymorphism Marker Assays for Genetic Mapping in Pigeonpea and Comparative Mapping in Legumes

Abstract: Single-nucleotide polymorphisms (SNPs, >2000) were discovered by using RNA-seq and allele-specific sequencingapproachesinpigeonpea(Cajanuscajan).FormakingtheSNPgenotypingcost-effective,successful competitive allele-specific polymerase chain reaction (KASPar) assays were developed for 1616 SNPs and referredtoasPKAMs(pigeonpeaKASParassaymarkers).ScreeningofPKAMson24genotypes[23fromcultivated species and 1 wild species (Cajanus scarabaeoides)] defined a set of 1154 polymorphic markers (77.4%) with a polymorphism information content (PIC) value from 0.04 to 0.38. One thousand and ninety-four PKAMs showed polymorphisms between parental lines of the reference mapping population (C. cajan ICP 28 3 C. scarabaeoides ICPW 94). By using high-quality marker genotyping data on 167 F2 lines from the population, a comprehensive genetic map comprising 875 PKAMs with an average intermarker distance of 1.11 cM was developed. Previously mapped 35 simple sequence repeat markers were integrated into the PKAM map and an integrated genetic map of 996.21 cM was constructed. Mapped PKAMs showed a higher degree of synteny with the genome of Glycine max followed by Medicago truncatula and Lotus japonicus and least with Vigna unguiculata. These PKAMs will be useful for genetics research and breeding applications in pigeonpea and for utilizing genome information from other legume species.

Grouping of accessions of Mexican races of maize revisited with SSR markers

Abstract: Mexican races of maize (Zea mays L.) represent a valuable genetic resource for breeding and genetic surveys. We applied simple sequence repeat (SSR) markers to characterize 25 accessions of races of maize from Mexico. Our objectives were to (1) study the molecular genetic diversity within and among these accessions and (2) examine their relationships as assumed previously on the basis of morphological data. A total of 497 individuals were fingerprinted with 25 SSR markers. We observed a high total number of alleles (7.84 alleles per locus) and total gene diversity (0.61), confirming the broad genetic base of the maize races from Mexico. In addition, the accessions were grouped into distinct racial complexes on the basis of a model-based clustering approach. The principal coordinate analyses of the four Modern Incipient hybrids corroborated the proposed parental races of Chalqueno, Conico Norteno, Celaya, and Bolita on the basis of the morphological data. Consequently, for some of the accessions, hybridizations provide a clue that can further be used to explain the associations among the Mexican races of maize.