Inheritance and linkage study of isozyme loci and morphological traits in red clover
Information on inheritance of isozymes and linkage maps in Trifolium pratense L is limited. Genetic analysis of 18 isozyme systems and three morphological traits (white vs. pink flower, present vs. absent leaf marker and green vs. sun-red stem) was conducted. Six loci of four isozymes had simple Mendelian inheritance. Joint segregation analyses among 8 isozyme loci and 3 morphological gene markers (55 pair-wise combinations) resulted in the assignment of one linkage group. Two morphological markers coding for flower (c) and stem (gs) color were found to be in the same linkage group based on the analyses of two segregating families. The recombination values of the two progenies for c-gs were 0.079 and 0.113. No linkage was found between any of the isozyme loci and the morphological traits.
Molecular marker-facilitated investigations of quantitative trait loci in maize. II. Factors influencing yield and its component traits
Because traits such as grain yield are polygenically inherited and strongly influenced by environment, determination of genotypic values from phenotypic expression is not precise and improvement strategies are frequently based on low heritabilities. Increased knowledge of the genetic factors involved in the expression of yield should enhance the improvement of this trait. The objectives of this study were to identify and locate genetic factors (i.e., quantitative trait loci, QTL's) associated with grain yield and 24 yield-related traits in two F, populations of maize (Zea mays L.) using isozyme marker loci. (The populations were generated by selfing the F, hybrids CO159 X Tx303 and T232 X CM37.) In addition, assessments of the types and magnitudes of gene effects expressed by these QTL's were made. About two-thirds of the associations among 17 to 20 marker loci and the 25 quantitative traits were significant with a large proportion of these at P < 0.001. Proportions of variation accounted for by genetic factors associated with individual marker loci varied from less than 1% to more than 11%. Although individual marker loci accounted for relatively small proportions of the phenotypic variation for these yield-related traits, differences between mean phenotypic values of the two homozygous classes at certain loci were occasionally more than 16% of the population mean. Also, different genomic regions contributed to yield through different subsets of the yield-related traits. Predominant types of gene action varied among loci and among the 25 quantitative traits. For plant grain yield, top ear grain weight, and ear length, the gene action was primarily dominant or overdominant. However, mainly additive gene action was implicated for ear number, kernel row number, and second ear grain weight. Results from these studies should prove to be useful for manipulating QTL's in marker-facilitated selection programs. Additional index words: Quantitative genetics, Grain yield, Zea mays L., Gene action, Genetic factors, Genetic variation, Marker loci associations. I MAIZE (Zea mays L.) and other plant species, the genetic bases of quantitative traits, such as yield and most of its component traits, are normally assumed to be polygenic in nature largely because the phenotypic expressions of these traits form continuous distributions. Typically, estimates of genotypic effects associated with these traits are expressed as an average value across the genome. With the development of molecular markers (isozymes, and, more recently, restriction fragment length polymorphisms, RFLP's), the capabilities are now available for discriminating individual gene effects. Thus, numbers and genomic distribution of genetic factors (quantitative trait loci, QTL's) involved in the expression of yield and other quantitatively inherited traits can now be elucidated. Molecular marker techniques also provide the means for investigating the types and magnitudes of gene effects attributed to these QTL's. The theoretical basis for interpreting the association of marker loci with QTL's has been outlined by Mather and Jinks (1971), Tanksley, et al. (1982), Seller and Beckmann (1983), and Edwards et al. (1987). The theory exploits the fact that the marker locus serves to identify, or "mark", the chromosomal region in its vicinity and enables that region to be followed in inheritance studies. Alternative homologous chromosomal regions characterized by alternative alleles at the marker locus can be replicated extensively in different individuals and compared for quantitative trait effects, while other chromosomal regions in the same individuals and the environmental factors affecting them are permitted to vary at random. If adequate markers are available and are distributed appropriately throughout the genome, it is possible to evaluate all chromosomal regions for their effects on numerous quantitative traits of interest. A high level of linkage disequilibrium between the marker loci and QTL's is an essential feature of the approach. Earlier studies to examine the association of specific isozyme loci with grain yield in maize involved monitoring allelic frequency changes at a large number of enzyme loci in different cycles of recurrent selection experiments. In several long-term recurrent selection experiments in North Carolina, allelic frequencies at 1 Joint contribution from the USDA-ARS and the North Carolina ARS, North Carolina State Univ., Raleigh, NC. This investigation was supported in part by USDA Competitive Research Grant 83CRCR-1-1273 and in pan by Natl. Inst. of Health Res. Grant no. GM 11546 from the Natl. Inst. of General Medical Sciences of the USA. Paper no. 10644 of the Journal Series of the North Carolina ARS, Raleigh, NC. Received 11 Aug. 1986. 2 Research geneticist, USDA-ARS, and professor of genetics, North Carolina State Univ., Raleigh, NC 27695-7614; geneticist, USDAARS (now with Pillsbury Company, LeSueur, MN); and assistant professor of botany, Iowa State Univ., Ames, IA 50011. Published in Crop Sci. 27:639-648 (1987). Published July, 1987
France in the Middle Ages 987-1460 : from Hugh Capet to Joan of Arc
Translatora s Note. Foreword. List of Illustrations. List of Genealogical Tables. Part I: The Inheritance: . 1. The Empire. 2. The Frankish People. 3. The Principalities. 4. Disturbances. Part II: Lordship:. 5. The Village. 6. The Castle. 7. The Church. 8. King and Lord. Part III: Origins of State and Nation:. 9. The Great Age of Progress. 10. Louis VII. 11. Philip Augustus. 12. The South. 13. The Thirteenth Century. 14. The Fourteenth Century. 15. The Maid of Orleans. Epilogue. Chronology. Bibliography. Index.