Cytogenetics of the Festuca-Lolium Complex

Contenu

1 The Festuca-Lolium Complex: a Fascinating Group of Grasses.- 1.1 Agronomic Importance.- 1.1.1 Association Between Fungal Infection and Agronomic Traits.- 1.2 Distribution.- 1.3 Genetic Systems and Strategy for Germplasm Collection and Preservation.- 1.3.1 Level of Hetero- or Homozygosity and Sampling.- 1.3.2 Preservation of Germplasm.- 2 Taxonomic Treatments.- 2.1 General Considerations.- 2.2 Taxonomic Value of Epidermal Patterns and Leaf Sections.- 2.3 Limitations Imposed by Natural Introgression.- 2.4 The Lolium-Festuca-Vulpia Complex.- 2.5 Lolium L.- 2.5.1 Salient Generic Features.- 2.5.2 The Outbreeding and Inbreeding Species.- 2.5.3 Crosses Between Outbreeders and Inbreeders: Possible Evolutionary Trends.- 2.5.4 Two Important Ryegrasses.- 2.5.5 Systematic Mutations and Their Taxonomic Implications.- 2.5.6 Vegetative Proliferation in Inflorescences: a Reproductive and Taxonomic Anomaly.- 2.6 Festuca L.- 2.6.1 Salient Generic Features.- 2.6.2 Classification into Sections.- 2.7 Festuca arundinacea, a Compilospecies.- 2.8 Cytotaxonomic Affinities: Phylogenetic Considerations in the Festuca-Vulpia-Lolium Complex.- 3 Karyotypes and Species Evolution and Divergence.- 3.1 Karyotypic Features and Taxonomy.- 3.2 General Techniques of Studying Somatic Chromosomes.- 3.2.1 Conventional Staining.- 3.2.2 General Karyotypic Features of Lolium Species.- 3.2.3 General Karyotypic Features of Festuca Species.- 3.2.4 Giemsa Staining.- 3.2.4.1 Lolium L.- 3.2.4.2 Festuca L.- 3.3 Chromosome Size Variation Among Diploids and Polyploids.- 3.4 Evolution by Increase in Chromosome Numbers.- 3.5 Evolution by Changes in DNA Content.- 3.5.1 Lolium L.- 3.5.2 Festuca L.- 3.6 DNA Content and Growth Habit.- 3.7 Constitutive Heterochromatin.- 3.8 Nucleolar Organizer Activity.- 4 Meiosis in Diploid and Polyploid Species.- 4.1 General Technique of Studying Meiosis.- 4.2 Meiosis in Diploids.- 4.3 Diploid-Like Meiosis in Polyploids.- 4.3.1 Genetic Control of Diploid-Like Meiosis and Disomic Inheritance in Hexaploid Tall Fescue.- 4.3.1.1 Meiotic Analysis of 10 x 10 Diallel: Chromosome Pairing in a Critical Monosomic.- 4.3.1.2 Disomic Inheritance.- 4.3.1.3 The Haplo-Insufficiency Hypothesis.- 4.3.2 Occurrence of Haplo-Insufficient Diploidizing Genes in Other Polyploids.- 4.3.3 Possible Dosage Effect of Diploidizing Gene(s).- 4.3.4 Can Tall Fescue Be Considered Autoallohexaploid?.- 4.3.5 Probable Location of the Diploidizing Gene(s) in Tall Fescue.- 4.4 Breakdown of Diploidizing Mechanism in Haploid Complements in Hybrids.- 4.4.1 Haplo-Insufficiency of Diploidizing Gene(s).- 4.4.2 Possible Effects of Parental Genotypes.- 4.5 Chromosome Pairing in Polyhaploids.- 4.6 B Chromosomes in Relation to Diploidization of Tall Fescue.- 4.7 Different Diploidizing Mechanisms Compared and Contrasted.- 5 Reproductive Isolation Barriers Within the Tall Fescue Complex.- 5.1 Cytogenetic Basis of Reproductive Isolation.- 5.1.1 Regular Meiosis.- 5.1.2 Irregular Meiosis with Multivalent Formation.- 5.1.3 Irregular Meiosis with Multivalents and Univalents.- 5.1.4 Irregular Meiosis with Univalents.- 5.2 Various Other Meiotic Abnormalities in Hybrids Between Diverse Ecotypes.- 5.3 Occurrence of Univalents at Metaphase I: a Case of Desynapsis.- 5.4 Formation of Multivalents: Genetic Bases.- 5.5 Haplo-Insufficiency of the Pairing Control Genes?.- 5.6 Genetic Repression of Diploidizing Gene(s): an Example.- 6 Phylogenetic and Breeding Implications of the Genetic Control of Chromosome Pairing.- 6.1 Phylogenetic Relationships.- 6.2 Evolutionary Implications.- 6.2.1 Introgression of Characters.- 6.2.2 Changes in Basic Chromosome Numbers.- 6.3 Breeding Implications.- 6.3.1 Estimation of Inbreeding in Tall Fescue.- 6.3.2 The Concept of "Chromosome Combining Ability" and Formulation of Breeding Programs.- 6.3.3 Use of Genetic Bridges.- 6.3.4 Breeding Dodecaploid Tall Fescue and Derivatives.- 6.3.5 Interspecific Gene Transfers.- 7 B Chromosomes.- 7.1 Occurrence and Adaptive Value.- 7.1.1 General Occurrence.- 7.1.2 B Chromosomes in Festuca pratensis Huds.: Adaptive Significance?.- 7.1.3 B Chromosomes in Lolium perenne L.- 7.2 Pairing Among B Chromosomes in Hexaploid Tall Fescue.- 7.3 Effect on Genetic Recombination.- 7.4 Suppression of Homoeologous Pairing in Hybrids.- 7.5 B Chromosomes in Relation to Plant Breeding.- 8 Natural and Induced Polyploidy.- 8.1 Natural Polyploidy and Its Adaptive Value in Festuca.- 8.2 Absence of Natural Polyploidy in Lolium.- 8.3 Induced Polyploidy in Lolium.- 8.3.1 Colchicine Treatment.- 8.3.2 Meiotic Doubling.- 8.4 Distinguishing Features of Synthetic Polyploids of Lolium.- 8.4.1 Morphological Features.- 8.4.2 Isozyme Patterns.- 8.4.3 Nucleolar Organizing Regions.- 8.4.4 Meiosis and Fertility.- 8.4.5 Ribulose 1, 5-Bisphosphate Carboxylase Activity.- 8.4.6 Colchicine-Induced Variation.- 8.5 Induced Polyploidy in Festuca.- 8.5.1 Tetraploid Meadow Fescue.- 8.5.2 Dodecaploid Tall Fescue.- 8.5.3 Synthesis of Triploid Hybrids Between F. pratensis and F. apennina [= F. pratensis var. apennina].- 8.6 Occurrence of Aneuploids in Synthetic Polyploids.- 8.6.1 Sources of Aneuploidy.- 8.6.2 Aneuploid Frequency.- 8.6.3 Undesirable Effects of Aneuploidy.- 8.7 Polyploidy in Relation to Plant Breeding.- 8.7.1 Importance of Cytological Diploidization in Improvement of Synthetic Polyploids.- 8.7.2 Polyploid Material of Breeding Value.- 9 Haploidy.- 9.1 Lolium Haploids.- 9.1.1 Anther Culture.- 9.1.2 Wide Hybridization.- 9.2 Festuca Haploids.- 9.2.1 Polyhaploids of Hexaploid Tall Fescue.- 9.2.2 Doubled Haploids of Tall Fescue.- 9.2.3 Chromosome Pairing in Polyhaploids.- 9.2.4 Polyhaploids of Decaploid Tall Fescue.- 10 Aneuploids.- 10.1 Lolium.- 10.1.1 Isolation of Trisomics.- 10.1.2 Meiosis in Trisomics.- 10.1.3 Location of Genes.- 10.2 Hexaploid Tall Fescue.- 10.2.1 Isolation of Monosomics and a Nullisomic.- 10.2.2 Trisomics.- 10.2.3 Future Work.- 11 Intra- and Inter-Specific Hybridization, Genome Relationships, and Plant Improvement.- 11.1 General Importance.- 11.2 Crossing Techniques.- 11.2.1 Choice of Parents.- 11.2.2 Hybridization.- 11.3 The Embryo Rescue Technique.- 11.4 Extensive Hybridization Work.- 11.5 General Meiotic Abnormalities in Wide Hybrids.- 11.6 Phylogenetic Proximity Among Species of the Lolium-Festuca Complex: a Generalized Picture.- 11.7 Intraspecific Hybrids in Lolium L.- 11.7.1 Cytoplasmic Male Sterility.- 11.7.2 Diploid x Tetraploid Crosses.- 11.8 Intraspecific Hybrids in Festuca L..- 11.8.1 Inter-Ecotype Hybrids.- 11.8.2 Hybrids Between Material at Different Ploidy Levels.- 11.9 Interspecific Hybrids in Lolium.- 11.9.1 General Genome Relationships.- 11.9.1.1 Intragroup and Intergroup Crosses.- 11.9.1.2 Do Lolium Species Have the Same Basic Genome?.- 11.10 Hybrids Between the Two Ryegrasses: Development of Superior Germplasm.- 11.10.1 Diploid Hybrids.- 11.10.2 Tetraploid Hybrids.- 11.10.3 Preferential Pairing Between Lp-Lp and Lm-Lm Chromosomes.- 11.10.4 Cytological Diploidization of Tetraploid Hybrids.- 11.10.5 Agronomically Useful LmLm LpLp Hybrids.- 11.10.6 Recombination of Traits via a Triploid Hybrid.- 11.11 Interspecific Hybrids in Festuca.- 11.11.1 F. pratensis (2x) x F. arundinacea (6x).- 11.11.2 F. pratensis (2x) x F. glaucescens (4x).- 11.11.3 F. pratensis (2x) x F. mairei (4x).- 11.11.4 F. pratensis (2x) x F. apennina De Not. (4x).- 11.11.5 F. arundinacea (6x, 8x, 10x) x F. mairei (4x).- 11.11.6 F. glaucescens (4x) x F. mairei (4x).- 11.11.7 Chromosome Pairing Relationships Among Diploid Species of Festuca.- 11.11.8 General Conclusions on Genome Relationships Among Species of Festuca.- 11.12 F. arundinacea (6x) x F. gigantea (6x) Hybridization: Development of Superior Germplasm.- 11.12.1 Chromosome Relationships.- 11.12.2 Material of Breeding Value.- 12 Intergeneric Hybridization, Genome Relationships, and Plant Improvement.- 12.1 Possible Affinity Between Festuca and Other Grass Genera.- 12.2 General Affinities Between Lolium and Festuca.- 12.3 Natural H…