Soil Mineral Stresses

1 Introduction: World Population and Agricultural Productivity.- 1.1 How Many People Are There?.- 1.2 Agricultural Requirements.- 1.2.1 Food Requirements.- 1.2.2 Food Supply.- 1.3 Population-Carrying Capacity.- 1.4 How Much Land Is There?.- 1.5 Increasing Food Production.- References.- 2 Conventional Plant Breeding for Tolerance to Problem Soils.- 2.1 Screening Techniques.- 2.2 Variability in Tolerance for Soil Stresses.- 2.2.1 Rice.- 2.3 Genetics of Tolerance for Soil Stresses.- 2.3.1 Gene Location and Linkages.- 2.3.2 Correlated Changes.- 2.4 Crop-Improvement.- 2.4.1 Introduction.- 2.4.2 Pure Line and Mass Selection.- 2.4.3 Hybridisation and Selection.- 2.4.3.1 Pedigree Method.- 2.4.3.2 Bulk Method.- 2.4.3.3 Backcross Breeding.- 2.4.3.4 Recurrent Selection.- 2.4.3.5 Rapid Generation Advance Procedures.- 2.4.4 Mutation Breeding.- 2.4.5 Polyploid Breeding.- 2.4.6 Heterosis Breeding.- 2.5 Summary.- References.- 3 Physiological Criteria in Screening and Breeding.- 3.1 Introduction.- 3.2 Reasons for the Use of Physiological Selection.- 3.2.1 The Complexity of Tolerance.- 3.2.2 Importing Tolerance from Wild Relatives.- 3.2.3 Measuring Stress Tolerance.- 3.2.4 Interaction Between Environmental Stresses.- 3.2.5 Limitations to the Use of Yield as a Selection Criterion.- 3.3 Salinity.- 3.3.1 Basic Problems.- 3.3.2 Salt Exclusion.- 3.3.3 Conditions Requiring Osmotic Adjustment.- 3.3.4 Characteristics Needed in Salt-Tolerant Plants.- 3.3.4.1 Control of Salt Uptake.- 3.3.4.2 Limiting the Damage That Excessive Ion Uptake Causes.- 3.3.4.3 Osmotic Adjustment.- 3.3.5 Agricultural Versus Ecological Advantage.- 3.3.6 Examples Where Knowledge of Physiological Mechanisms Would Aid Selection for Salt Tolerance.- 3.3.6.1 Where Tolerance Is Accidental.- 3.3.6.2 Where Tolerance Is Not a Single Character.- 3.3.6.3 Where Tolerance Is Incidental.- 3.3.6.4 Where a Mechanism Is As Important As Tolerance Itself.- 3.3.6.5 Where Screening/Selection Pressure Is Severe.- 3.4 Drought.- 3.4.1 Efficient Use of Water.- 3.4.2 Exploitation of Soil Moisture.- 3.4.3 Leaf Water Relations.- 3.4.4 Selection for Drought Tolerance.- 3.5 Physiological Selection Procedures.- 3.5.1 Advantages of Using Physiological Criteria.- 3.5.2 Constraints.- 3.5.3 Prospects.- References.- 4 Cytogenetic Manipulations in the Triticeae.- 4.1 Introduction.- 4.2 Background to Wheat and Salinity.- 4.3 Cytogenetics of Wheat.- 4.4 Transfer into Wheat of Alien Genes for Tolerance to Salt.- 4.5 The Development of Hybrids as New Crop Species.- 4.6 The Interface Between Cytogenetics and Physiology.- 4.7 Genetic Control of Salt Tolerance in Barley.- 4.8 Genes for Abiotic Stress Tolerance in the Triticeae.- 4.9 Examples of Alien Introduction.- 4.10 Genetic Markers in Plant Breeding.- 4.11 Summary.- References.- 5 Tissue Culture in the Improvement of Salt Tolerance in Plants.- 5.1 Introduction.- 5.2 Application of Tissue Culture to Obtain Salt-Tolerant Plants.- 5.2.1 Somatic Cell Selection.- 5.2.2 Parasexual Hybridisation.- 5.2.3 Gene Transformation.- 5.3 Tissue Culture in the Identification and Characterisation of Cellular Determinants of Salt Tolerance.- 5.3.1 Osmotic Adjustment Is a Fundamental Cellular Determinant of Salt Tolerance.- 5.3.2 Osmotic Adjustment Mediated by Ion Accumulation.- 5.3.3 Organic Osmotic Solute Accumulation in the Cytosol.- 5.3.3.1 Glycinebetaine Accumulation.- 5.3.3.2 Proline Accumulation.- 5.3.3.3 Accumulation of Other Organic Solutes.- 5.4 Conclusion.- References.- 6 The Agricultural Use of Native Plants on Problem Soils.- 6.1 Evolution of Domestic Species.- 6.2 Limits of Improving Existing Crops.- 6.2.1 Genetic Variability Within Crop Species.- 6.2.2 Salt Tolerance.- 6.2.3 Mineral Deficiency.- 6.2.4 Heavy Metal Toxicity.- 6.2.4.1 Extent of the Resource Base.- 6.2.4.2 Heavy Metal-Binding Proteins.- 6.3 Availability of Alternatives.- 6.4 Methods of Domestication.- 6.4.1 Extent of the Halophyte Resource Base.- 6.4.2 Use of Halophytes to Improve Rangeland Productivity.- 6.4.3 Use of Halophytes as Irrigated Crop Plants.- 6.4.3.1 Use of Forage Crops: Productivity.- 6.4.3.2 Potential for Use as Direct Food Crops.- 6.5 Time Scale for Agricultural Development.- 6.6 Conclusions.- References.- 7 Metal Toxicity.- 7.1 Introduction: Sources of Toxicity.- 7.2 The Measurement of Tolerance.- 7.2.1 Solution Culture Methods.- 7.2.2 Soil-Based Methods of Testing Tolerance.- 7.3 Variability in Wild Species.- 7.3.1 Tolerance to Heavy Metals.- 7.3.2 Tolerance of Aluminium and Manganese.- 7.4 Variability in Cultivated Species.- 7.4.1 Tolerance to Zinc.- 7.4.2 Tolerance to Aluminium and Manganese.- 7.4.2.1 Wheat.- 7.4.2.2 Sorghum.- 7.4.2.3 Rice.- 7.4.2.4 Maize.- 7.4.2.5 Other Species.- 7.5 The Genetic Basis of Metal Tolerance.- 7.5.1 Wild Species.- 7.5.2 Cultivated Species.- 7.6 The Physiological Basis of Tolerance to Metals.- 7.7 Synthesis.- References.- 8 Micronutrient Toxicities and Deficiencies in Rice.- 8.1 Introduction.- 8.2 Iron.- 8.2.1 Iron Deficiency.- 8.2.2 Iron Toxicity.- 8.3 Manganese.- 8.3.1 Manganese Deficiency.- 8.3.2 Manganese Toxicity.- 8.4 Zinc.- 8.4.1 Zinc Deficiency.- 8.5 Copper.- 8.5.1 Copper Deficiency.- 8.6 Boron.- 8.6.1 Boron Deficiency.- 8.6.2 Boron Toxicity.- 8.7 Molybdenum.- References.- 9 Summary: Breeding Plants for Problem Soils - Current Knowledge and Prospects.- 9.1 Why Grow Crops on Problem Soils?.- 9.2 Approaches to the Utilisation of Problem Soils.- 9.3 Selection of Parents and Within Breeding Populations.- 9.4 Tolerance and Potential Yield.- 9.5 Genetics of Tolerance to Problem Soils.- 9.6 Transfer from Other Species.- 9.7 Domestication of New Crops from the Native Flora.- 9.8 Outlook.