http://abe.ufl.edu/Faculty/jjones/ABE_5646/Xtra%20files/The%20DSSAT%20Cropping%20System%20Model.pdf

The DSSAT cropping system model

Drought tolerance improvement in crop plants: An integrated view from breeding to genomics

Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32-39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability.

/pdf/climate-variation-explains-a-third-of-global-crop-yield-49v478uhu9.pdf

Climate variation explains a third of global crop yield variability

Plant breeding and drought in C3 cereals: what should we breed for?

Seed dry weight response to source–sink manipulations in wheat, maize and soybean: a quantitative reappraisal

Contents About the Editors * Contributors * Preface * Part One: Wheat Physiology * Chapter 1. An Introduction to the Physiological-Ecological Analysis of Wheat Yield * Worldwide Importance of Wheat * A Niche for This Book * Objectives * Chapter 2. Wheat Development * Introduction * Dynamics of Initiation and Appearance of Vegetative and Reproductive Organs * Effects of Major Factors on the Duration of Developmental Phases * Chapter 3. Physiological and Numerical Components of Wheat Yield * Introduction * Factors Affecting Kernal Number * Factors Affecting Individual Kernal Weight * Summary and Strategies for Future Yield Improvement * Chapter 4. Nitrogen As Determinant of Wheat Growth and Yield * Introduction * Nitrogen in the Soil * Nitrogen Metabolism in the Plant * Nitrogen Effects at the Plant and Crop Level * Optimization of Nitrogen Fertilization * Water Supply and Nitrogen Assimilation * Chapter 5. Grain Quality and Its Physiological Determinants * Introduction * What Makes Wheat So Special?--The Wheat Proteins * The Nonprotein Components of the Wheat Grain * How Do Wheat Grains Grow? Grain Quality Is the Result of Interactions Between Grain Components * Conclusions * Part II: Wheat Ecology * Chapter 6. Effects of Sowing Date and the Determination of Optimum Sowing Date * Introduction * Sowing and Establishment * Growth and Development * Maturation and Harvest * Experimental Estimation of Optimum Sow Dates * Wheat in England * Wheat in Australia * Other Regions * Determination of Optimal Sowing Dates * Chapter 7. Plant Density and Distribution As Modifiers of Growth and Yield * Introduction * Ecophysiological Basis of Density Response * The Effect of Resources on Crop Density Response * The Effect of Sowing Date and Plant Arrangement * Mathematical Relationships Between Plant Yield and Density * Concluding Remarks * Chapter 8. Wheat Yield As Affected by Weeds * Introduction * Weeds of Wheat * Yield Losses * Competition * Justification for Weed Removal * Effects on Yield Components and Grain Quality * Phytotoxin Effects of Herbicides * Chapter 9. Wheat Growth, Yield, and Quality As Affected by Insect Herbivores * Introduction * Yield Responses to Herbivory * Functional Classification of Herbivores * Key Pests * Other Pests * Population-Level Responses to Herbivory * Concluding Remarks * Chapter 10. Wheat Yield As Affected by Disease * Introduction * Physiological Processes Interrupted by Wheat Pathogens * Diversion of Foodstuffs to Abnormal Uses (Bunt and Smuts) * Scab--An Exception * Chapter 11. Wheat As a Polyculture Component (Santiago J. Sarandon) * Introduction * How to Measure Intercropping Performance * Effect of Mixtures on Plant Diseases * Effect of Mixtures on Resource Use * Effect of Mixtures on Grain Quality * Intercropping Wheat with Other Species * The Evaluation of Genotypes for Intercropping * Future Research Needs * Concluding Remarks * Part III: Wheat Production Systems * Chapter 12. Wheat Production in the Great Plains of North America * Introduction * Description of Wheat Production Systems * Technological Factors That Have Increased Grain Yields in This Century * Transformation of Wheat Production Systems in the Future * Chapter 13. Wheat Cropping in Australia * Introduction * Wheat Climate and Soils * Historic Changes in Wheat Yield * Recent Changes in Wheat Yield * Current Situation of Wheat Farming * Challenges to Productivity Gain * Wheat Research and Extension * Future Perspectives * Chapter 14. Wheat Production in Mediterranean Environments * The Mediterranean Climate * Wheat in the Mediterranean Environments * Rotations * Germplasm * Concluding Remarks * Chapter 15. Wheat Production Systems of the Pampas * Introduction * Climate and Soils: Major Constraints for Wheat Production * Wheat Production Systems * Future Perspectives * Part IV: Breeding to Further Raise Wheat Yields * Chapter 16. Genetic Gains in Wheat Yield and Associated Physiological Changes During the Twentieth Century * Introduction * Plant Breeding and Genetic Gains in Grain Yield * Consequences of Breeding for Plant Height and Related Traits * Plant Breeding and Biomass: Effects on Partitioning and Growth * Genetic Improvements in Nitrogen and Phosphorus Economies * Numerical Yield Components in Old and Modern Cultivars * Conclusion * Chapter 17. Physiological Traits That Increase the Yield Potential of Wheat * Introduction * Identifying Promising Traits * Selecting for Promising Traits * Concluding Remarks * Chapter 18. Breeding Hybrid Wheat for Low-Yielding Environments * Introduction * Genotype-Stress Interaction * The Hybrid Profile * Genetic Diversity Is Paramount * Intrapopulation Improvement * Selection Within the Male Pool * Heterosis and Plant Population X Row Width Interactions * Hybrid Yield, Stability, and Response to Yield * The Ideal Hybrid * Chapter 19. Actual and Potential Contributions of Biotechnology to Wheat Breeding * Introduction * Molecular Markers, Maps, and Their Application * Introgression of "Alien" Genes into Wheat by Chromosome Engineering * Genetic Engineering of Wheat * Conclusion * Author Index * Subject Index * Reference Notes Included

Wheat: Ecology and Physiology of Yield Determination

In this chapter, the authors analyze the changes produced by breeders in wheat yield during just the last century, when scientific genetic improvement took place after the rediscovery of Mendel's laws The main objectives in writing the chapter were to identify the contributions of breeding to the improvement in wheat grain yield and the major physiological attributes that were modified with grain yield and grain protein as a result of the genetic improvement of wheat grain yield potential In this chapter, the authors have outlined most of these changes with the objective of summarizing those traits that could be useful in future breeding Austin et al and Slafer et al showed that genetic improvement in wheat grain yield has led to decreases in grain protein percentage Future breeding should exploit the genetic variability in physiological attributes to increase total biomass of the crop, maintaining present levels of partitioning between vegetative and reproductive tissues

Increases in grain yield in bread wheat from breeding and associated physiological changes

Genetic-improvement effects on pre-anthesis physiological attributes related to wheat grain-yield

Summary: Resume: Zusammenfassung

Two cultivars of each of three spring cereals (wheat, barley and oats) were grown with Avena fatua in a box experiment, where the effects of root and shoot competition were separated using soil and aerial partitions. Measures of resource complementarity (RYT) and of the relative severity of competition indicated that competition for soil resources, particularly nitrogen, was more severe than competition for aerial resources, i.e. light. When both root and shoot competition occurred, oats and barley were generally more competitive than wheat, but there were significant differences in competitive ability between cultivars of all three cereals. Although competition between cereals and A. fatua occurred predominantly below-ground, the various cultivars only differed slightly in root competitive ability against weeds. Nitrogen fertilizer did not significantly change the ranking of competitive abilities of the cultivars. Although shoot competition had less effect than root competition, the various cereals differed markedly in shoot competitive ability. The two oat cultivars, and the barley cultivar Egmont, had higher shoot competitive abilities than the two wheat cultivars or the barley cultivar Goldmarker. There was little evidence that differences in shoot competitive ability were due to differences in plant height.



Une comparaison de la competition racinaire et aerienne entre les cereales de printemps et Avena fatua L.



Deux cultivars de chacune des 3 cereales de printemps (ble, orge et avoine) ont ete cultives avec de l'Avena fatua dans des boites experimentales ou les effets de la competition aerienne et ceux de la competition racinaire etaient separees en utilisant des partitions de sol et d'air. Des mesures de complementarite de ressources (RYT) et de la severite relative de la competition ont montre que la competition pour les ressources du sol, en particulier l'azote, etait plus forte que la competition pour les ressources aeriennes comme la lumiere. Quand a fois on avait une competition aerienne et racinaire, l'avoine et l'orge etaient generalement plus competitives que le ble, mais il y avait des differences significatives dans l'aptitude a la competition entre les cullivars des 3 cereales. Bien que la competition enlre cereales et A. fatua soit apparue pour la majeure partie sous le sol, les differents cultivars ont seulement legerement differe dans leur aptitude a la competition contre les adventices. Les engrais azotes n'ont pas change de facon significative le niveau de la competitivite des cullivars. Bien que la competition aerienne soit moins forte que la racinaire, les differentes cereales ont exprime des differences nettes dans leur aptitude a la competition aerienne. Les 2 avoines et l'orge ‘Egmont’ ont une plus grande capacite de competition que les 2 bles et l'orge ‘Goldmaker’. II n'est pas ressorti que les differences dans la competitive aerienne soient liees a des differences de hauleur de plantes.



Konkurrenz im Wurzel- und im Sprosbereich zwischen Sommergetreide und Avena fatua L.



Je 2 Sorten von Sommerweizen, Sommergerste und Hafer wuchsen mit Avena fatua in einem Topfversuch, wo durch Trennwande die Wirkung der Wurzel- und der Sproskonkurrenz unterschieden werden konnte. Messungen der Nahrstoffaufnahme und der relativen Starke der Konkurrenz zeigten, das die Konkurrenz um Nahrstoffe im Boden, besonders Stickstoff, heftiger war als die Konkurrenz im Sprosbereich, z. B. um Licht. Lag sowohl Wurzel- wie Sproskonkurrenz vor, waren Hafer und Gerste allgemein konkurrenzstarker als Weizen, aber es gab bei allen 3 Getreidearten signifikante Unterschiede zwischen den Sorten. Obwohl die Konkurrenz zwischen den Getreiden und A. fatua vor allem im Wurzelbereich lag, unterschieden sich die verschiedenen Sorten da in ihrer Konkurrenzkraft nur wenig, was auch durch Stickstoffdungung nicht signifikant geandert werden konnte. Trotz der geringeren Bedeutung der Konkurrenz im Sprosbereich unterschieden sich die Getreidearten hier in ihrer Konkurrenzkraft deutlich: Die beiden Hafersorten und die Gerstensorte ‘Egmont’ubertrafen hierin die beiden Weizensorten oder die Gerstensorte ‘Goldmaker’. Es gab keine Hinweise darauf, das die Unterschiede der Konkurrenzkraft im Sprosbereich auf die Halmlange zuruckzufuhren sei.

A comparison of root and shoot competition between spring cereals and Avena fatua L.

Assessing the sustainability of complex development processes requires multi-causal and integrated analyses. We develop a system-based methodology, rooted in interdisciplinary discussion and consensus building between 15 experts, to construct a multi-causal diagram which examines the sustainability of the Argentine Pampas´ process of agriculturization. The resulting diagram includes 25 factors and provides a big-picture of the multiple dimensions and interrelations affecting sustainability. According to this examination, the increasing concentration of production and the incorporation of technological innovations, triggered by economic and institutional factors, are the cause of environmental distresses and social changes, whose consequences for sustainability are still highly disputed. Nevertheless, the symptoms of both environmental and social unsustainability are more evident in the case of the extra-Pampean regions than in the Pampas. This suggests that the Pampean agriculture model should not be transferred to these regions without substantial modifications. The experts did not reach consensus on whether the agriculturization process is overall sustainable or unsustainable. Lack of consensus revolved mainly around opposing perspectives regarding the significance of the threats to environmental sustainability. The magnitude of socio-distributive unbalance and loss of rural jobs were also contentious. Yet, the paper shows how the exercise of building a joint causal diagram was undoubtedly helpful for linking piece-meal disciplinary facts, brought in from all fronts, into a comprehensive and coherent picture.

Emilio H. Satorre

Papers

Wheat: Ecology and Physiology of Yield Determination

Increases in grain yield in bread wheat from breeding and associated physiological changes

Genetic-improvement effects on pre-anthesis physiological attributes related to wheat grain-yield

A comparison of root and shoot competition between spring cereals and Avena fatua L.

Multi-causal and integrated assessment of sustainability: the case of agriculturization in the Argentine Pampas