Disease Resistance In Plants

Disease Resistance in Plants, Second Edition, looks at genetic, epidemiologic, biochemical, and biometric principles for developing new cultivars possessing genetic resistance to diseases. It examines the nature of disease resistance and resistance genes, and it highlights the importance of stabilizing selection, sugar, biotrophy, and necrotrophy to obtain the greatest possible yields. Organized into 17 chapters, this volume begins with an overview of disease resistance in plants and the ways to develop disease-resistant variants. It then discusses unspecific resistance; the resistance gene paradox; susceptibility and resistance within narrow host taxa; phenotypic variation and gene numbers in host plants; discontinuous variation and cytoplasmic inheritance; and experimental difficulties in partitioning variance. The reader is also introduced to epistasis and the structure of virulence in pathogens; the notion of physiological race; how the pathogen adapts to the host; mutation in the pathogen from avirulence to virulence; horizontal and vertical resistance to disease and its epidemiological effects; and the link between protein polymorphism and vertical resistance. In addition, the book discusses genes for susceptibility in the host versus genes for avirulence (or virulence) in the pathogen; sink-induced loss of resistance; high-sugar disease processes and biotrophy; slow rusting of cereal crops; plant resistance against endemic disease; and the accumulation of resistance genes in heterogeneous host populations. This book will be useful to plant pathologists and plant breeders.

Plant resistance to pathogens is one of the most important strategies of disease control. Knowledge of resistance mechanisms, and of how to exploit them, has made a significant contribution to agricultural productivity. However, the continuous evolution of new variants of pathogen, ana additional control problems posed by new crops and agricultural methods, creates a need for a corresponding increase in our understanding of resistance and ability to utilize it. The study of resistance mechanisms also has attractions from a purely academic point of view. First there is the breadth of the problem, which can be approached at the genetical, molecular, cellular, whole plant or population lev~ls. Often there is the possibility of productive exchange of ideas between different disciplines. Then there is the fact that despite recent advances, many of the mechanisms involved have still to be fully elucidated. Finally, and compared with workers in other areas of biology, the student of resistance is twice blessed in having as his subject the interaction of two or more organisms, with the intriguing problems of recognition, specificity and co-evolution which this raises.

Induced or acquired resistance to disease in plants has been known for many years, but the phenomenon was studied in only a few laboratories until about a decade ago. Since then, there has been an increasing interest in induced resistance as a new, environmentally safe means of disease control, as well as a model for the study of the genes involved in host defence and the signals that control them. This increased interest led the editors of Induced Resistance to Disease in Plants to collect and summarise much of the current and older literature on the topic in a single volume. Each chapter covers its topic as comprehensively as possible, thus serving as a solid introduction to the literature, as well as expressing its writer's own views on the state of research in the area and giving an indication of where future research may lead. Induced Resistance to Disease in Plants addresses the biology of induced resistance in legumes, solanaceae, cucurbits and monocots, since these are the families that have received the most attention, followed by a discussion of the molecular basis of induced resistance, its genetic and evolutionary significance, and practical applications in disease control. The book will provide a background for those commencing work in the area, as well as a source of information for established workers who wish to learn about other areas of induced resistance.

Human population is escalating at an enormous pace and is estimated to reach 9.7 billion by 2050. As a result, there will be an increase in demand for agricultural production by 60–110% between the years 2005 and 2050 at the global level; the number will be even more drastic in the developing world. Pathogens, animals, and weeds are altogether responsible for between 20 to 40 % of global agricultural productivity decrease. As such, managing disease development in plants continues to be a major strategy to ensure adequate food supply for the world. Accordingly, both the public and private sectors are moving to harness the tools and paradigms that promise resistance against pests and diseases. While the next generation of disease resistance research is progressing, maximum disease resistance traits are expected to be polygenic in nature and controlled by selective genes positioned at putative quantitative trait loci (QTLs). It has also been realized that sources of resistance are generally found in wild relatives or cultivars of lesser agronomic significance. However, introgression of disease resistance traits into commercial crop varieties typically involves many generations of backcrossing to transmit a promising genotype. Molecular marker-assisted breeding (MAB) has been found to facilitate the pre-selection of traits even prior to their expression. To date, researchers have utilized disease resistance genes (R-genes) in different crops including cereals, pulses, and oilseeds and other economically important plants, to improve productivity. Interestingly, comparison of different R genes that empower plants to resist an array of pathogens has led to the realization that the proteins encoded by these genes have numerous features in common. The above observation therefore suggests that plants may have co-evolved signal transduction pathways to adopt resistance against a wide range of divergent pathogens. A better understanding of the molecular mechanisms necessary for pathogen identification and a thorough dissection of the cellular responses to biotic stresses will certainly open new vistas for sustainable crop disease management. This book summarizes the recent advances in molecular and genetic techniques that have been successfully applied to impart disease resistance for plants and crops. It integrates the contributions from plant scientists targeting disease resistance mechanisms using molecular, genetic, and genomic approaches. This collection therefore serves as a reference source for scientists, academicians and post graduate students interested in or are actively engaged in dissecting disease resistance in plants using advanced genetic tools.

Far from being passive elements in the landscape, plants have developed many sophisticated chemical and mechanical means of deterring organisms that seek to prey on them. This volume draws together research from ecology, evolution, agronomy, and plant pathology to produce an ecological genetics perspective on plant resistance in both natural and agricultural systems. By emphasizing the ecological and evolutionary basis of resistance, the book makes an important contribution to the study of how phytophages and plants coevolve. Plant Resistance to Herbivores and Pathogens not only reviews the literature pertaining to plant resistance from a number of traditionally separate fields but also examines significant questions that will drive future research. Among the topics explored are selection for resistance in plants and for virulence in phytophages; methods for studying natural variation in plant resistance; the factors that maintain intraspecific variation in resistance; and the ecological consequences of within-population genetic variation for herbivorous insects and fungal pathogens. "A comprehensive review of the theory and information on a large, rapidly growing, and important subject."—Douglas J. Futuyma, State University of New York, Stony Brook

From February 24 -28, 1992 an international symposium on Durability of Disease Resistance was held at the International Agricultural Centre in Wageningen, the Netherlands. The symposium, organized by the Department of Plant Breeding of Wageningen Agricultural University and the Centre for Plant Breeding and Repro duction Research, CPRO-DLO, was part of the DGIS funded programme Durable Resistance in Developing Countries. Without any form of prevention or protection nearly all crops will be seriously or even severely damaged by a range of pathogens. In modern agriculture man has been able to control many if not most pathogens using i) pesticides, ii) phyto sanitary methods such as control of seed and plant material in order to start a crop disease free, iii) agronomic measures such as crop rotation, iv) disease resis tance or combinations of these measures. Over the years the use of pesticides has increased enormously and so did the pro blems associated with pesticide use, such as environmental pollution and building of resistance and tolerance to these pesticides in the pathogens. The use of resis tance too increased strongly over the years and here too problems arose.