Molecular Biology In Plant Pathogenesis And Disease Management

Investigations on various aspects of plant-pathogen interactions have the ultimate aim of providing information that may be useful for the development of effective crop disease management systems. Molecular techniques have accelerated the formulation of short- and long-term strategies of disease management. Exclusion and eradication of plant pathogens by rapid and precise detection and identification of microbial pathogens in symptomatic and asymptomatic plants and planting materials by employing molecular methods has been practiced extensively by quarantines and certification programs with a decisive advantage. Identification of sources of resistance genes, cloning and characterization of desired resistance genes and incorporation of resistance gene(s) into cultivars and transformation of plants with selected gene(s) have been successfully performed by applying appropriate molecular techniques. Induction of resistance in susceptible cultivars by using biotic and abiotic inducers of resistance is a practical proposition for several crops whose resistance levels could not be improved by breeding or transformation procedures. The risks of emergence of pathogen strains less sensitive or resistant to chemicals have been reduced appreciably by rapid identification of resistant strains and monitoring the occurrence of such strains in different geographical locations.

Studies on molecular biology of pathogens, infection process and disease resistance, have provided information essentially required to understand the vulnerable stages at which the pathogens can be tackled effectively and to adopt novel strategies to incorporate disease resistance genes from diverse sources and /or to induce resistance of cultivars with desirable agronomic attributes using biotic or abiotic agents. The nature of interaction between the gene products of the pathogen and plant appears to determine the outcome of the interaction resulting in either disease progression or suppression. Transgenic plants with engineered genes show promise for effective exploitation of this approach for practical application. Research efforts during the recent years to sequence the whole genomes of the pathogens and plants may lead to development of better ways of manipulating disease resistance mechanisms enabling the grower to achieve higher production levels and the consumer to enjoy safer food and agricultural products. Experimental protocols included in appropriate chapters will be useful for researchers and graduate students.

Investigations on various aspects of plant-pathogen interactions have the ultimate aim of providing information that may be useful for the development of effective crop disease management systems. Molecular techniques have accelerated the formulation of short- and long-term strategies of disease management. Exclusion and eradication of plant pathogens by rapid and precise detection and identification of microbial pathogens in symptomatic and asymptomatic plants and planting materials by employing molecular methods has been practiced extensively by quarantines and certification programs with a decisive advantage. Identification of sources of resistance genes, cloning and characterization of desired resistance genes and incorporation of resistance gene(s) into cultivars and transformation of plants with selected gene(s) have been successfully performed by applying appropriate molecular techniques. Induction of resistance in susceptible cultivars by using biotic and abiotic inducers of resistance is a practical proposition for several crops whose resistance levels could not be improved by breeding or transformation procedures. The risks of emergence of pathogen strains less sensitive or resistant to chemicals have been reduced appreciably by rapid identification of resistant strains and monitoring the occurrence of such strains in different geographical locations.

Studies on the phenomenon of plant pathogenesis (disease development) have been useful to have a deep insight into the interactions between host plant and the pathogen. Depending on the levels of susceptibility (compatibility) or resistance (incompatibility) of the host plant and virulence of the pathogen, disease development may progress, either leading to symptom expression or result in the suppression of pathogen proliferation. Molecular techniques have been applied to elucidate the nature of interactions between the gene products of the plant and pathogen at cellular and molecular levels. Successful evasion of host’s surveillance system and subsequent activities of metabolites of the pathogen (enzymes and toxins) encoded by pathogen genes counteracting the effects of various defense-related antimicrobial compounds present already or produced by the host plants, after initiation of infection have been critically studied by applying various molecular techniques. In addition to studying various phases of disease development in individual plants, molecular methods have been demonstrated to be effective, in gathering data on various aspects of epidemiology under natural conditions where the interaction of pathogen with populations of plants is influenced significantly by the environmental conditions existing in different ecosystems. This volume focuses on the possibility of applying the knowledge on pathogenesis and molecular epidemiology to determine the vulnerable stages in the life cycles of the pathogens that can be disrupted to achieve more effective disease control.

Studies on molecular biology of pathogens, infection process and disease resistance, have provided information essentially required to understand the vulnerable stages at which the pathogens can be tackled effectively and to adopt novel strategies to incorporate disease resistance genes from diverse sources and /or to induce resistance of cultivars with desirable agronomic attributes using biotic or abiotic agents. The nature of interaction between the gene products of the pathogen and plant appears to determine the outcome of the interaction resulting in either disease progression or suppression. Transgenic plants with engineered genes show promise for effective exploitation of this approach for practical application. Research efforts during the recent years to sequence the whole genomes of the pathogens and plants may lead to development of better ways of manipulating disease resistance mechanisms enabling the grower to achieve higher production levels and the consumer to enjoy safer food and agricultural products. Experimental protocols included in appropriate chapters will be useful for researchers and graduate students.

Studies on the phenomenon of plant pathogenesis (disease development) have been useful to have a deep insight into the interactions between host plant and the pathogen. Depending on the levels of susceptibility (compatibility) or resistance (incompatibility) of the host plant and virulence of the pathogen, disease development may progress, either leading to symptom expression or result in the suppression of pathogen proliferation. Molecular techniques have been applied to elucidate the nature of interactions between the gene products of the plant and pathogen at cellular and molecular levels. Successful evasion of host’s surveillance system and subsequent activities of metabolites of the pathogen (enzymes and toxins) encoded by pathogen genes counteracting the effects of various defense-related antimicrobial compounds present already or produced by the host plants, after initiation of infection have been critically studied by applying various molecular techniques. In addition to studying various phases of disease development in individual plants, molecular methods have been demonstrated to be effective, in gathering data on various aspects of epidemiology under natural conditions where the interaction of pathogen with populations of plants is influenced significantly by the environmental conditions existing in different ecosystems. This volume focuses on the possibility of applying the knowledge on pathogenesis and molecular epidemiology to determine the vulnerable stages in the life cycles of the pathogens that can be disrupted to achieve more effective disease control.

As befits a volume in the Advanced Series in Agricultural Sciences, this book was written with problems of practical agriculture in mind. One of the ways of controlling plant disease is by using resistant cultivars; and from the wide literature of genetics and biochemistry in plant pathology I have emphasized what seems to bear most closely on breeding for disease resistance. This has a double advantage, for it happens all to the good that this emphasis is also an emphasis on primary causes of disease, as distinct from subsequent processes of symptom expression and other secondary effects. The chapters are entirely modern in outlook. The great revolution in biology this century had its high moments in the elucidation of the DNA double helix in 1953 and the deciphering of the genetic code in 1961. This book, so far as I know, is the first in plant pathology to be conceived within the framework of this new biology. Half the book could not have been written 20 years ago, even if there had then been available all the literature that has since accumulated on the genetics and chemistry of plant disease. The new biology is the cement this book uses to bind the literature together. Another feature of this book is an emphasis on thermodynamics.

Using molecular methods for plant disease diagnosis provides diagnosticians with a number of advantages over more traditional methods. They can allow the identification of morphologically similar species, for example, or the detection of infection prior to symptom formation. Not only can molecular tools help by increasing the efficacy, accuracy and speed of diagnosis; their common technological basis provides further benefits, especially where resources are limited and traditional skills are hard to sustain. This book provides protocols for nucleic acid-based methods currently applied to plant pathogen detection and identification. It takes the practitioner through the full range of molecular diagnostic and detection methods and, as these generic techniques are appropriate for use on any target with minimal modification, also provides a useful resource for students of plant pathology and plant pathologists. Beginning with the background and future directions of the science, it then addresses DNA barcoding, microarrays, polymerase chain reactions (PCR), quality assurance and more, forming a complete reference on the subject.