Sustainable Approaches to Controlling Plant Pathogenic Bacteria

V. Rajesh Kannan, Kubilay Kurtulus Bastas

• Publisher: CRC Press
• Year: 2015
• ISBN:
  9781498782494
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Botany
• Index: Biological Sciences

Plant diseases and changes in existing pathogens remain a constant threat to our forests, food, and fiber crops as well as landscape plants. However, many economically important pathosystems are largely unexplored and biologically relevant life stages of familiar systems remain poorly understood. In a multifaceted approach to plant pathogenic behav

Chapter 1

Plant Pathogenic Bacteria

An Overview

Velu Rajesh Kannan, Kubilay Kurtulus Bastas, and Robert Antony

Abstract Phytopathology is an interdisciplinary biological science that comprises botany, microbiology, crop science, soil science, ecology, genetics, biochemistry, molecular biology, and physiology. In general, plant diseases are caused by living organisms (called pathogens) and by nonliving agents. Plant diseases and changes in existing pathogens remain a constant threat to our forests, food and fiber crops, and landscape plants. However, many economically important pathosystems are largely unexplored and biologically relevant life stages of even familiar systems remain poorly understood. Development of new and innovative ways to control plant diseases is a constant challenge for plant pathologists. The modern mindset in this context favors a broad perspective that considers multifaceted approaches to plant pathogenic bacterial control. This chapter, which discusses impact of plant pathogenic bacterial pathogenesis on scientific and economic levels, introduces the various mechanisms, measuring tools, and controlling strategies that will be elaborated in the following chapters.

Keywords: plant pathogen, phytopathology, plant bacterial disease, pathosystem, disease-controlling strategy

1.1 Introduction

The immense diversity of plant pathogens, which include viruses, bacteria, fungi, nematodes, and insects, approximates 7100 species. Among these, roughly 150 are bacterial species that cause diseases to plants. The major ways that bacterial pathogens cause plant diseases are by obtaining nutrients one or more host plants for their own growth; using specific mechanisms to secrete proteins and other molecules to locations on, in, and near their hosts; and by exploiting these proteins and other molecules modulate or avoid plant defense circuitry to enable parasitic colonization (Chisholm et al., 2006; Davis et al., 2008). Bacterial plant diseases are most frequent and severe in tropical and subtropical places, where warm and humid conditions are ideal for bacterial growth. Indeed, consistent annual crop losses are recorded in all countries.

The problem of plant diseases, particularly in developing countries, is aggravated by the paucity of resources devoted to pathological studies. This gap in the literature may be the result of an inability to quantify plant diseases, followed closely by an inability to relate information about plant diseases to the failure of crops to reach manageable yields. In general, plant pathogenic bacterial species belonging to Xanthomonadaceae, Pseudomonadaceae, and Enterobacteriaceae families target all types of plants that can supply them with appropriate food and shelter. The most devastating plant pathogens belong to genera such as Erwinia, Pectobacterium, Pantoea, Agrobacterium, Pseudomonas, Ralstonia, Burkholderia, Acidovorax, Xanthomonas, Clavibacter, Streptomyces, Xylella, Spiroplasma, and Phytoplasma.

1.2 Pathogenesis of Plant Pathogenic Bacteria

Plant bacterial diseases are generally characterized by plant morphological symptoms such as leaf and fruit spots, cankers, blights, vascular wilts, rots, and tumors. Phytopathogenic bacteria provoke diseases in plants by penetrating into host tissues (Buonaurio, 2008). Microbial pathogenicity has often been defined as the biochemical mechanisms whereby pathogenic microorganisms cause disease in a host organism (Fuchs, 1998). Microbial virulence is defined as the degree or measure of pathogenicity shown by one or more plants. Pathogenicity and/or virulence of Gram-negative plant pathogenic bacteria are strictly dependent on the presence of secretion apparatuses in host cells, through which they secrete proteins or nucleoproteins involved in their virulence within the apoplast or inject these substances into host cells (Buonaurio, 2008).

Bacterial pathogens contain several classes of genes, called virulence genes, that are essential for causing disease or for increasing virulence in one or more hosts. Pathogenicity factors that are encoded by pathogenicity genes (pat) and disease-specific genes (dsp) are crucially involved in the establishment of diseases. Some of these genes are essential for the recognition of a host by a pathogen, attachment of a pathogen to a plant’s surface, formation of infection structures on or within the host, penetration of the host, and colonization of host tissue. The pathogenicity genes that are involved in the synthesis and modification of the lipopolysaccharide cell wall of Gram-negative bacteria may help condition the host range of a bacterium.

Plant pathogenic bacterial virulence factors are associated with the bacterial surface or secreted into the surrounding environment. Proteins secreted by bacteria are transported via molecular systems out of bacterial cells; unrelated virulence factors often share the same secretion mechanism (Fuchs, 1998). Bacterial pathogenicity depends upon bacterial secretion systems (types i–iv), quorum sensing (QS), plant cell-wall-degrading enzymes, toxins, hormones, polysaccharides, proteinases, siderophores, and melanin. All of these systems and substances, which are essential for pathogenic infection and virulence, are produced by pathogens during bacterial pathogen–plant interactions (Agrios, 2005). They are all regulated by proteins through signal transduction systems.

A case study of the infection process of Rhizobium radiobacter (Agrobacterium tumefaciens), the causal agent of crown gall in many fruit and forest trees, vegetables, and herbaceous dicotyledonous plants from 90 f...

Table of contents

• Foreword
• Preface
• Editors
• Contributors
• Chapter 1 - Plant Pathogenic Bacteria: An Overview
• Chapter 2 - Pathogenesis of Plant Pathogenic Bacteria
• Chapter 3 - Epidemiology and Forecasting Systems of Plant Pathogenic Bacteria
• Chapter 4 - Controlling Strategies (Diagnosis/Quarantine/Eradication) of Plant Pathogenic Bacteria
• Chapter 5 - Agro-Traditional Practices of Plant Pathogens Control
• Chapter 6 - Antimicrobial Polypeptides in the Control of Plant Pathogenic Bacteria
• Chapter 7 - Nutrient Supplements for Plant Pathogenic Bacteria: Their Role in Microbial Growth and Pathogenicity
• Chapter 8 - Biocontrol Mechanisms of Siderophores against Bacterial Plant Pathogens
• Chapter 9 - Plant Metabolic Substances and Plant Pathogenic Bacterial Control
• Chapter 10 - Host Resistance: SAR and ISR to Plant Pathogenic Bacteria
• Chapter 11 - Quorum Sensing in Plant Pathogenic and Plant-Associated Bacteria
• Chapter 12 - Cyanobacteria and Algae: Potential Sources of Biological Control Agents Used against Phytopathogenic Bacteria
• Chapter 13 - Arbuscular Mycorrhizal Fungi-Mediated Control of Phytopathogenic Bacteria
• Chapter 14 - Plant Growth-Promoting Rhizobacteria as a Tool to Combat Plant Pathogenic Bacteria
• Chapter 15 - Bacteriophages: Emerging Biocontrol Agents for Plant Pathogenic Bacteria
• Chapter 16 - Role of Defense Enzymes in the Control of Plant Pathogenic Bacteria
• Chapter 17 - Plant Pathogenic Bacteria Control through Seed Application
• Chapter 18 - Plant Pathogenic Bacteria Control through Foliar Application
• Chapter 19 - Modern Trends of Plant Pathogenic Bacteria Control
• Chapter 20 - Scientific and Economic Impact of Plant Pathogenic Bacteria