Plant Disease Management

Principles and Practices

Hriday Chaube

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9781351092623
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Biology
• Index: Biological Sciences

This book attempts to provide to provide concise, critical, synthetic and up-to-date coverage of different aspects of plant disease management. The first eleven chapters are devoted to principles and related aspects and the remining seven to management practices based on them. The book attempts to capture some of the images of such rapidly expanding fields as host-parasite recognition and biotechnology even at the risk of making the subject a bit conceptual. This book is intended to serve as a text for advanced undergraduate and graduate students of plant pathology and related disciplines and as a reference source for teachers, researchers, students, and technologists.

Chapter 1
The Plant Pathogens

I. Introduction

Organisms suffer from disease or disorders due to some abnormality in the functioning of their system. These abnormalities may be due to factors which have no biological activity of their own (abiotic factors) or those entities which show some biological activity (mesobiotic agents) and those that are established cellular organisms. A pathogen can be broadly defined as any agent or factor that induces pathos or disease in an organism, but the term is generally used to denote biotic and mesobiotic causes.

Which factor, entity or agent should be called abiotic and which one biotic or living? By institution and experience we have known that a thing that does not grow, reproduce, move, or show response to external stimuli is nonliving and those things that show these properties are living. However, when viruses appear in the picture, the whole concept of living vs. nonliving becomes somewhat confused.

II. Cellular Organisms and Viruses

Although viruses are acellular, they always have one type of nucleic acid and in those that have RNA, the latter performs the same functions as the DNA in cellular organisms. Consequently, there is reproduction of different type, regulation of the activities whatever they may be, and existence of the phenomena of variability. They do have proteins but only of structural type. They synthesize the enzyme for replication with the help of host ribosomes; some have the replicative enzyme in the capsid, and some use the host enzymes. One major nonliving character of viruses is the ability of the nucleic acid to retain activity even after chemical purification and crystallization. These entities are, therefore, considered not true organisms but at the threshold of life. The basic differences between viruses and cellular organisms are summarized in the Table 1.

III. Division of Organisms

When the living organisms were divided into plant and animal kingdoms, fungi were included among the plants. The complex and heterogenous behavior of many lower organisms created limitations in this system. To solve this problem, E. Haeckel, a German biologist proposed a third kingdom Protista (Protisto = very first) about a century ago (1866) to include organisms which lacked tissues. Protists themselves were later divided into lower and higher protista. The lower protista which included bacteria and blue green algae, was named the fourth kingdom, Monera. Thus, the living world came to have four kingdoms, i.e., Plantae, Animalia, Protista, and Monera (synonym = Mychota).^1,2 Whittaker³ proposed a five-kingdom system and placed fungi in a separate kingdom, coordinate with higher plants and animals. The two primitive kingdoms are the Monera (prokaryotic-organisms bacteria and blue-green algae) and Protista (unicellular-eukaryotic organisms).

The development of electron microscope and associated preparative techniques for biological materials made it possible to study the ultra-structures in the cell such as intranuclear-intranucleolar structures, cell organelles other than nuclei, membrane of the cell and intracellular organelles, etc. These observations led to the recognition of two kinds of cells in the living systems. In the more complex eukaryotic cell, which is the unit of structure in plants, metazoan animals, protozoa, fungi, and most algae, the nucleus is bound by a nuclear membrane and divides by mitosis.

TABLE 1
Differences Between Viruses and Cellular Organisms

Trait	Viruses	Organisms
Basic unit of structure and function	Nucleocapsid consisting or nucleic acid core and protein coat of shell	Cell
Nucleic acid components	Either RNA or DNA	Both RNA and DNA
Enzyme content	One or a few enzymes	Many enzymes
Reproductive process	Nucleic acid core separates from capsid, replicates forming own replica and proteins separately which assemble to form a new capsid; nucleo-capsides never yield progeny capsids directly	Progenitor cells yield cells directly by different processes of reproduction; parents retain identity; cellular identity never lost
Dependence on another organism	Always obligately dependent on a commandeered cellular organism	Usually independent, microbes sometimes facultatively dependent, rarely obligately dependent
Location in other organism	Always within the cell; intracellular, intramembranous, etc.	Only parasitic forms have different types of inter-and intracellular relationship

The less complex prokaryotic cells are the unit of structure in two microbial groups, the bacteria including mycoplasmas and rickettsiae, and the blue-green algae or blue-green bacteria. The prokaryotic nucleus (nucleoid) is not membrane bound and its division is nonmitotic. This unambiguous bipartite division of organisms, exclusively based on cellular properties still retains algae, fungi, and protozoa in the protists as eukaryotes distinct from plants and animals on the basis of little or no differentiation of cells and tissues as given below.

The primary sub-division of cellular organisms

Eukaryotes	1. Multicellular, extensive differentiation of cells and tissues	A. Plants
		a. seed plants
		b. ferns
		c. mosses
		d. liverworts
		B. Animals
		a. invertebrates
		b. vertebrates
	2. Unicellular, coenocytic ...

Table of contents

• Cover
• Title
• Copyright
• PREFACE
• THE AUTHORS
• Dedication
• ACKNOWLEDGMENT
• Contents
• Chapter 1 The Plant Pathogens
• Chapter 2 Plant Diseases
• Chapter 3 Disease Development
• Chapter 4 Host-Parasite Interaction
• Chapter 5 Principles and Practices of Plant Disease Management
• Chapter 6 Diagnosis of Plant Diseases
• Chapter 7 Survival of Plant Pathogens
• Chapter 8 Dissemination of Plant Pathogens
• Chapter 9 Pathometry-Assessment of Disease Incidence and Loss
• Chapter 10 Epidemiology of Plant Diseases
• Chapter 11 Plant Disease Forecasting
• Chapter 12 Regulatory Methods
• Chapter 13 Physical Methods
• Chapter 14 Biological Control
• Chapter 15 Cultural Practices
• Chapter 16 Host Resistance and Immunization
• Chapter 17 Chemical Control
• Chapter 18 Integrated Pest (Disease) Management (IPM)
• INDEX