Molecular Biology of the Biological Control of Pests and Diseases of Plants

Muthukumaran Gunasekaran, Darrell Jack Weber

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000721911
• Edition: 1
• Topic: Biowissenschaften
• Subtopic: Botanik

While many books are available on biological control, this is the only book to detail the application of molecular biology to control of pests and diseases. Each chapter deals with a different pathogen and the application of new molecular biological techniques to the biocontrol of the pathogen.
This new reference presents the most comprehensive list of organisms available. Internationally respected experts discuss viruses, bacteria, fungi, nematodes, protozoa, weeds, and insects. Types of control methods are described, and techniques commonly used in molecular biology to identify the etiological agents, diagnose diseases, and develop control methods are reviewed.

1

Approaches to the Control of Pests and Diseases of Plants

Darrell Jack Weber and Muthukumaran Gunasekaran

TABLE OF CONTENTS

I. Impact of Diseases and Pests

II. Host and Parasite Relationships

III. Host Resistance

IV. Approach to Control of Plant Diseases and Pests

A. Physical Control N4ethods

B. Chemical Control Methods

C. Biological Control

V. Molecular Biology Approach: Historical Development

A. The PCR Technique

B. The RFLP Technique

C. The RAPD Technique

D. Transformation Techniques

VI. Changing the Resistance of the Host With Techniques Used in Molecular Biology

A. Transferring Resistant Pathogen Genes into Host Plants

B. Insertion of Resistant Genes from Another Type of Plant Species

C. The Mechanism of Gene Transfer Resistance

VII. Changing the Parasite With Techniques Used in Molecular Biology

VIII. Modifying the Factors That Involve the Virulence of the Pathogen

A. Virus Synthesis Blockage

B. Blockage of Virus Movement from Cell to Cell

IX. Summary

References

I. Impact of Diseases and Pests

Food surpluses and food shortages occur at the same time in the world today. However, food shortages are a more serious matter. Several famine relief efforts have been undertaken to help in the impoverished areas, particularly in Africa. It is estimated that 800 million people are undernourished, and as many as 2 billion may be suffering from hunger or malnutrition. With the world population near 6 billion and still growing, the question of food production becomes an important concern. Directly related to food production are losses caused by pests and diseases. It is estimated that for the entire world, the percent of crop loss due to diseases, insects, and weeds is about 34%.¹ The estimated percent loss caused by each individual group is 11.9% by diseases, 12.3% by insects, and 9.8% by weeds.² An additional 15% food loss could be added due to postharvest pests and diseases.¹ This suggests that the total impact of pests and diseases results in the loss of almost half of the food produced in the world. Effective control of pests and diseases would result in a tremendous increase in food. The amount of loss is less in the developed nations as compared to the developing nations. Ironically, developing nations have a much greater number of their population (57%) engaged in agriculture, but their losses are still higher. Much of the success in controlling pests and diseases in developing nations has been due to the application of large quantities of chemical pesticides. Many of the pesticides are no longer effective due to the development of resistance to the chemical by the pest. In other cases the pesticide has been barred from use because it did not pass reregistration. There is increased concern about using pesticides in the environment because of potential contamination of ground water and foodstuffs.³ For developing nations, pesticides are a major expense in crop production. On the other hand, pesticides are the most effective means of controlling pests and diseases.

Alternate nonpesticide methods of controlling pests and diseases would be very desirable. Biological control, the suppression or destruction of pests and diseases with living organisms, has the appeal of a reliable and safe alternative to high pesticide use. Biological control is not a new concept. It has been around a long time. There is a record of the ancient Chinese using the ant, Oecophylla smaragdina, to control caterpillars and beetles on citrus trees in 324 B.C. In 1752, Linnaeus suggested that insects could be used to control other insects.⁴ In 1884, Krassilstschick⁵ grew the fungus Metarrhizium and used the spores to control the sugar beet curculio larvae (Cleonus punctiventris).⁴ The first great success in classical biological control of insects occurred in 1889 in the control of cottony cushion scale in California by using the parasitic fly, Crytochetum iceryae.⁴

Biological control of weeds started in 1863 with the use of the cochineal insect, Dactylopius ceylonicus, to control prickly pear cactus in India. The control of Klamath weed in California in 1946 by the introduction of Chrysolina quadrigemina (Suffrian) was a successful application of biological control. It is estimated that the abundance of Klamath weed was reduced by 99%.⁶

The strategy for obtaining biological control of pests normally involves three approaches using natural enemies: (1) Importation of exotic species and their establishment in a new habitat; (2) augmentation of established species through direct manipulation of their populations by mass production and periodic colonizations; (3) the conservation of natural enemies by manipulations of the environment.⁴

Biological control of plant disease involves the use of antagonistic microorganisms that interact with the parasite to reduce its effectiveness. In the widest sense, biological control of plant diseases can include crop rotation, direct addition of microbes antagonistic to pathogens, use of chemicals to change the microflora, and plant breeding to develop resistant plants.⁷ A range of success in biological control of plant diseases has been obtained. Perhaps most effective has been the breeding of resistance plants.

II. Host and Parasite Relationships

A parasite can be defined as an organism that lives on or in some other organism and obtains its food from the host organism. The interaction between the host and the pathogen is not a passive process but rather an active interaction. The weapons of the pathogens include the ability to physically penetrate the host cell, the secretion of degraded enzymes, production of microbial toxins that weaken or damage the host, synthesis of polysaccharides that can plug the water flow in the xylem of the host, and production of auxins that stimulate the host to respond to the pathogen.⁸

On the other hand, plant hosts protect themselves against pathogen attack by: having preexisting physical structures that prevent the entry of the pathogen, forming protective cork layers when infected, forming abscission layers around the infection area to isolate the pathogen, producing tyloses and gums that localize and restrict the movement of the pathogen, synthesizing of phytoalexins that are inhibitory to pathogens, producing phenols which are normally toxic to the pathogen, detoxifying fungal toxins by enzymatic action, and sacrificing some of their own cells which also kill the pathogen through the hypersensitive reaction.⁸

The interaction between the host and the pathogen is a dynamic process. In biological control, another organism which is antagonistic to the pathogen and favorable to the host is involved in the host-parasite interaction.

Insects can directly penetrate the host or consume part of the host. In some cases, the insect injects chemicals similar to plant hormones into the host which stimulate the host plant to produce galls and witches brooms.

While insects are very mobile, they often induce reactions similar to those of pathogens in the host. Host plants produce phytoalexins, phenolic complexes, and chemicals that are anti-feedants for insects.

III. Host Resistance

Over the centuries, plants have evolved resistance to many pathogens and pests. When new pathogens and pests are introduced or strains of existing pathogen and pests develop, if no natural resistance is present then major losses will occur in the crops. Plant breeding is a means of adding resistance to the crop plant in response to the presence of serious pathogens and pests.

Plant breeding for resistance in the host has many advantages. The resistant plant can be grown by culture methods similar to those already in practice. There is no need to apply pesticides to the environment. Because no pesticides are used, it is often less expensive to grow the crop.

Among the disadvantages of breeding for resistance is that it takes a number of years to develop the resistant variety. There must be a genetic resistant characteristic to the pathogen of concern in a plant that can be bred with the crop to develop a resistant variety. In many cases, it is not possible to find such resistance in another plant that can be cross-bred. In other cases, the genetic cross can be made but the hybrid is not fertile and the breeding program cannot continue. It requires many backcrosses to maintain the desirable agronomic characteristics in the plant while the resistant characteristics are being incorporated into the genetic system of the host plant.

Once a resistant variety has been developed, the parasite will often evolve and develop a strain that can break the resistance of the host. In many cases, this breakdown in resistance occ...

Table of contents

• Cover
• Half Title
• Copyright Page
• Table of Contents
• Preface
• The Editors
• Contributor
• Chapter 1 Approaches to the Control of Pests and Diseases of Plants
• Chapter 2 Molecular Approaches to Biological Control of Virus Diseases of Plants
• Chapter 3 Molecular Biology of the Biological Control of Plant Bacterial Diseases
• Chapter 4 Molecular Biology of Fungal Diseases
• Chapter 5 The Role of Molecular Biology in Developing Biological Controls for Plant Parasitic Nematodes
• Chapter 6 Genetically Enhanced Baculovirus Insecticides
• Chapter 7 Molecular Biology of Bacteria for the Biological Control of Insects
• Chapter 8 Molecular Biology of Fungi for the Control of Insects
• Chapter 9 Molecular Biology of Protozoa for Biological Control of Harmful Insects
• Chapter 10 Molecular Biology of Bacteria and Fungi for Biological Control of Weeds
• Chapter 11 Integrated Pest Management Strategies
• Chapter 12 Future Considerations
• Index