Fungicides and Metabolite Standards
Introduction of Fungicides
Plant disease is one of the natural disasters that seriously endanger agricultural production. Plant diseases can not only reduce crop yields, but also seriously threaten the quality and safety of agricultural products and their international trade to a certain extent. The history of chemical control of plant diseases has developed along with the occurrence of plant diseases. In the long-term struggle against natural disasters, a series of fungicides have been developed for the control of plant diseases.
Fungicides are a class of chemicals used to control plant diseases. Fungicides are chemical substances that have poisoning and inhibitory effects on plant pathogens or can change the pathogenic process of pathogens or improve plant disease resistance.
Infection cycle of fungal diseases of plants
The Mechanism of Fungicides
The mechanisms of fungicides include affecting cell structure and function, inhibiting respiration, interfering with the synthesis and function of metabolites, and inducing disease resistance in host plants.
1. Affect Cell Structure and Function
- Affect the formation of fungal cell walls
Fungicides can inhibit or kill fungi by inhibiting the synthesis of polysaccharides in the fungal cell wall or by combining with polysaccharides and glycoproteins to destroy the cell wall structure. Damage to chitin is the most severe disruption of cell wall function by fungicides. - Affect the biosynthesis of fungal cell membranes
The bacterial cell membrane is composed of many subunit structures containing fats, proteins, and sterols. Each subunit is linked by metal bridges and hydrophobic bonds. There are two situations in which fungicides damage the cell membrane and inhibit the function of the membrane, namely physical damage and chemical inhibition. Physical damage refers to the combination of the biocide with the metal bridges or hydrophobic bonds connecting the subunits on the membrane, resulting in the destruction of the membrane structure. Chemical inhibition refers to the inhibition of the activity of enzymes related to membrane performance and the biosynthesis of sterols and sterols in membrane lipids.
2. Inhibit Respiration
Bactericides mainly inhibit the biological oxidation (respiration) of the bacteria by inhibiting various enzymes or affecting electron transfer or oxidative phosphorylation, and destroying the energy metabolism of the bacteria to achieve the purpose of sterilization.
3. Interfere with the Synthesis and Function of Metabolites
By interfering with the synthesis of important life substances in the bacteria, the fungicides hinder the normal growth and development of the bacteria, reduce the pathogenic ability, and even die, mainly including the synthesis and function of nucleic acids, proteins, enzymes and mitosis.
4. Induce Disease Resistance in Host Plants
Such fungicides have no bactericidal or bacteriostatic effect on pathogenic bacteria, but can induce host plants to produce resistant anti-disease activators or produce active substances against pathogenic bacteria to exert bactericidal effect. The application of such fungicides can induce systemic resistance in host plants, that is, plants are activated by abiotic or biotic factors in the environment, resulting in the characteristics of resistance to subsequent pathogenic infection. Such fungicides do not directly act on pathogenic bacteria, and the risk of drug resistance development is greatly reduced.
Classification of Fungicides
1. Mode of Action
According to the mode of action of fungicides on the control object, they are usually divided into the following four categories:
- Protective Fungicides
Protective fungicides are in direct contact with pathogenic bacteria outside or on the body surface of plants, killing or inhibiting pathogenic bacteria so that they cannot enter plants, thereby protecting plants from the harm of pathogenic bacteria. This type of fungicide does not enter the body of the plant, but only deposits on the surface of the plant for protection. Protective fungicides mainly include inorganic sulfur fungicides, copper preparations, organic sulfur fungicides, substituted benzene fungicides, antibiotic fungicides, etc. - Systemic Fungicides
Systemic fungicides are applied to a certain part of the plant and can be absorbed by the plant and transported to other parts of the plant to take effect. Plant diseases can be controlled by means of chemical protection and chemical treatment. Systemic fungicides mainly include organophosphorus fungicides, benzimidazole fungicides, imidazole fungicides, triazole fungicides, benzamide fungicides, etc. - Eradicating Fungicides
Eradicating fungicides can directly kill pathogenic bacteria near the entry point to terminate the parasitic relationship between pathogenic bacteria and host plants. - Plant-induced Disease Resistance Activators
Plant-induced disease-resistance activators refer to a class of fungicides that can enable plant systems to acquire disease resistance and improve plant resistance to pathogen invasion after application.
2. Chemical Structure
According to chemical structure, fungicides can be divided into inorganic fungicides and organic fungicides. Organic fungicides include Amide fungicides, phenylamide fungicides, imidazole fungicides, triazole fungicides, pyrimidine fungicides, methoxyacrylate fungicides, pyridine fungicides, pyrrole fungicides, etc.
- Inorganic Fungicides
Inorganic fungicides are a class of fungicides widely used in chemical control of plant diseases. Inorganic fungicides mainly include three categories: copper preparations (such as Bordeaux mixture, cupro ammonia mixture, copper sulfate), sulfur preparations (such as lime sulfur mixture, sulfur), and mercury preparations (such as mercuric chloride).
- Amide Fungicides and Metabolite Standards
- Phenylamide Fungicides and Metabolite Standards
- Imidazole Fungicides and Metabolite Standards
- Triazole Fungicides and Metabolite Standards
- Pyrimidine Fungicides and Metabolite Standards
- Strobilurin Fungicides and Metabolite Standards
- Pyridine Fungicides and Metabolite Standards
- Pyrrole Fungicides and Metabolite Standards
- Other Fungicides and Metabolite Standards
