Plant Pathology Short question 2

 Q. 1. What is non-parasitic plant disease?

Ans. When the disease is caused by non-parasitic causal agent it is called non-parasitic plant disease.

Q. 2. What is an alternate host?

Ans. When a pathogen needs two hosts to complete its life cycle then one host is designated as the principal host and the other as alternate host.

Q. 3. What is pathogenesis?

Ans. The chain of metabolical event which brings about the disease is pathogenesis.It involves the action of the pathogen, susceptibility of the plant and impact of the environment.

Q. 4. Name one toxin produced by a plant pathogen.

Ans. Wild fire toxin produced by Pseudomonas tabaci.

Q. 5. What is disease triangle?

Ans.In order for disease to occur, three factors must be present. Because of this,disease is often pictured as a triangle having three equal sides. Each side of the disease triangle is necessary in order for disease to occur. The three factors are host, causal agent and environment.

Q. 6. What is a disease cycle?

Ans. In every infectious disease a series of more or less distinct events occur in succession and leads to the development and perpetuation of the disease and the pathogen. This chain of events are called disease cycle.

Q. 7. Define host defense mechanism. 

Ans. The mechanism by which the plants protect themselves from the unfavourable environment or from a pathogen is called defense system or defense mechanism.

Q. 8. What is structural defense mechanism?

Ans. To protect the host from the pathogen or environment occurs some structural modifications.These structural modifications act as first line barrier of the plant for pathogen or environmental hazards.

Q. 9.What is PR protein?

Ans. PR protein are pathogen-related protein. They are generally a group of plant protein that are toxic to invading fungal pathogen or other pathogen.

There are many PR proteins - PR1, PR2 etc.

10. What is hypersensitivity?

The term denotes increased sensitivity as in the rapid death of a host cell in the immediate vicinity at the site of infection.

Q. 11. What is VAM?

Ans. VAM is Vasicular Arbuscular Mycorrhizae. This type of fungi are endomycorrhizal which invade deeply into the root. It has been observed that VAM are abundantly present in herbaceous plant growing in cultivated soil and grasslands.

12.What is Bordeaux mixture?

Bordeaux mixture is a chemical which is used for control of disease. 4:4:50,5:5:50 ratio of copper sulphate, quicklime and water mixture forms Bordeaux solution.

Q. 13. Define suppressive soil.

Ans. Several soil-born pathogens (Phytopthora sp) can infect a host much rapidly through live in a particular soil but when they are transferred to other soil the potentiality of those pathogens to form a disease become less. Then the later soil is called supressive for those particular pathogens. It is due to that the soil destructs the inoculum by resident antagonists.

Q. 14. What are biotrophs?

Ans. Parasitic organisms which are deriving their nutrients from living host cell.

Q. 15. What are necrotrophs?

Ans. The organisms which derive their nutrients from cells they have already killed. Most biotrophs cause minimal damage to the host tissue.

Q. 16.What is symbiosis?

Ans. In some cases two living organisms may live non-pathogenically in association with one another. In such cases both organisms are mutually benefited through their life processes. The phenomenon is known as symbiosis.

Q. 17. What do you mean by endemic disease?

Ans. A disease which constantly occurs from year to year in moderate to severe form in a particular area is an endemic disease.