Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R).
Assertion (A): The secondary spread of the pathogen propagules that are identical in virulence is mostly responsible for epidemics.
Reason (R): Secondary propagules are mostly asexually produced.
In light of the above statements, choose the correct answer from the options given below.
Assertion (A): The secondary spread of the pathogen propagules that are identical in virulence is mostly responsible for epidemics.
Reason (R): Secondary propagules are mostly asexually produced.
In light of the above statements, choose the correct answer from the options given below.
Show Hint
Because mitosis produces identical clones, a single virulent spore can quickly multiply into billions of identical, highly virulent spores that trigger an epidemic.
- Both (A) and (R) are true and (R) is the correct explanation of (A).
- Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
- (A) is true but (R) is false.
- (A) is false but (R) is true.
The Correct Option is A
Solution and Explanation
Plant disease epidemics, especially in polycyclic diseases (diseases with multiple infection cycles per season), develop rapidly through the generation and dispersal of secondary inocula.
The genetic uniformity of these secondary propagules plays a key role in their ability to quickly colonize susceptible crop hosts over vast geographical areas.
Step 2: Detailed Explanation:
The initiation of an epidemic begins with a primary infection, often established by sexually produced or overwintering structures.
Once established, the pathogen switches to rapid secondary reproduction.
The primary driving force behind the explosive growth of an epidemic is the massive release of secondary propagules (such as urediniospores in rusts or conidia in mildews).
Because all these secondary spores target the same host crop, they must share the identical virulence profile to successfully infect the plants, making Assertion (A) true.
Reason (R) states that these secondary propagules are mostly asexually produced.
Asexual reproduction involves mitotic cell divisions, which bypasses genetic recombination.
This ensures that the massive numbers of spores produced are genetically identical clones of the parent pathogen, preserving the exact virulence genes needed to overcome host resistance.
Therefore, because the secondary propagules are produced asexually (R), they are genetically identical in virulence, which allows them to rapidly spread and drive the epidemic (A).
Thus, both statements are true, and the Reason provides a clear biological explanation for the Assertion.
Step 3: Final Answer:
Both (A) and (R) are true and (R) is the correct explanation of (A).
Top ICAR AIEEA Plant Sciences Questions
- Both plant and animal cells contain some small organelles called 'peroxisomes', which are dedicated to the metabolism of substances such as
- Chemicals that store energy for the majority of work within cells are called
- The longest phase during the eukaryotic cell cycle is
- The formula: [Sum of (Observed-Expected)$^2$/Expected] is also known as
- Human beings have a large-sized 'proteome'. The principal and more significant reason for this is-
Top ICAR AIEEA Microbiology Questions
- Choose the correct order of the following microbes based on their requirement of host - from dead to living
(A). Saprotrophs
(B). Biotrophs
(C). Hemibiotrophs
(D). Nectrotrophs Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R).
• [Assertion (A):] Biotrophs can be easily cultured in artificial medium.
• [Reason (R):] Biotrophs lost their independent growth due to co-evolution with the host.
In light of the above statements, choose the most appropriate answer from the options given below:
Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R).
• [Assertion (A):] Phytoplasma do not have cell wall and motility.
• [Reason (R):] Phytoplasma colonize phloem.
In light of the above statements, choose the correct answer from the options given below.
Given below are two statements:
• [Statement (I):] Bacteria need pre-existing openings or wounds on plants to initiate infection.
• [Statement (II):] Bacteria do not produce specialized infective structures.
In light of the above statements, choose the most appropriate answer from the options given below.
Which of the following traits are observed in eukaryotes but not in prokaryotes?
• [(A).] 70S ribosomes
• [(B).] Nuclear division by Mitosis
• [(C).] Phagocytosis
• [(D).] Binary fission
• [(E).] Presence of Nucleolus
Choose the correct answer from the options given below:
Top ICAR AIEEA Questions
- Which of the following statements is false?
- Which of the following is an example of an inventory?
- According to Adam Smith, productivity gains could be brought about through .
- The supply curve for an artificially scarce good is .
- Which of the following would not be considered an opportunity cost of paid employment?