Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Pear cultivars when grafted on Pyrus serotina or P. ussuriensis shows quick decline
Reason (R) : Mycoplasma damages the xylem tissue at graft union depriving the roots of food material
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

Phytoplasmas and mycoplasma-like organisms are strictly phloem-limited pathogens. Any statement claiming they damage the xylem is physiologically incorrect.

Answer 1

The Correct Option is C

To determine the correct answer, let's analyze the Assertion (A) and the Reason (R) provided:

1. Assertion (A): Pear cultivars when grafted on Pyrus serotina or P. ussuriensis show quick decline.
   • This statement is generally known to be true in horticulture. Pear cultivars can indeed show a quick decline when grafted onto these rootstocks due to incompatibility issues that are often unrelated to disease but more due to physiological and biochemical mismatches between the scion and the rootstock.
2. Reason (R): Mycoplasma damages the xylem tissue at graft union, depriving the roots of food material.
   • This reason suggests that Mycoplasma (a type of bacteria that lacks a cell wall) is responsible for the decline by damaging xylem tissue at the graft junction. While Mycoplasma can impact plant health, it mainly targets phloem tissue, causing systemic infections, and there is no concrete evidence that it specifically causes xylem damage at the graft union leading to quick decline in this context.

Based on the above analysis:

• The Assertion is correct as grafting pear cultivars onto Pyrus serotina or P. ussuriensis can cause quick decline.
• However, the Reason provided is not correct because while it addresses plant health issues, it inaccurately attributes graft union decline to Mycoplasma damaging xylem tissue.

Therefore, the correct answer is that (A) is correct but (R) is not correct.