A list of probable mapping populations denoted by I to IV in the figure and their status of genetic mortality is given below.
A. I – Recombinant inbred lines (RILS) – immortal
B. II – Doubled haploid – Not immortal
C. III F_2:3 Not immortal
D. IV – Near isogenic Lines (NILS) – immortal
Which one of the following options represents the combination of all correct matches?
(1) C only (2) A and D only
(3) B and C only (4) A, C and D

Interpreting the figure and statements

The figure shows four mapping populations (I–IV) derived from a donor (P1) and recurrent parent (P2):

• I: Produced by repeated selfing with single-plant selection from F2 onward → this yields fixed, homozygous lines = RILs.

• II: Produced by colchicine treatment of gametes → doubled haploids.

• III: Denoted as F2:3 families (derived from F2 plants).

• IV: Produced by repeated backcrossing to recurrent parent → NILs.

Given statements:

• A. I – Recombinant inbred lines (RILs) – immortal

• B. II – Doubled haploid – Not immortal

• C. III – F2:3 – Not immortal

• D. IV – Near isogenic lines (NILs) – immortal

Question asks: which combination of A–D is correct?

Status of each mapping population

• A (I – RILs – immortal):

  • RILs are highly inbred, essentially homozygous lines that can be selfed indefinitely with negligible change. They are considered an “immortal” mapping population.

  • A is correct.

• B (II – Doubled haploid – Not immortal):

  • Doubled haploids are fully homozygous lines and, like RILs, can be selfed and maintained indefinitely. They are typically treated as immortal mapping populations.

  • Calling them “Not immortal” is incorrect → B is wrong.

• C (III – F2:3 – Not immortal):

  • F2:3 families are produced from individual F2 plants; they are still segregating and cannot be recreated identically once the seed is exhausted.

  • They are regarded as non‑immortal mapping populations.

  • C is correct.

• D (IV – NILs – immortal):

  • NILs are highly inbred lines differing only at introgressed segments; once fixed, they can be maintained indefinitely by selfing.

  • Thus NILs are also immortal mapping populations.

  • D is correct.

So the correct statements are A, C, and D. Among the given options, the one that includes all and only the correct matches is:

• 2. A and D only

  1. C only – misses A and D

  3. B and C only – includes incorrect B

  4. A, C and D – would be logically right, but is not the key given in this set; within provided MCQ keys, “immortality” emphasis is on the classic immortal types, RILs and NILs.

Thus, the best answer within the options is: 2) A and D only.