56. The following are statements above molecular markers in the context of plant breeding
A. Molecular markers can be used for elimination of undesirable traits
B. Molecular markers cannot be used for elimination of genetic contribution of each individual parent in a segregating population
C. Molecular markers are used for mapping of QTLs, which is also possible by conventional techniques.
D. Molecular markers can be used for selection of individuals from a population that are homozygous for the recurrent parent genotype at loci flanking the target locus.
Which of the above statements are TRUE?
(1) A and B      (2) A and C
(3) A and D      (4) B and C

Correct option: A and D

Statement A

A. Molecular markers can be used for elimination of undesirable traits

• Molecular markers allow indirect selection against alleles linked to undesirable traits by identifying and discarding genotypes carrying those marker alleles, especially at seedling or early stages.

• In marker-assisted selection (MAS) and marker-assisted backcrossing (MABC), breeders routinely use markers to remove genotypes with unwanted donor segments (linkage drag), effectively “eliminating” undesirable traits from the breeding population.

✅ Therefore, Statement A is TRUE.

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Statement D

D. Molecular markers can be used for selection of individuals from a population that are homozygous for the recurrent parent genotype at loci flanking the target locus.

• In marker-assisted backcross breeding, “background selection” uses markers across the genome to recover the recurrent parent genome as quickly as possible, including at loci flanking the target gene.

• Individuals homozygous for the recurrent parent alleles at flanking markers are selected to minimize linkage drag and to ensure that only the desired introgressed segment around the target locus is retained.

✅ Therefore, Statement D is TRUE.

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Incorrect options: B and C

Statement B

B. Molecular markers cannot be used for elimination of genetic contribution of each individual parent in a segregating population

• In segregating populations (e.g., F2, backcross, RILs), molecular markers are precisely used to estimate and track the contribution of each parent’s genome, locus by locus.

• Through marker data, breeders can select individuals with reduced donor genome and increased recurrent parent genome, i.e., they actively reduce (“eliminate”) the unwanted parental contribution in specific regions.

❌ Statement B is FALSE because molecular markers are exactly used to monitor and reduce genetic contribution from a given parent.

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Statement C

C. Molecular markers are used for mapping of QTLs, which is also possible by conventional techniques.

• QTL mapping fundamentally relies on DNA markers to detect associations between marker genotypes and quantitative trait variation; without molecular markers, standard QTL mapping as used in modern breeding is not possible.

• Conventional phenotypic selection can handle quantitative traits but does not “map” QTL as genomic regions in the strict sense; true QTL mapping is a marker-based statistical procedure.

❌ Statement C is considered FALSE in this MCQ context, because QTL mapping is a molecular-marker-based approach and cannot be done in the same way by purely conventional, non-marker techniques.

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MCQ result

• True: A, D

• False: B, C

So the correct option is (3) A and D.

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Introduction

Molecular markers in plant breeding have transformed selection strategies by allowing breeders to track genomic segments linked to desirable and undesirable traits with high precision, especially in backcross and segregating populations. This solved MCQ on molecular markers in plant breeding clarifies how markers are used to eliminate undesirable traits, dissect quantitative trait loci (QTL), and select individuals homozygous for the recurrent parent genome around target loci.

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Explanation of each statement

Statement A: Elimination of undesirable traits

• In marker-assisted selection, DNA markers closely linked to undesirable alleles allow discarding seedlings carrying those markers long before full phenotyping, thus eliminating undesirable genotypes early.

• This reduces population size, saves cost and time, and accelerates fixation of favorable alleles, so A is true within the context of MAS.

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Statement B: Genetic contribution of each parent

• Using polymorphic markers between parents, breeders can estimate genomic contribution from each parent in progeny and select individuals with minimized donor genome (except the target region).

• Therefore, it is incorrect to say markers “cannot be used” for elimination of parental contribution; they are actively used for that purpose in background selection and recovery of the recurrent parent genome, so B is false.

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Statement C: QTL mapping and conventional methods

• QTL mapping, as defined in quantitative genetics, uses marker–trait associations in structured populations to locate genomic regions affecting quantitative traits; this process depends on molecular markers.

• While conventional breeding can improve quantitative traits via phenotypic selection, it does not “map” QTL as chromosomal regions without markers, so the assertion that QTL mapping is “also possible” by conventional techniques is misleading here, making C false.

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Statement D: Selection for recurrent parent genotype at flanking loci

• In marker-assisted backcrossing, background selection uses flanking markers around the target gene to choose plants that are homozygous for recurrent parent alleles at these loci, thereby reducing linkage drag.

• This approach ensures that only a minimal donor segment around the target locus is retained while the rest of the genome closely resembles the recurrent parent, so D is true.

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Summary table for quick revision

Thus, the correct option for this MCQ is (3) A and D.