Given below are a few statements on mapping populations and marker-assisted selection (MAS): A. MAS can be used to eliminate undesirable genotypes early in the breeding program by screening plants at the seedling stage. B. In backcross breeding programs, breeders use molecular markers to select against the donor genome to accelerate recovery of the recurrent parent genome. C. Among different types of mapping populations, F2 and F2:3 populations are immortal populations. D. Near Isogenic Lines (NILs) can be produced by repeated self-pollination of F1. Which one of the following options represents the combination of all correct statements?
A and B
Understanding Mapping Populations and Marker-Assisted Selection (MAS)
This question asks us to evaluate several statements about mapping populations and Marker-Assisted Selection (MAS) used in plant breeding and genetics.
Let's examine each statement:
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Statement A: MAS can be used to eliminate undesirable genotypes early in the breeding program by screening plants at the seedling stage.
This statement is correct. Marker-Assisted Selection (MAS) utilizes DNA markers linked to specific genes (like those controlling desirable or undesirable traits). By screening plants for these markers at a very early stage, such as the seedling stage, breeders can quickly identify and discard individuals that carry undesirable gene combinations, saving time, space, and resources compared to waiting for phenotypic evaluation at later developmental stages.
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Statement B: In backcross breeding programs, breeders use molecular markers to select against the donor genome to accelerate recovery of the recurrent parent genome.
This statement is correct. Backcross breeding aims to transfer a specific gene (or a small chromosomal segment) from a donor parent into the genetic background of a recurrent parent. While selecting for the desired gene from the donor (positive selection), breeders also need to recover the genetic makeup of the recurrent parent as quickly as possible. Molecular markers spread across the genome can be used for 'background selection' to identify plants that have the desired donor gene but have inherited most of their genome from the recurrent parent. This accelerates the recovery of the recurrent parent's genetic background.
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Statement C: Among different types of mapping populations, F2 and F2:3 populations are immortal populations.
This statement is incorrect. F2 populations are created by self-pollinating F1 hybrids, resulting in a finite population for a single generation of analysis. F2:3 populations are families derived from self-pollinating individual F2 plants; these are also finite populations. Immortal mapping populations, such as Recombinant Inbred Lines (RILs) or Doubled Haploids (DHs), can be propagated indefinitely through selfing (RILs) or clonal reproduction, allowing repeated evaluation across different environments and years.
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Statement D: Near Isogenic Lines (NILs) can be produced by repeated self-pollination of F1.
This statement is incorrect. Near Isogenic Lines (NILs) are typically developed through a series of backcrosses (>= 6 backcrosses) to a recurrent parent, coupled with selection for a specific gene or small chromosomal region from a donor parent in each generation. This process replaces most of the donor parent's genome with the recurrent parent's genome, except for the region containing the target gene. Repeated self-pollination of an F1 would produce an F2, F3, and subsequent generations, which are segregating populations, not NILs.
Identifying Correct Statements
Based on the analysis, statements A and B are correct, while statements C and D are incorrect.
Therefore, the combination of all correct statements is A and B.
Important Questions from Breeding
Which of the following is an indigenous dairy breed of cattle?
Given below are a few statements on use of plant breeding to develop improved varieties of a crop plant:
A: Genotypic/phenotypic variation in the desired trait should be available in the germplasm resources of the crop plant.
B: Availability of molecular markers linked to the trait of interest would decelerate the process of trait introgression into desired varieties.
C: Breeding procedures to improve plant varieties are generally more successful among sexually compatible species as compared to sexually incompatible species.
D: Co-dominant molecular markers cannot be used for selection of plants with the desired trait.
Which of the above statement(s) is/are INCORRECT?
Given below are some terms in column A and their corresponding properties/related terms in column B
Which one of the following options represents the most appropriate match between all terms of column A and B?Column X Column X A Bulk segregant
analysis(i) QTL analysis of wider genetic diversity using fewer individuals B NILS (ii) Mapping monogenic qualitative trails C Association mapping (iii) Co-dominant markers D SNPs (iv) Repeated backcrossing of F1 to recurrent parent Which one of the following approaches/markers would be typically used for discovering polymorphism between two closely related accessions of a crop plant?
A group of researchers are testing two new agents, M1 and M2 for their efficacy in selecting transgenic plants. When they performed tissue culture experiments using three explants, A, B, and C without Agrobacterium transformation, and selected the regenerated plants on M1 and M2, the following regeneration frequencies were obtained.
Regeneration frequencies (%) in presence of different concentration of agents Explant type M1 conc. (mg/L) M2 conc. (mg/L) 20 60 100 10 15 20 A 44% 21% Nil 8% Nil Nil B 53% 30% 10% Nil Nil Nil C 71% 42% 18% 15% 9% 4% Based on the above data, which one of the following conclusions is INCORRECT?
