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. Based on the above data, which one of the following conclusions is INCORRECT?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%
Use of M1 with explant type B is the most ideal combination for selection of transformants.
The question asks us to analyze the provided data on regeneration frequencies of untransformed explants in the presence of two selection agents, M1 and M2, and identify the incorrect conclusion among the given options. Selection agents in plant tissue culture are used to kill or inhibit the growth of untransformed cells while allowing transformed cells (which usually contain a resistance gene) to survive and regenerate. Therefore, for effective selection, the regeneration frequency of untransformed explants in the presence of the selection agent should be as low as possible, ideally zero.
Regeneration Data Analysis
Let's first look at the data presented in the table:
| Explant type | M1 conc. (mg/L) | M1 conc. (mg/L) | M1 conc. (mg/L) | M2 conc. (mg/L) | M2 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% |
The table shows the regeneration frequency of three different explants (A, B, and C) at various concentrations of agents M1 and M2. 'Nil' indicates 0% regeneration.
Evaluating Selection Agent Efficacy
A stronger selection agent at a given concentration will result in lower regeneration frequency of untransformed cells. An ideal combination of explant and selection agent/concentration for selecting transformants would show minimal to zero regeneration of untransformed cells.
Analysis of Options
Let's evaluate each conclusion based on the data:
-
M2 is a stronger selection agent than M1 for explant types A and B.
For explant A:
- With M1, regeneration is Nil (0%) at 100 mg/L.
- With M2, regeneration is Nil (0%) at 15 mg/L.
M2 achieves 0% regeneration at a much lower concentration than M1 for explant A.
For explant B:
- With M1, regeneration is 10% at 100 mg/L.
- With M2, regeneration is Nil (0%) at 10 mg/L (and higher concentrations).
M2 achieves 0% regeneration at a very low concentration for explant B, while M1 still allows 10% regeneration even at 100 mg/L. Thus, M2 is indeed stronger than M1 for both explant types A and B. This conclusion is CORRECT.
-
A concentration of 100 mg/L of M1 and 15 mg/L of M2 can be used for selection of transformed cells using explant type A.
For explant A at 100 mg/L M1, the regeneration frequency is Nil (0%).
For explant A at 15 mg/L M2, the regeneration frequency is Nil (0%).
Since untransformed cells do not regenerate at these concentrations for explant A, these concentrations could potentially be used for selecting transformed cells, assuming transformed cells are resistant. This conclusion is CORRECT.
-
Among the three explants, type C is least suitable at the tested concentrations of M1 and M2
Least suitable for selection means untransformed cells regenerate significantly even in the presence of the agent, making it difficult to distinguish transformed from untransformed cells. Let's compare the regeneration frequencies at high concentrations:
- Explant A: 0% regeneration at 100 mg/L M1 and 15 mg/L M2.
- Explant B: 10% regeneration at 100 mg/L M1 and 0% regeneration at 10 mg/L M2.
- Explant C: 18% regeneration at 100 mg/L M1 and 4% regeneration at 20 mg/L M2.
Explant C shows the highest regeneration frequencies across most concentrations compared to A and B, particularly at the highest tested levels of both agents. This indicates that untransformed type C cells are the least sensitive to the inhibitory effects of M1 and M2 at the tested concentrations. Therefore, type C is the least suitable for selection under these conditions. This conclusion is CORRECT.
-
Use of M1 with explant type B is the most ideal combination for selection of transformants.
An ideal combination should efficiently suppress the regeneration of untransformed cells. For explant B with M1, the regeneration frequency is 10% at 100 mg/L.
Let's compare this to other combinations:
- Explant B with M2: 0% regeneration at 10 mg/L. This suppresses untransformed regeneration completely.
- Explant A with M1: 0% regeneration at 100 mg/L.
- Explant A with M2: 0% regeneration at 15 mg/L.
Combinations like Explant B with M2 (at ≥ 10 mg/L), Explant A with M1 (at 100 mg/L), and Explant A with M2 (at ≥ 15 mg/L) all result in 0% regeneration of untransformed cells, which is more ideal than 10% regeneration. Therefore, using M1 with explant type B is clearly not the "most ideal" combination for selection. This conclusion is INCORRECT.
Based on the analysis, the conclusion that is INCORRECT is the statement that the use of M1 with explant type B is the most ideal combination for selection of transformants.
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?
Which one of the following options best represents the sequence of events leading to the phenomenon of introgression?
