Correct option is C
The correct answer is: (3) B and C only
Explanation :Let's carefully evaluate the statements:
Statement A: "Heterosis is always lowest in a cross between two genetically diverse parents." This statement is incorrect. Heterosis (hybrid vigor) is typically highest when two genetically diverse parents are crossed because this combination brings together beneficial genetic traits from both parents.
Statement B: "Cytoplasmic Male Sterility (CMS) may be used in heterosis breeding to eliminate emasculation." This statement is correct. CMS is commonly used in heterosis breeding to prevent self-fertilization and eliminate the need for emasculation, making hybrid seed production more efficient.
Statement C: "The A-line (CMS) and B-line (used for maintenance of CMS) are isogenic lines, differing at only a specific locus." This statement is correct. The A-line contains cytoplasmic male sterility, and the B-line is used for maintaining this sterility. Both lines are isogenic, meaning they are genetically identical except at the specific locus controlling male sterility.
Statement D: "Heterosis can be retained in the F2 generation." This statement is incorrect in the general sense. Heterosis is strongest in the F1 generation, and its effects usually diminish in subsequent generations, including the F2 generation, due to genetic segregation.
Therefore, the correct combination of statements is B and C only.
Information Booster:
CMS is widely used in plant breeding to create sterile male plants, which is essential for hybrid seed production.
The A-line has the CMS trait, while the B-line maintains the CMS, ensuring successful hybridization without the need for emasculation.
Heterosis is maximized in the F1 generation, where hybrid vigor results in superior traits like increased yield or disease resistance.
Isogenic lines like the A-line and B-line are genetically identical except for the CMS locus, which is crucial for breeding hybrids.
Cytoplasmic male sterility simplifies hybridization, making it an important technique in many crops like maize, tomato, and sunflower.
The concept of heterosis retention in F2 is not commonly observed as the effects of hybrid vigor usually diminish in subsequent generations due to genetic segregation.
