Breeding and hybrid production — Which breeding method uses enzymatic/chemical removal of cell walls and fusion of protoplasts from two sexually incompatible plant species?
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AMass selection
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BProtoplast fusion
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CTransformation (gene transfer using vectors or direct DNA delivery)
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DTranspiration (physiological water loss)
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EMarker-assisted selection
Answer
Correct Answer: Protoplast fusion
Explanation
Introduction / Context:Protoplast fusion enables somatic hybridization between distantly related plants that cannot cross sexually. By removing cell walls, plasma membranes can be brought into close contact and fused to combine nuclear and cytoplasmic genomes.
Given Data / Assumptions:
- Cell walls are removed using cellulases/pectinases.
- Fusion is induced by polyethylene glycol (PEG) and/or electric fields (electrofusion).
- Somatic hybrids and cybrids can be regenerated via tissue culture.
Concept / Approach:The key distinction is wall removal plus fusion, which is unique to protoplast fusion. Mass selection and marker-assisted selection do not involve cell wall removal; transformation introduces DNA but does not fuse whole cells.
Step-by-Step Solution:
Generate viable protoplasts from two species.Induce fusion (PEG or electrofusion).Regenerate hybrid callus and select for hybrids.Verification / Alternative check:Hybrid cells can be confirmed by cytological markers, selectable markers, or organelle DNA profiling.
Why Other Options Are Wrong:
a,e) Selection strategies, not fusion methods.c) Transformation alters genomes but does not fuse cells.d) Irrelevant to breeding.Common Pitfalls:Losing viability due to osmotic shock; careful stabilization and plating density are critical.
Final Answer:Protoplast fusion.