Choosing a cell-based strategy To obtain a plant line that is resistant to a specific insecticide chemical, which cell/tissue culture approach is generally most effective?

Introduction / Context:
When the goal is resistance to a specific chemical (e.g., an insecticide used in crop storage or production), plant breeders can use cell culture to select rare, spontaneously resistant variants. This strategy differs from traits introgressed via hybridization or added by transgenics.

Given Data / Assumptions:

• The chemical is an insecticide applied to the plant or its environment.
• We want plant cells that survive otherwise inhibitory concentrations.
• Plant cell cultures exhibit somaclonal variation, generating selectable mutants.

Concept / Approach:
Expose callus or cell suspensions to the insecticide at gradually increasing doses. Surviving cells likely carry mutations permitting tolerance or altered uptake/target sensitivity. Regenerate whole plants from these resistant lines and screen for stable field expression.

Step-by-Step Solution:

Verification / Alternative check:
Similar approaches have yielded herbicide-, salt-, and fungal-toxin–tolerant cell lines using in vitro selection, validating the method for chemical resistance traits.

Why Other Options Are Wrong:

• Clonal propagation just multiplies existing genotypes; it does not create new resistance.
• Cybridization affects cytoplasmic genomes (mitochondria/chloroplasts), not typically target-site resistance to synthetic insecticides.
• Protoplast fusion combines nuclear genomes but is random and not targeted to a specific chemical resistance unless one parent already has it.
• Meristem culture removes viruses; it does not generate chemical resistance.

Common Pitfalls:
Confusing insect resistance to pests (e.g., Bt) with resistance to an insecticide chemical; the former is typically transgenic, the latter often uses mutation/selection.

Final Answer:
Mutant selection in vitro (selection on the insecticide)