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Which of the following would result in somaclonal variation in micropropagated plants?
(P) Propagation by axillary branching in the absence of plant growth regulators
(Q) Cell suspension maintained for five years before induction of somatic embryogenesis
(R) Cullus induction using 20µM 2, 4-Dichlo-rophenoxyacetic acid followed by shoot organogenesis
(S) Shoot organogenesis from an explant in the absence of an intermediate callus phase
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- P, Q
- Q, R
- P, S
- Q, S
Correct Option: B
Somaclonal variation is not restricted to, but is particularly common in, plants regenerated from callus. The variations can be genotypic or phenotypic, which in the latter case can be either genetic or epigenetic in origin. Typical genetic alterations are: changes in chromosome numbers (polyploidy and aneuploidy), chromosome structure (translocations, deletions, insertions and duplications) and DNA sequence (base mutations). Typical epigenetic related events are: gene amplification and gene methylation.
