Correct Option (b):
Cytoplasmic male sterility (CMS) is a genetic phenomenon where plants are unable to produce functional pollen. This maternally inherited trait is extensively utilized in hybrid seed production, including the development of certain transgenic varieties, to facilitate cross-pollination and prevent self-pollination, thereby ensuring the desired genetic combinations.
Gene silencing is a molecular biology technique that involves inhibiting the expression of specific genes. It is a crucial tool in genetic engineering for creating transgenic crops with improved traits, such as enhanced resistance to pests, diseases (e.g., viruses), or herbicides, by precisely 'switching off' target genes or pathways.
Incorrect Options:
Budding and grafting are conventional horticultural methods of asexual plant propagation. They involve joining parts of two plants (a scion and a rootstock) to grow as a single plant, primarily to combine desirable traits or to propagate plants that do not root easily. These techniques do not involve the alteration of the plant's genetic material through the introduction of foreign DNA and are therefore not used to create transgenic crops.
Options 1 only and 1 and 3 are incorrect because budding and grafting are traditional propagation methods and not genetic engineering techniques employed for developing transgenic crops.
Option None is incorrect as both cytoplasmic male sterility and gene silencing are indeed significant techniques used in the creation and development of transgenic crops.