Plant Breeding and Genetic Modification

Plant cell walls contain cellulose and pectin as structural components. To obtain naked protoplasts during somatic hybridization, both cellulase (breaks down cellulose) and pectinase (breaks down pectin) are needed to digest the cell wall completely. Amylase (starch), protease (proteins), and lipase (lipids) are not relevant for cell wall digestion.

When culturing anthers, haploid plants come from pollen grains (generative or vegetative cells). Diploid plants result from contamination by diploid cells of the anther wall (2n), which are somatic cells that can grow alongside the intended haploid cultures. The exine is just the pollen outer wall and cannot produce plants.

Young pollen grains are immature male gametophytes that are haploid (n). When anthers are cultured in nutrient medium, pollen grains can divide and form haploid callus tissue, which can regenerate into complete haploid plants - a process called androgenesis. Other tissues mentioned are diploid or somatic.

Option 2 is correct because in gametophytic self-incompatibility, the S₂ pollen would successfully pollinate the S₁S₅ flower, but the S₅ pollen would not.

Bacterial genes for auxin biosynthesis (such as iaaM and iaaH from Pseudomonas syringae) can be inserted into plants to induce parthenocarpy - the development of fruit without fertilization. Auxin is the primary hormone responsible for fruit set and development. Gibberellins and cytokinins are not the primary hormones for this purpose.

Ti (Tumor-inducing) plasmid from Agrobacterium tumefaciens is the most widely used vector for plant genetic engineering. It naturally contains T-DNA that can be transferred into plant genomes and has been modified into a disarmed vector system. The other plasmids (pBR322, pUC18) are E. coli cloning vectors, and ECOR1 is a restriction enzyme.

Electroporation is a physical transformation method where brief electrical pulses create transient pores in the cell membrane, allowing DNA (gene constructs) to enter the cell. It is commonly used for bacterial transformation and protoplast transformation. Options A, B, and C describe unrelated processes - electro-osmosis, water purification, and seed germination stimulation.

Ti plasmid from Agrobacterium tumefaciens is the preferred method for introducing genes into dicot plants because Agrobacterium naturally infects dicots. The T-DNA region of the Ti plasmid integrates into the plant genome. Electroporation, particle acceleration (gene gun), and microinjection are physical methods typically used for monocots which are recalcitrant to Agrobacterium infection.

Gibberellin induces parthenocarpy, i.e. develop seedless fruits from unfertilized pistils.

Mutant selection involves growing plant cell cultures in vitro and screening for mutants with desired traits (like insecticide resistance). Selected mutant cells can then be regenerated into whole plants. Clonal propagation produces genetically identical copies. Cybridization combines cytoplasm from one species with nucleus of another. Protoplast fusion combines whole genomes.

Interspecific somatic hybridization requires: (1) obtaining haploid cells from parental species, (2) removing cellulose walls to isolate protoplasts using enzymes like cellulase and pectinase, (3) fusing protoplasts using PEG or electrofusion, and (4) regenerating the fused hybrid cells into plants through tissue culture. Option A correctly sequences these steps.

Biofortification is the process of breeding crops to increase their nutritional value - specifically higher levels of minerals (iron, zinc), vitamins (vitamin A), proteins, or healthier fats. Micropropagation is rapid vegetative propagation. Somatic hybridization combines genomes of two species. Biomagnification refers to increasing toxin concentration up food chains - unrelated to breeding.

All three statements are true: (A) Plant genomics initially lagged behind animal/microorganism efforts due to larger genome sizes, (B) Researchers can use partial genomic information through ESTs, marker genes, and comparative genomics, and (C) Potato genome sequencing was an active research effort. Since all individual statements are correct, 'All of the above' is the right answer.