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Tamil Nadu HSE Second Year Botany study materials
Tamil Nadu HSE Second Year Botany study resources

Tamil Nadu HSE Second Year Botany: Applied Botany: Plant Breeding, Biotechnology and Economic Importance

Tamil Nadu HSE Second Year Botany · Work through your exam, one topic at a time.

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Applied Botany: Plant Breeding, Biotechnology and Economic Importance

This domain asks you to choose a breeding method for a stated objective and to match biotechnological products with their source organism or gene. Objective-plus-method matching is the most examinable skill here.

Core rules

  • Breeding sequence: germplasm collection → evaluation → selection → hybridisation → testing → release of a variety.
  • Methods: mass selection for cross-pollinated crops; pure-line selection for self-pollinated crops; clonal selection for vegetatively propagated crops; pedigree method in hybridisation; mutation breeding with gamma rays or EMS; polyploidy breeding with colchicine, as in triploid seedless watermelon.
  • Hybridisation for disease resistance and yield; the Green Revolution in wheat is associated with Norman Borlaug, and M. S. Swaminathan led its Indian application.
  • Biotechnology: restriction endonucleases and ligase, vectors such as pBR322 and the Ti plasmid of Agrobacterium tumefaciens, transformation, selection, regeneration. Bacillus thuringiensis cry genes give Bt cotton; Golden Rice is biofortified with β-carotene; micropropagation, somatic hybridisation (pomato) and somaclonal variation are standard examples.
  • Economic botany: cereals (rice, wheat, maize), pulses, oilseeds, fibres (cotton, jute), timber (teak, Dalbergia), rubber (Hevea brasiliensis), beverages (tea, coffee) and drugs (Cinchona, Rauwolfia serpentina, Withania).

Worked example

Objective: transfer bollworm resistance into a high-yielding cotton variety. Reasoning: the resistance gene is bacterial, so it must be cloned (cry1Ac), inserted into a Ti plasmid, transferred by Agrobacterium-mediated transformation, and transgenic plants regenerated and tested in the field. Conventional hybridisation cannot move a gene across kingdoms.

Traps that cost marks

Using colchicine as a mutagen, although it induces polyploidy by blocking spindle formation; claiming Bt toxin kills all insects; attributing natural rubber to Ficus; confusing biopiracy with biopatent.