Principles of Plant Breeding (2+1)

Procedure for transfer of dominant gene

• E.g.Highyielding and widely adapted wheat variety A is susceptible to stem rust another variety B is resistance to stem rust. Stem rust is dominant tosusceptibility.

  1. Hybridization: Variety A is crossed to variety B. Generally variety A should be used as female parent. This would help in identification ofselfed plants.
  2. BC1 Generation: F1 plants are back crossed to variety A. Since all the F1 are heterozygous for rust resistance, selection for rust resistance is not necessary.
  3. First BC1 generation: Half of the plants in BC1 generation are resistant and the remaining half would be susceptible to stem rust. Rust resistant plants are selected and back crossed to variety A.
  4. BC2 to BC 5 generation: Segregation would occur for rust resistance. Rust resistant plants are selected and back crossed to variety A.
  5. BC6 Generation: BC6 plants will have 99 percent genes from variety A Rust resistant plants are selected and selfed, their seeds are harvested separately
  6. BC7Generation: Individual plants progeny from the selfed seeds of the selected plants are grown. Rust resistant plant similar to the plant type of variety A are selected and they are selfed. Seeds are harvested separately.
  7. BC8 Generation: Individual plants progeny are grown. Progenies homozygous for rust resistant and similar to plant type of variety Aare harvested in bulk. Several similar progenies are usually mixed to constitute the new variety.

Yield trials:
It is tested in replicated yield trial along with the variety A as check. All the component character are critically examined a detailed yield tests are not required and variety may be directly released for cultivation.