Principles of Plant Breeding (2+1)

Transfer of a recessive gene

• When Rust resistant isrecessive, all the back crossescannot be made one after the other. For every two subsequent back crosses F2 generation must be grown to identify the rust resistant plants.

  1. Hybridization: The recurrent parent is crossed with the rust resistant donor parent; the recurrent parent is generally used as female parent.
  2. BC1 Generation: F1 plants are back crossed to the recurrent parent.
  3. BC2 Generation: Since rust resistance is recessive, all the plants are rust susceptible. No test for rust resistance and all the plants are self pollinated.
  4. BC3 F2 Generation: Rust resistant plantsare selectedand back crossed to recurrent parent plants which are similar to recurrent parent are selected.
  5. BC4 Generation: There is no rust resistance test. Plants are selected which are resistance to recurrent parent and back crossed.
  6. BC5Generation: There is no disease test. The plants are self pollinated to raise F2. Selection is usually done for the plant type of variety A.
  7. BC6 Generation: Plants are inoculated with rust. Rust resistant plants are selected is back crossed to variety A.
  8. BC7Generation: There is no rust resistance test plants are back crossed to variety A.
  9. BC8 Generation: There is no rust test, plantsare self pollinated to rise F2 generation.

  BC5 Generation:
• Plants are subjected to rest epidemic. Rigid selection is done for rust resistance. And for the characteristics of variety A. Selfed seeds of the selected plants are harvested separately. BC5
Generation:
• Individual plant progeny are grown and subjected to rust epiphytotic. A rigid selection is done for resistant to stem rust and for the characteristics of variety A. Seeds from several rust resistant homogenous progenies are mixed to constitute the new variety.
• Yield test are conducted and released as a variety
• Same procedure also to be practiced in cross pollinated crops