Pure-line theory in plant breeding And genetics:-
- Pure-line theory in plant breeding And genetics is a progeny which evolves by self pollination from a single homozygous plant.
- It is the procedure of isolating pure lines from a mixed population.
Pure-Line theory in plant breeding And genetics:
- Pure-line theory in plant breeding and genetics was given by Wilhelm johannsen by a Danish botanist in 1903.
- He discovered pure-line in French beans (Phaseolus vulgaris).
- He conducted all the experiments for the seed weights in different lots of French or princess beans.
- Beans are self fertilized.
- Homozygous genes affect the seed weight in original mixed seed lot.
- When he did selection within original seed lot it was effective in isolating lines that were genetically different.
- Beans were divided in to groups of one with high seed weight and one with low seed weight.
- But there was a problem,in next generation there was no further use of selected low and high seed weight.
Procedure of Pure-line theory in plant breeding And genetics:-
- Different French beans variteys were selected and gro
- Selected seeds grow as individual plant progenies having different seed size
- Larger seeds & smaller seeds
- Further johannsen grow 19th line having different seed size
- Each and evey seed show mean weight from 0.6426g from pure line 1 to 0.351g of purn line no 19.
- The seed size within aline sowed some variation which will be smaller than the present in original commercial lot.
- Johanssen postulated that each lot was a mixture of pure lines,thus each of 19 line showed a pureline.
From each pure line Wilhelm selected the largest and smallest seeds to rise in the next generation sand grow again and again for next 6 years and selection for next six years will be ineffective.
Finally selection within pureline was ineffective and gave the pure line theory.
Role of pure-line in breeding:
- Superior line is used as variety.
- Pure line can be used as parent in development of new variety of hybridization.
- Used for study the mutation and other biological investigation
Advantages of pure-line theory:
- It has the same genotypes.
- These are attracted and farmers liked them.
- It is easy to identify in seed certification process because of its uniformity.
- Pure-line selection is used in selfpollinated crops.
- It is used to improve local varities or to introduced varities.
See Also: POLYPLOIDY AND ITS NEED AND ROLE IN CROP