Pure-line theory in plant breeding And genetics:-

Pure-line theory in plant breeding And genetics:-

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  • Pure-line theory in plant breeding And genetics is a progeny which evolves by self pollination from a single homozygous plant.

Pure-line selection:-

  • 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.


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