Pure-line Theory In Plant Breeding And Genetics:-

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.

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 19^th 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: