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:

• 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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See Also: POLYPLOIDY AND ITS NEED AND ROLE IN CROP