- Johannsen developed the pure line theory while working with princess beans in 1901. He established 19 pure lines through individual plant selection and followed with selection among the pure lines. - Johannsen concluded that continuous inbreeding leads to homozygosity, variation within a pure line is due to environment only, and selection within a pure line is not effective because all plants have the same genotype. - A pure line is the progeny of a single homozygous, self-pollinated plant. Pure line selection involves evaluating individual plant progeny from a self-pollinated crop to release the best as a pure line variety.

1. SAM HIGGIN BOTTOM UNIVERSITY OF AGRICULTURE,
TECHNOLOGY & SCIENCES, NAINI, ALLAHABAD
DEPARTMENT OF PLANT BREEDING AND GENETICS
TOPIC: PURE LINE THEORY AND PURE LINE SELECTION
PRESENTED BY
P. NIKHIL
19MSCGPB177
SUBMITTED TO:
Dr.B.G.SURESH
DEPT OF GENETICS AND PLANT BREEDING

2. • Started experiments in 1901.Established 19 pure lines by selection of
individual beans from the mixed seed lot of 8kg.(named those as A,B,...,T)
• Followed selection among these purelines too and selected the smallest and
largest beans (seeds).planted those selected seeds.
Pure LineTheory
Johannsen developed concept of pure line while working with princess bean (
Phaseolus vulgaris nana).Princess bean exhibits self -pollination
Procedure:

3. Johannsen’s theory and conclusions:
• Continuous inbreeding (selfing) leads to homozygosity.
• Variation with in a pure line results from environment only.
• Selection with in pure line is not effective because all the plants in a pure line have
some genotype.
• Selection in the original population is effective because the plants have genetic
variation.

4. PURE LINE SELECTION
INTRODUCTION:
• A pure line is the progeny of a single homozygous, self pollinated plants.
• In pre line selection a large number of plants are selected from a self
pollinated crop and harvested individually; individual plants progeny from
them are evaluated and the best progeny is released as a pure line variety.
• All the individuals within a pure line have identical genotype and any
variation present within a pure line solely due to environment.

5. Characteristics of Purelines:
• All the plants within a Pureline have the same genotype as the
plant from which the pureline was derived since the parent plant
was homozygous and self-fertilized.
• Variation present within a pureline is due to the environment and
non heritable.
• Purelines become genetically variable with time due to
mechanical mixture, natural hybridization and mutations.

6. Uses of Purelines
• As a variety
• As Parents in hybridization programme.
• In studies on mutation
• Pure lines are used for studying mutations and other biological investigations
such as medicine, immunology, physiology, and biochemistry.

7. Application of Pureline selection
• Improvement of local varieties.
• Selection in introduced varieties.
• Improvement of old Pureline varieties.
• Selection for a new characteristic in a pureline.

8. Pure line selection Procedure:

9. Advantages of Pureline Selection
• It achieves the maximum possible improvement over the original variety.
• Pureline varieties are extremely uniform; they are therefore preferred by
farmers and consumers to a less uniform variety developed through mass
selection.
• Due to extreme uniformity, the variety is easily identified in seed
certification programmes.

10. Disadvantages of Pureline Selection
• The varieties developed through Pureline selection generally do not have the wide
adaptation and stability in the production possessed by the local varieties from
which they are developed.
• Pureline selection requires more time, space and expensive yield trials than mass
selection.
• The improvement is dependent on the genetic variation present in the original
population.
• The breeder has to devote more time to pureline selection than to mass selection.

11. THANKYOU