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Pure line selection and Progeny test
Pureline selection involves the progeny of single homozygous self-pollinated crops, leading to non-heritable variation due to environmental factors. It is primarily used to improve self-pollinated crops, with a systematic process of selection, isolation, testing, and release over several years. The method is advantageous for its efficiency and uniformity but has limitations regarding adaptability and genetic diversity.
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Pure line selection and Progeny test
- 1. Pureline selection and progenytest Dr. Rajendragouda Patil Assistant professor Genetics and Plant Breeding School of Agricultural Sciences and Technology (SAST), NMIMS, MPTP Shirpur
- 2. Pureline selection • Itis the progeny of single homozygous self pollinated crop species • All the plants in the Pureline has same genotype. • The phenotypic differences within a Pureline is due to environment. Hence variation within a Pureline is not heritable – selection is not effective • The concept was given by Johannsen (1903) on the bases of his studies with “Princes” variety of French bean (Phaseolus vulgaris). Johannsen
- 3. 1 43 562 7 109 11 128 1413 15 16 17 1918 640 350 Princes variety French Bean seed lot Seed classification based on size and test weight
- 4. F1 F2 F3 F6 640 mg 640 mg F1 F2 F3 F6 350mg 350 mg 1st Line 19th Line
- 5. F1 F2 F3 F6 475 mg 13th Line Case-1 450mg F1 F2 F3 F6 450 mg F1 F2 F3 F6 451 mg F1 F2 F3 F6 458 mg 100 mg 200 mg 300 mg 400 mg 400 mg
- 6. F1 F2 F3 F6 680 mg 1st Line 640mg F1 F2 F3 F6 690 mg Case-2
- 7. • Parent offspringcorrelation within line # 13 was =-0.018 ± 0.038 (~Zero) • Correlation within seed lot was = 0.336 ± 0.008 • When correlation is zero (non significant)- variation is non heritable • When correlation is not zero (significant)- variation is heritable i.e variation has genetic basis. Case-3 Parent offspring correlation
- 8. 1. Selection iseffective in population since it contains mixture of several lines/ genotypes 2. Selection is ineffective in Pureline, since it is a progeny of single, self fertilized homozygous individual Two main conclusions of Johannsen’s experiments are
- 9. Genetic Basis ofPureline Number of Generations Frequency % Frequency % AA Aa aa Homozygosity Heterozygosity 1 0 100 0 0 100 2 25 50 25 50 50 3 37.5 25 37.5 75 25 4 43.75 12.5 43.75 87.5 12.5 5 46.875 6.25 46.875 93.73 6.25 6 48.437 3.125 48.437 96.874 3.125 7 49.218 1.562 49.218 98.436 1.562 8 49.608 0.781 49.608 99.216 0.781 9 49.803 0.39 49.803 99.606 0.39
- 10. • Self pollinationincreases the homozygosity with corresponding decreases in the heterozygosity. • Suppose an individual heterozygous for a single gene (Aa) and the successive generations derived from it are subjected to self- pollination. • Every generation of self-pollination will reduce the frequency of heterozygote Aa to 50 per cent of that in the previous generation • There is a corresponding increase in the frequency of the two homozygotes AA and
- 11. • aa. Asa result, after 10 generations of selfing, virtually all the plants in the population would be homozygous, i.e., AA and aa. • three genotypes AA, Aa and aa have equal survival, On the other hand, the frequency of heterozygote Aa would be only 0.097 per cent, which is negligible. • If there is unequal survival, it may increase or decrease the rate at which homozygosity is achieved. • If Aa is favored, the rate of increase in homozygosity would be lower than expected.
- 12. Pureline selection • Itis mainly used for the improvement of self pollinated crops. • Present day varieties of self pollinated crops are purelines. • It is mainly used to improve • Local varieties • Old purelines • Introduced varieties
- 13. Procedure of PurelineSelection 1. Selection of purelines from heterogeneous population (1st yr)-Selection 2. Isolation of purelines by individual plant selection (2nd yr)- Evaluation 3. Testing of selected purelines in the yield trials (3rd -5th yr)- Yield trials 4. Release of pureline as variety (6th -8th yr)- Multiplication and distribution
- 14. Advantages of PurelineSelection • Easy and cheap method of crop improvement • Rapid method, lines are usually genetically fixed and yield trials can be immediately conducted. • Plants in such variety react in similar fashion to environmental conditions, means they are uniform in performance and at the same time in appearance too. • Maximum possible improvement over the original variety can be achieved • Useful in improving low heritability traits as selection is based on progeny performance
- 15. Disadvantages of PurelineSelection • Purelines have poor adaptability due to narrow genetic base, just opposite to mass selected variety • Superior genotypes can only be isolated from the mixed population. This selection is powerless to bring changes in hereditary factors i.e. to develop new genotype. • Mostly popular or in fact limited to self pollinated spp. only • Time and space consuming • Difficult to identify the small differences between the cultivars/lines
- 16. Achievements • Rice :Mtu-1, Mtu-3, Mtu-7, Bcp-1, Adt-1, 3, 5, and 10 • Sorghum : G 1 & 2, M 1 & 2, OO 1, 4 & 5, • Groundnut : TMV 3, 4, 7, 8 and Kadiri 71-1 • Redgram : TM-1, ST-1 • Chillies : G1 & G2 • Ragi : AKP 1 to 7
- 17. Progeny test • Evaluationof the worth of plants on the basis of performance of their progenies is known as progeny test. • developed by “Louis de vilmorin” and so it is also known as the “vilmorin Isolation principle”. • Functions of Progeny test: • Determines the breeding behavior of a plant i.e. whether it is homozygous or heterozygous. • Whether the character for which the plant was selected is heritable i.e. is due to genotype or not.
- 18. Features • The selectionof superior plants based on the progeny performance • Commonly used in the cross pollinated crops and often cross pollinated crops. • In cross pollinated crops three types of material viz., 1. Open pollinated seeds 2. Self seeds 3. Top cross or test cross seeds • 10-15 seeds of each selected plants are grown for progeny test • Test conducted in replicated trials to get reliable results. • Superior progenies for the traits are bulked together to produce next generation • The ear to row selection is used in maize is a simple form of progeny selection • Line breeding: composition/mixing of several superior performing genotypes for several traits to get one good variety is known as line breeding.