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Breeding methods in cross pollinated crops
- 1. Breeding methods in Cross pollinated crops Mass selection - Ear to row method and Progeny selection schemes Submitted by J Venkata Yashwanth TAM/2019-042 ACHARYA N G RANGA AGRICULTURAL UNIVERSITY S.V. Agricultural college, Tirupati Dept. of Genetics and Plant breeding
- 2. Breeding methods in cross pollinated crops Cross pollinated crops are highly heterozygous and heterogeneous They have random mating and maintain deleterious genes in the population More adaptability and flexibility to the environment Heterosis can be fully exploited Inbreeding depression can be seen which makes it difficult for fixing of desirable genes In CP crops genotype of individual is seldom important and breeder tries to increase the frequency of desirable alleles or genes in population
- 3. Methods of breeding Plant introduction Mass and progeny selection Backcross method Heterosis breeding Synthetic breeding Composite breeding Polyploidy breeding Distant hybridization Transgenic breeding
- 4. Population improvement In cross pollinates crops for population improvement three breeding approaches are made Recurrent selection Disruptive mating Biparental mating
- 5. Mass selection Mass selection consists of selecting individuals on the basis of phenotypic superiority and mixing the seeds for using as planting material for next season. It is the earliest method of selection. Mixture of homo and heterozygotes and heterogeneous Further selection of mass selected varieties of cross pollinated crops lead to inbreeding depression Broad genetic base and good adaptability
- 6. Procedure
- 7. There are two kinds of mass selection: Negative mass selection only undesirable plants are removed from field and rest are allowed to grow. usually used for purification in seed production and certification programs Positive mass selection Desired plants are selected and allowed to grow for further Base material here is old varieties or land races
- 8. Merits Can be practiced both in self and cross pollinated crops. The varieties developed through mass selection are more widely adopted than pure lines. It retains considerable variability and hence further improvement is possible in future by selection. Useful for purification of pure line varieties. Improvement of characters governed by few genes with high heritability is possible. Less time consuming and less expensive
- 9. Demerits Varieties are not uniform. Since no progeny test is done, the genotype of the selected plant is not known. Since selection is based on phenotype and no control over pollination the improvement brought about is not permanent. It can not create any new genotype but utilizes existing genetic variability. Characters which are governed by large number of genes with low heritability can not be improved.
- 10. Achievements Cotton : Dharwad American Cotton Groundnut : TMV-1 & TMV-2 Bajra : pusa moti, Baja puri, Jamnagar gaint, AF3 Sorghum : R.S. 1 Rice : SLO 13, MTU-15 Potato : K122
- 11. Progeny selection schemes Ear to row meted and its modification Recurrent selection Simple Recurrent selection Reciprocal Recurrent selection Recurrent selection for GCA and SCA Marker assisted Recurrent selection
- 12. Ear to row method This method was developed by Hopkins in 190 and used more in maize Selection is based on progeny test not based on phenotype Mostly Selection is based on maternal parental Inbreeding depression can be avoided Each selection cycle has generally 2 years
- 13. Procedure
- 15. Merits Selection is based on progeny test not merely on basis of phenotype Inbreeding is possible per each selection cycle Method is easy and simple
- 16. Demerits No control on pollination and selection based on maternal parent Superior progenies re pollinated by both superior and inferior progeny
- 17. Modification of ear to row method First year – several plants are selected based on phenotypes and open pollinated seed is harvested separately Second year – small progeny rows are grown visually evaluated and superior ones are identified. Remaining seed from selected plants is kept separately Third year – remaining seeds are bulked and planted they are allowed to open pollinate and selection cycle can be repeated with same process
- 19. S1 and S2 progeny testing When seeds for progeny testing are obtained by selfing of selected plants rather than open pollination then it is called S1 progeny testing When seeds for progeny testing are obtained by selfing of selected plants for two generations rather than open pollination then it is called S2 progeny testing
- 20. Line breeding A system of breeding in which a number of genotypes with superior performance for several characters are bulked to form a variety Commonly used in animal breeding and in crops for CP crops May involve cross between closely related ones but not continuous Useful to transmit a large proportion of desirable genes from generation to generation Line breeded varieties have to be maintained by open pollination