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Breeding method for clonal propagation crops, apomixis and clonal selection


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Breeding method for clonal propagation crops, apomixis and clonal selection

  1. 1. Presented by: Hitesh V. Jasani Ph.D. (Plant Molecular Biology and Biotechnology), Principles of Plant Breeding
  2. 2. Asexual reproduction  Multiplication of plants without the fusion of male and female gametes is known asexual reproduction.  Asexual reproduction can occur either  By vegetative plant parts or  By vegetative embryos which develop without sexual fusion.  Asexual reproduction is of two types, 1. Vegetative reproduction. 2. Apomixis.
  3. 3. Vegetative Reproduction  Vegetative reproduction refers to multiplication of plants by means of various vegetative plant parts.  Vegetative reproduction is again of two types : 1. Natural vegetative reproduction. 2. Artificial vegetative reproduction.
  4. 4. Natural vegetative reproduction • In nature, multiplication of certain plants occurs by underground stems, subaerial stems, root and bulbils.  Underground stems: The underground modifications of stem generally serve as strong organs and contain many buds. These buds develop into shoots and produce plant after rooting.  Rhizome : Turmeric, Ginger  Tuber : Potato  Corm : Arvi, Bunda  Bulb : Garlic, Onion
  5. 5. Rhizome : Turmeric (Curcuma domestica), Ginger(Zingiber officinale) Bulb : Garlic (Allium sativum), Onion (A. cepa)
  6. 6. Corm :Bunda (Colocasia antiquorum), Arvi (Colocasia esculenta) Tuber : Potato (Solanum tuberosum)
  7. 7.  Sub-aerial Stems: These modifications include runner, stolon, sucker etc.. Sub-aerial stems are used for the propagation of mint (Mentha sp.), date palm, strawberry, banana etc.. Sucker of Banana Runner of Mint Stolon of Strawberry
  8. 8.  Bulbils: o o o Bulbils are modified forms of flowers that develop into plants directly without formation of seeds. These are vegetative bodies as their development does not involve fertilization and seed formation. They develop into plants when fall on the ground. Bulbils are found in garlic, lily etc.. Bulbils of garlic Bulbils in tiger lily
  9. 9.  Leaves: o This is not very common and It is seen in plants such as Bryophyllum. o It has fleshy leaves and adventitious buds are present at the margins of the leaves. o These buds fall off and grow into new plants.
  10. 10. Artificial vegetative reproduction  Multiplication of plants by vegetative parts through artificial method is known as artificial vegetative reproduction. • Stem cuttings: Sugarcane (Saccharum sp.), Grapes (Vitis vinifera), Roses, etc. • Root cutting: Sweet potato, Citrus, Lemon, etc. • Layering, grafting are used in fruit and ornamental crops.
  11. 11. Cutting: Layering:
  12. 12. Grafting:
  13. 13. Significance Vegetative reproduction has several advantages.  It leads to continuity of same genotype with great precision, because all the progeny have similar genotype and phenotype.  Useful in obtain large number of genetically identical individuals.  Promising genotype can be maintained.  It makes use of desirable bud mutations. Mutants can be directly released as varieties.
  14. 14. Apomixis • Apomixis: Development of seed or embryo without fertilization (sexual fusion). • Obligate Apomixis: A plant which reproduces only by asexual reproduction. • Facultative Apomixis: A plant which has the potential to reproduce either sexually or asexually. Both process may occur simultaneously or one may be predominant.
  15. 15.  Parthenogenesis: Development of embryo from egg cell without fertilization. Haploid : Embryo develops from haploid egg cell. Example - Nicotiana, Maize etc.. o Diploid : Embryo develops from diploid egg cell. Example - many grasses like Taraxacum etc.. o  Apogamy: Development of embryo either from synergids or antipodal cells. Haploid : Embryo develops from haploid synergids or antipodal cells. o Diploid : Embryo develops from diploid synergids or antipodal cells. Example – Allium etc.. o
  16. 16.  Apospory: First diploid cell of ovule laying outside the embryosac develops into another embryosac without reduction. Then develops directly from the diploid egg cell without fertilization. Examples- Parthenium, Crepis etc..  Adventive Embryony: Embryos develop directly from vegetative cells of the ovule, such as nucellus. Adventive embryony occurs in Mango, Citrus etc..
  17. 17. The Ideal Apomictic System 1. All the progeny of plants should be apomictic so that progeny have the same genotype as the maternal parent. 2. The apomictic genotype should preferably be fully male fertile and self-incompatible, and reproduce via pseudogamy. 3. In case of diplospory, chromosomes should not pair or recombine during first meiotic division. which may give rise to variation among the progeny. 4. Apomixis should be dominant over sexual reproduction. Usually, apomixis is governed by two or more genes. 5. Expression of apomixis should be little affected by the environment.
  18. 18. Development of Apomictic Lines Apomictic lines can be developed by the following three different approaches: 1. Gene Transfer from wild species: Genes controlling apomixis can be transferred into a crop species from a related wild species, e.g., from Tripsacum dactyloides into maize, from Pennisetum orientate into pearlmillet. 2. Induced Mutations: This approach aims at developing apomictic forms in normally sexually reproducing species by utilising induced or even spontaneous mutations.
  19. 19. These efforts have focused primarily on sorghum, where two mutant lines showing facultative apospory have been isolated. 3. Isolation of Apomictic Recombinants from Interspecific Crosses: Sometimes apomictic recombinants can be recovered from segregating generations of crosses between two sexually reproducing species. For example, seed formation has been reported in the intergeneric hybrids between T. aestivum and Avena sativa, H. vulgare and T. aestivitm etc…
  20. 20. Role in plant breeding  Rapid production of pure lines Apomixis is an effective means for rapid production of pureline.  Maintenance of superior genotypes Apomixis is useful in maintaining the characteristics of mother plant from generation to generation.  Conservation of heterosis In some cases, hybrid vigour may be conserved for many generation by using recurrent apomixis.
  21. 21. Advantages of Apomixis  Obligate apomixis permits fixation of heterosis in the hybrids. Therefore, farmers can resow the seeds produced by apomictic hybrids generation after generation.  The new hybrid variety could be multiplied from few hybrid seeds in the same manner as purelines. This greatly simplifies hybrid seed production.  Even such parents that flower at different times may be crossed in a greenhouse to obtain few hybrid seeds, which can be used to establish the new hybrid variety.  The nucleus seed of hybrid varieties can be conveniently maintained as hybrid varieties.
  22. 22. Problems in Utilization of Apomixis • Apomixis is a very complicated phenomenon. • Estimation of the level of facultative apomixis, is tedious and time consuming. • In case of facultative apomicts, the proportion of sexual progeny is affected by environmental factors like daylength and temperature. • In the absence of morphological markers linked with apomictic development, maintenance of apomictic stock becomes difficult. • The genetic basis of apomixis is not clear in most cases.
  23. 23. Clonal Selection Clone : Progeny of a single plant obtained by asexual reproduction. Clonal Selection : A procedure of selection superior clones from the mixed population of asexually propagated crops such as sugarcane, potato etc..
  24. 24. Main feature of clones 1. Homologous constitution The progeny of clone is genetically identical and have same genetic constitution. Thus clones are homologous. No genetic variation within a clone. 2. Heterozygosity Asexually propagated crops are heterozygous so clone is also heterozygous. Progeny looks similar phenotypically but is heterozygous. 3. Wider adaptation Clones are more adaptable to environmental variation due to high level of heterozygosity than pure line.
  25. 25. 4. Vigorous growth Clones have hybrid vigour which is conserved due to sexual reproduction. Most of the varieties of sugarcane and potato are hybrids 5. Source of variation There are three sources of variation in a clone. Viz. bud mutations, mechanical mixture, and occasional sexual reproduction. 6. Segregation in F1 When hybridization is done between different clones, segregation occurs in F1 generation. Each F1 plant is potentially a new variety, therefore, selection is practised in F1.
  26. 26. Procedure of Clonal selection First Year Mixture of clones Few to several hundred to thousand superior plants selected.
  27. 27. Second Year Clones from selected Plants i. Clones from the selected plants grown separately ii. Inferior clones are rejected
  28. 28. Third Year Preliminary yield trial i. Preliminary yield trial with standard checks. ii. Selection for quality, disease resistance, etc.. Disease nurseries may be planted iii. Few outstanding clones selected
  29. 29. Fourth Sixth Year Multilocation yield trials i. Mutilocation yield trials with standard checks ii. Best clone Identified for release as a new variety
  30. 30. Seventh Year Seed multiplication i. The best clone is released as a new variety ii. Seed multiplication for distribution begins
  31. 31. Merits      Variety evolved by this method retains all the characters of the parental clones for several years. Varieties are highly uniform like pure lines. They are highly stable because there is no risk of deterioration due to segregation and recombination. Effective method for genetic improvement of asexually propagated crops. Useful in isolation the best genotype from a mixed population of asexually propagated crops. The selection scheme is useful for maintaining the purity of clone.
  32. 32. Demerits This selection method utilizes the variability already present in the population, and it has not been devised to generate variability. Genetic makeup cannot be improved by this method without hybridization. Varieties developed by clonal selection are highly prone to new of a disease.
  33. 33. Achievements  In India, this method successfully used for developing new varieties in potato, sugarcane, banana, citrus and grapes.  Kufri Red and Kufri safed in potato.  Ko 11, ko 22 and Neelam in mango.  Co 541, CoS 510 etc.. In sugarcane.  Pride monthan and High gate in banana.
  34. 34. References • Essentials of Plant Breeding By Phundan Singh. 3rd Ed. pp: 52-55, 128-131. • Plant Breeding By B. D. Singh. 6th Ed. pp: 48-50, 371-373. • Plant Breeding By B. D. Singh. 9th Ed. pp: 55-57, 377-382. • leavingbio.net/vegetativepropagation.htm • Vegetative Propagation | Tutorvista.com • Wikipedia, the free encyclopedia • Breeding methods of clonally propagated crops By Maria Andrade et al., July 2009