BREEDING METHODS FOR ASEXUALLY PROPAGATED SPECIES

Dr. NAVEENKUMAR K.L
Assistant Professor

1. Dr. NAVEENKUMAR K.L Assistant Professor Dept. Of Genetics and Plant Breeding UAHS Shivamogga BREEDING METHODS FOR ASEXUALLY PROPAGATED SPECIES

2. Mode of reproduction Asexual reproduction Sexual reproduction

3. Main reasons of asexual reproduction are Reduced flowering and seed set: sugarcane, potato Non flowering in many species: Ginger, Garlic, betel To avoid inbreeding depression in certain crops: Banana, sugarcane Apomixes in some species: Banana, Grape

4. II. Vegetative propagation II.1. Natural vegetative propagation methods Rhizome: Eg : Ginger, Turmeric, Lotus Tuber: Eg : Potato Bulb: Eg : Taro, Gladiolus, Saffron Bulbil: Eg : Agave Americana , Dioscorea Sub-aerial modification of stems Runner : Wood sorrel, Straw berry, Water lettuce Stolons : Jasmine, Tecuma grandiflora Sucker: Like the stolons lateral branch developing from underground part of the stem. (Bamboo, Chrysanthimum , Banana ) Modified roots Normal roots of wood apple and citrus are used for propagation. Some modified roots such as tuberous roots in sweet potato; fasciculated roots in Dahlia and Asparagus can give new individuals . II.2. Artificial vegetative propagation methods cuttings (Sugarcane) air layer (Lemons, Grapevine and Jasmine ) gootee layering (Lemon and Orange) grafting ( Sapota , Mango) budding (Rose )

5. 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.

6. Apomixes

7. 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 . These efforts have focused primarily on sorghum, where two mutant lines showing facultative apospory have been isolated.

8. 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…

9. Methods of Breeding Asexually Propagated Species Plant Introduction Clonal selection Mass selection Heterosis breeding Mutation breeding Polyploidy breeding Distant hybridization Transgenic breeding

10. 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 is referred to as Clonal Selection. In asexually propagated vegetable crops, several cultivars have been developed by clonal selection . For e.g.- in potato, kufri red is a clonal selection from a cultivar Darjeeling red round kufri safed from cultivar phulwa .

11. Main feature of clones Homologous constitution The progeny of clone is genetically identical and have same genetic constitution . 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 .

12. 4 . Vigorous growth Clones have hybrid vigour which is conserved due to sexual reproduction . ex: 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 practiced in F1 .

13. Procedure

14. 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.

15. 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.

16. Achievements In India, this method successfully used for developing new varieties in potato, sugarcane, banana, citrus & grapes. potato - Kufri Red and Kufri safed Mango- Ko 11, ko 22 and Neelam sugarcane- Co 541, CoS 510 banana- Pride monthan and High gate

17. Clonal Hybridization Clonal crops are generally improved by crossing two or more desirable clones, followed by selection in the F1 progeny and in the subsequent clonal generations. Once the F1 has been produced, the breeding procedure is essentially the same as clonal selection. The improvement through hybridization involves the following three steps: 1 . Selection of parents, 2 . Production of F1 progeny, 3 . Selection of superior cones

18. Achievements Potato- Kufri Alankar , kufri ashoka , kufri surya sugarcane- Co1148, Co-1158,Co-975