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PLANT BREEDING AGR 3204

PLANT BREEDING AGR 3204. Plant Reproduction System. Plant Reproduction System. The reproduction mechanism of a particular plant species or the way it reproduces determines its genetic characteristics the breeding approach. 1. Sexual Reproduction.

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PLANT BREEDING AGR 3204

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  1. PLANT BREEDINGAGR 3204 Plant Reproduction System

  2. Plant Reproduction System • The reproduction mechanism of a particular plant species or the way it reproduces determines • its genetic characteristics • the breeding approach.

  3. 1. Sexual Reproduction • Using sex organs to form next generation / to produce seeds.

  4. 1. Sexual reproduction (cont.) Important steps: • Production of gametes (gametogenesis) • Pollination – Transfer of pollen from anther (male organ) to the stigma (female organ). • Fertilization – The union of male and female gametes to produce new genotypes.

  5. POLLINATION • Transfer of pollen from anther (male organ) to the stigma (female organ). • Two kinds of pollination, • Self pollination • Cross pollination

  6. Self Pollination • Transfer of pollen from anther to stigma of the same flower / plant

  7. Self pollination • Natural mechanisms that encourages self pollination: • Cleistogamy • Pollination happens when flower is still closed. Example: Rice

  8. Self Pollination (cont.) • Stigma protected by anther • Anthesis and pollination occur instantaneously once the flower blooms. • Many pollen are produced, covering the stigma, hence preventing pollination by pollen from outside. Example: lime, tomato and chilli Chilli flower

  9. Self pollination (cont.) 3. Stigma and anther protected by other parts of flower. • Male (stamen) and female (pistil) organs covered by keel, i.e. two fused petals. • Example: Leguminosae family, sub-family Papilionoideae.

  10. Cross Pollination • Transfer of pollen from anther to stigma of flower of different plant.

  11. Cross Pollination(cont.) • Natural mechanisms to promote cross pollination: • Dieocious • Male and female flowers are formed on different plants. • Have male and female plants. • Example: Papaya, salak Male salak flower Female salak flower

  12. Cross Pollination(cont.) 2. Monoecious • Male and female flowers are in separate positions on the same plant but mature at slightly different times. • Example: Oil palm, corn and rubber.

  13. Cross Pollination(cont.) 3. Dichogamy Anther and stigma from hemaphrodite flower or flower of monoecious plant mature at different times. • Protogyne Stigma (female flower) matures before anther (male flower). Example: Potato, cassava and cashew. Protogyne: Potato flower

  14. Cross Pollination(cont.) 3. Dichogamy (cont.) • Protandry Anther (male flower) matures before stigma (female flower). Example: Starfruit and rubber. Protandry: Starfruitflower

  15. Cross Pollination(cont.) 4. Self-incompatibility Pollens are unable to fertilize ovule (female gamete) of the same flower/plant due to genetic factor (self incompatibility gene) Example: Potato, passion fruit and starfruit.

  16. Cross pollination(cont.) • In some species, there are more than one mechanism to promote cross pollination: • Rubber and corn: monoecious and protandry. • Potato, Sweet potato: Self-incompatibility and protogyne • Starfruit & passion fruit: Self-incompatibility and protandry

  17. Methods to determine modes of pollination 1. Identify flower formation system. 2. Isolate plants. No fruit/seed  cross pollinated Fruit set/seed set  self pollinated and possibly cross pollinated 3. Selfing. To observe the effects of inbreeding. Present  cross pollinated. Absent / minimal  self pollinated.

  18. 2. Asexual Reproduction • Does not involve sex or union of male and female gametes. Mechanisms:- • Vegetative reproduction • Apomixis

  19. Vegetative Reproduction • Stem/branch/root cuttings  e.g. cassava • Grafting  e.g. rubber, rambutan & durian • Rhizome  e.g. tumeric & ginger • Stolon e.g. grass • Tuber  e.g. potato & sweet potato • Tiller  e.g. pineapple , sugarcane & banana

  20. apomixis • Formation of seeds without union of gametes, i.e. fertilization.

  21. Apomixis (cont.) • Apogamy – Embryo formation from synergids or antipodals

  22. Apomixis (cont.) • AposporyEmbryo develops from somatic cell such as nucellus and integument. • DiplosporyEmbryo develops from megasporocyte. • Adventitious embryo Embryo develops directly from nucellus and integument cells without involving embryo sac cells. • Parthenogenesis Embryo develops from unfertilized eggs.

  23. Apomixis (cont.) • Obligate apomixis • Apomixis reproduction is the main method of reproduction. • Example: mangosteen

  24. Facultative apomixis • Both apomixis and sexual reproduction occur. • Example: Guinea grass (Panicum maximum), Citrus sp.

  25. Characteristics of cross pollinated, self pollinated and asexual plants

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