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Apomixis–Definition,Types and practical applications.pptx

1) Apomixis is a form of asexual reproduction in plants where seeds are produced without fertilization. Embryos develop parthenogenetically from the egg, central cells, or other cells of the ovule or nucellus. 2) There are two main types of apomixis - facultative, where sexual reproduction can also occur, and obligate, where sexual reproduction is absent. The four mechanisms of apomixis are recurrent apomixis, non-recurrent apomixis, adventitious embryony, and vegetative apomixis. 3) Apomixis has practical applications for plant breeding as it allows for the rapid production of uniform lines

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APOMIXIS–DEFINITION,TYPES AND PRACTICAL APPLICATIONS Yogesh Sharma Assistant Professor Department of Botany GDC Akhnoor
“APO” (away from) and “MIXIS” (act of mixing or mingling). Discovered by Leuwenhoek as early as 1719 in Citrus seeds. Definition “The process of development of diploid embryos without fertilization.” Or “Apomixis is a form of asexual reproduction that occurs via seeds, in which embryos develop without fertilization.” Or “Apomixis is a type of reproduction in which sexual organs of related structures take part but seeds are formed without union of gametes.”
Fig-Initiation and progression of Apomitic Mechanisms relative to events in the sexual life cycle of Angiosperms. Source- http://www.plantcell.org/content/plantcell/16/suppl_1/S228/F1.large.jpg?wi dth=800&height=600&carousel=1
In apomictic species, sexual reproduction is either suppressed or absent.Therefore,based on the occurrence of Sexual reproduction, Apomixis is of two types:- Facultative Apomixis Obligate Apomixis Types of Apomixis: Maheshwari (1950) classified apomixis into four groups: (a)Recurrent Apomixis : Embryo sac develop without meiosis from diploid cell. Diplospory : Embryo sac develop from MMC. Apospory : Embryo sac develop from any vegetative cell of ovule, than embryo is developed from diploid egg cell. E.g. Poa, Taraxacum and Allium without the stimulus of pollination Parthenium, Rubus, Malus (apple) with the stimulus of pollination.
(b) Non-Recurrent Apomixis: Embryo develop from any cell of embryo sac (haploid cell)  Haploid parthenogenesis : Embryo develop from egg cell  Haploid Apogamy(Pseudogamy): Embryo developed from synergids or antipodal cells. E.g. Solanum nigrum and Lilium species (c)Adventitious Embryony or Nucellar Embryony:- Embryo directly develop from nucellus or integuments(no production of embryosac). It occurs in many plant species but is most prominent in tropical and sub-tropical tree species, like citrus and mango. (d) Vegetative apomixis or bulbils: E.g. Allum, Agave, Poa and Diascorea and some grasses
PRACTICAL IMPORTANCE:  Rapid production of pure lines (Genetically uniform individuals)  Heterosis or Hybrid vigour can permanently be fixed in crop plants , thus no problem for recurring seed production of F1 hybrids.  Adventive embryos are better clones than cuttings.  Embryos formed through apomixis are generally free from infections.E.g Adventive embryony well known in Citrus, is being used in the Production of root stock and virus free section material.
Apomixis–Definition,Types and practical applications.pptx