Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development.

1. AN INTRODUCTION TO APOMIXIS
Vikas Kumar
M.Sc (G&PB)
Chaudhary Charan Singh University

2. INTRODUCTION
While parthenocarpy is the formation of fruit without
fertilization, apomixis is the formation of seeds without fertilization. In
a natural flow of biological processes, pollination is the first step in the
formation of a fruit and seed. The subsequent steps include cell
divisions and fertilization.
But in this case there is no mieotic division and
fertilization of the gametes to from a zygote. The entire process is cut
short and seeed formation occurs by the way of apomixis.

3. APOMIXIS : DEFINITION
Apomixis is derived from two Greek words “apo” means “away from”
and “mixis” means “act of mixing.”
Dicovered by Leuwen hock in 1719 in Citrus seeds.
Apomixis may be defined in following ways:-
“Apomixis is a type of reproduction in which sexual organs
of related structures take part but seeds are formed without union of
gametes.”
Apomixis refers to:-
“Development of embryo without sexual fusion.”

4. Mechanisms
of sexual and
apomictic
seed
development

5. Types of
Apomixis
1.
Gametophytic
Apomixis
2.
Sporophytic
Apomixis

6. 1. GAMETOPHYTIC APOMIXIS
If the unfertilized cells give rise to a mega gametophyte, than it is refers
to Gametophytic Apomixis.
Apospory:- It is the development of embryo sac from vegetative or non-
reproductive cells of the ovule, without meiosis and spores.
Diplospory:- In this method embryo sac is developed from the
microspores. It occurs diploid due to absence of meiosis, but it may be
haploid.
Androgenesis:- The embryo sac originates from generative nucleus of
pollen tube cells the most common mechanism of apomixis in higher
plants characterized by the presence of multiple embryo sacs.

7. 2. SPOROPHYTIC APOMIXIS
If the unfertilized cells give rise to an embryo.
Haploid Parthenogenesis:- Embryo developed from egg cell.
Haploid apogamy(Pseudogamy):- Embryo developed from
synergids or antipodal cells.
Adventitious Embrony (Sporophytic Budding):- Embryo
directly develop from nucellus or integuments (no production of
embryo sac) e.g. Mango, Citrus.

8. TYPES OF APOMIXIS BASED ON OCCURANCE
Apomixis
1.
Recurrent
Apomixis
2. Non-
recurrent
Apomixis
3.
Adventive
Embryony
Source:- ecoursesonline.iasri.res.in

9. 1. RECURRENT APOMIXIS
An embryo sac develop from the megaspore
mother cell where meiosis is disturbed or from some adjoining
cell. Consequently, the egg cell is diploid. The embryo
subsequently develops directly from the diploid egg cell without
fertilization. E.g. Crepis, Taraxacm, Poa(Blue Grass) without the
stimulus of pollination.

10. 2. NON-RECURRENT APOMIXIS
If an embryo aries directly from normal egg cell (n)
without fertilization. Since an egg cell is haploid, the
resulting embryo will also be haploid.
OR
If an embryo develop from any cell of embryo sac is
known as Non-recurrent Apomixis (haploid cell).

11. 3. ADVENTIVE EMBRYONY
Embryos aries from a cell or a group of cells either in
the nucellus or in the integuments is known as Adventive embryony,
e.g. in Oranges and roses.
Embryo within the embryo sac may also develop
simultaneously, thus giving rise to poly-embryony condition, as in
citrus and optunia.

12. ROLE OF APOMIXIS IN PLANT BREEDING
Rapid production of pure lines
Apomixis is an effective means for rapid production of pure line.
Maintenance of superior genotypes
Apomixis is useful in maintaining the characteristics of mother
plant from generation to generations.
Conservation of heterosis
In some cases, hybrid vigour may be conserved for many
generations by using recurrent apomixis.

13. USES/APPLICATIONS OF APOMIXIS IN
PLANT BREEDING
Rapid multiplication of genetically uniform individuals can be
achieved without risk of segregation.
Heterosis or hybrid vigour can permanently be fixed in crop
plants, thus no problem for recurring seed production of F1 hybrids.
Efficient exploitation of maternal effect, if present, is possible from
generation to generation.
Homozygous inbred lines, as in corn., can be rapidly developed as
they produce sectors of diploid tissues and occasional fertile
gametes and seeds.
Source:- ecoursesonline.iasri.res.in

14. ADVANTAGES OF APOMIXIS
The nucleus seed of hybrid varieties can be conveniently maintained
as hybrid varieties.
The new hybrid variety could be multiplied from few hybrid seeds
in the same manner as pureline. This greatly simplifies hybrid seed
production.
Obligate apomixis permits fixation of heterosis in the hybrids.
Therefore farmers can resow the seeds by apomictic hybrids
generation after generation.
Even such parents that flower at different times may be crossed in a
green house to obtain few hybrids.

15. PROBLEMS IN UTILIZATION OF APOMIXIS
1) Apomixis is a very complicated process.
2) Estimation of the level of facultative apomixis, is tedious and time
consuming.
3) In case of facultative apomixis, the proportion of sexual progeny is
affected by environmental factors like day length and temperature.
4) In the absence of morphological markers linked with apomixis
development, maintenance of apomixis stock becomes difficult.
5) The genetic basis of apomixis is not clear in most cases.