Natural vegetative, artificial vegetative, Apomixis

1. Sub.:- Fundamentals of Plant Breeding
Course No. :- APB- 5211
Credit hours:- 3(2+1)
Lec. Topic :- Asexual mode of reproduction
in plants.
Presentedby:-
Lt. Roshan Parihar, Asstt. Professor
Deptt.ofGenetics&PlantBreeding
Indira Gandhi Krishi Vishwavidyalaya
Raipur, C.G.
BTC College of Agriculture & Research Station ,Sarkanda,
Bilaspur,(CG)-495001

2. Asexual mode of reproduction
• Mode of reproduction determines the genetic constitution of crop
plants, that is, whether the plants are normally homozygous or
heterozygous.
• A knowledge of the mode of reproduction of crop plants is also
important for making artificial hybrids.
• Production of hybrids between diverse and desirable parents is
the basis for almost all the modern breeding programmes.
• The modes of reproduction in crop plants may be broadly
grouped into two categories, asexual and sexual.
Asexual reproduction does not involve fusion of male and female
gametes. New plants may develop from vegetative parts of the plant
(vegetative reproduction) or may arise from embryos that develop
without fertilization (apomixis).

3. Vegetative Reproduction
•In nature, a new plant
develops from a portion of
the plant body. This
may occur through
following modified forms.
1. Natural vegetative
• Underground stem
• Sub-aerial stems
• Bulbils
2. Artificial vegetative
• Stem cuttings

5. Natural vegetative mode
• Underground Stems
• The underground modifications of
stem generally serve as storage
organs and contain many buds.
These buds develop into shoots
and produce plants after rooting.
Eg.,
 Tuber : Potato
 Bulb : Onion, Garlic
 Rhizome : Ginger, turmeric
 Corm : Bunda, arwi.
• Sub-aerial Stems
• These modifications include
runner, stolon, sucker etc.,.
• Sub-aerial stems are used for the
propagation of mint, date plam
etc.
• Bulbils
• Bulbils are modified flowers that
develop into plants directly without
formation of seeds.
• These are vegetative bodies;
their development does not
involve fertilization and seed
formation.
• The lower flowers in the
inflorescence of garlic naturally
develop into bulbils.
• Scientists are trying to induce
bulbil development in plantation
crops by culturing young
inflorescence on tissue culture
media ; it has been successfully
done in the case of cardamom.

6. Artificial vegetative mode
• It is commonly used for the propagation of many crop species,
although it may not occur naturally in those species.
• Stem cuttings are commercially used for the propagation of
sugarcane, grapes, roses, etc.
• Layering, budding, grafting and gootee are in commonuse for the
propagation of fruit trees and ornamental shrubs.
• Techniques are available for vegetative multiplication through tissue
culture in case of many plant species, and attempts are being made
to develop the techniques for many others.
• In many of these species sexual reproduction occurs naturally but for
certain reasons vegetative reproduction is more desirable.

7. Significance of Vegetative Reproduction
• Vegetatively reproducing species offer
unique possibilities in breeding.
• A desirable plant may be used as a variety
directly regardless of whether it is
homozygous or heterozygous.
• Further, mutant buds, branches or seedlings, if
desirable, can be multiplied and directly used
as varieties.

8. Apomixis
• In apomixis, seeds are formed but the embryos develop without
fertilization. (without the fusion of male & female gametes).
• Consequently, the plants resulting from them are identicalin
genotype to the parent plant.
• In apomictic species, sexual reproduction is either suppressed or
absent.
• When sexual reproduction does occur, the apomixis is termed as
facultative. But when sexual reproduction is absent, it is referred to
as obligate.
• Many crop species show apomixis, but it is generally facultative.
• The details of apomictic reproduction vary so widely that a
confusing terminology has resulted.

9. • Parthenogenesis
• The embryo develops from embryo sac without
pollination. It is of two types
 Gonial parthenogenesis – embryos develop from
egg cell,
 Somatic parthenogenesis – embryos develop from
any cell of the embryo sac other than the egg cell.
• Apospory
• The embryo may develop from egg cell or some other
cell of this embryo sac.
• Apospory occurs in some species of Hieraceum,
Malus, Crepis, Ranunculus, etc.
o Diplospory
• Embryo sac is produced from the megaspore, which
may be haploid or, more generally, diploid.

10. • Apogamy
• In apogamy, synergids or antipodal cells develop
into an embryo.
• Like parthenogenesis, apogamy may be haploid or
diploid depending upon the haploid or diploid state
of the embryo sac.
• Diploid apogamy occurs in Antennaria, Alchemilla,
Allium and many other plant species.
• Adventive Embryony
• In this case, embryos develop directly from
vegerative cells of the ovule, such as nucellus,
integument, and chalaza.
• Development of embryo does not involve production
of embryo sac.
• Adventive embryony occurs in mango, citrus, etc.

13. Significance of Apomixis
• Apomixis is a nuisance when the breeder desires
to obtain sexual progeny, i.e., selfs or hybrids.
• It is of great help when the breeder desires to maintain
varieties.
• The breeder has to avoid apomictic progeny when he is
making crosses or producing inbred lines.
• But once a desirable genotype has been selected, it can
be multiplied and maintained through apomictic progeny.
• Asexually reproducing crop species are highly
heterozygous and show severe inbreeding
depression.
• Therefore, breeding methods in such species must avoid
inbreeding.

14. Thanks