Presentation on sexual reproduction, classification and significance in plant breeding

1. SEXUAL REPRODUCTION-
CLASSIFICATION AND SIGNIFICANCE IN
PLANT BREEDING
Submitted to: Dr. Kaushik Kumar Panigrahi
Submitted by: Priyanka Naik
05HO/16

2. Reproduction in animals occurs in two primary ways, through sexual reproduction
and through asexual reproduction.
In sexual reproduction, two individuals produce offspring that have genetic
characteristics from both parents. So sexual reproduction is defined as the production of
offspring by the fertilisation of a male and a female gamete. It must involve fusion of the
gametes.
In plants also separate gametes are produced in specialized structure called the flower.
Then these gametes come together to get fused. Generally the male gamete is transferred
to the female gamete, thus involving a process called pollination which scientifically is
defined as the transfer of male gamete from the anther to the stigma. And according to this
the sexually reproducing species are classified into, self pollinated, cross pollinated and
often cross pollinated species.

3. SELF- POLLINATED SPECIES
• Self- pollination is otherwise known as autogamy.
The prefix "auto" means "self".
• An individual that can undergo autogamy can
fertilize itself. Known as hermaphrodites, these
individuals have fully functioning male and female
reproductive system parts necessary to make both
the male and female gamete for that individual.
They do not need a partner to reproduce, but some
may still be able to reproduce with a partner if the
opportunity arises

4. • Rice, Wheat, Barley, Oats, Chickpea, Pea, Cowpea, Lentil, Green gram, Black gram, Soybean,
Common bean, Moth bean, Linseed, Sesame, Sunhemp, Chillies, Brinjal, Tomato, Okra, Peanut,
etc. are some examples of self pollinating species.
• In case of autogamy the male and female gametes are produced on the same plant. And the
pollen is transferred from the anther to the stigma of the same flower or a different flower on
the same plant which is obviously genetically similar. The 2nd method of autogamy is
particularly known as geitonogamy.
• Self pollination causes increase in homozygosity and
decrease in heterozygosity. But the cross pollinated species
show inbreeding depression on self pollinating which is not
shown by self pollinating species.
• These inbreeders have narrow adaptability generally and
are less flexible.

5. CROSS POLLINATED SPECIES
• Cross pollination involves the transfer of pollen
grains from the flower of one plant to the stigma
of the flower of another plant. It is also called
xenogamy or allogamy.
(Gk. Xenos = strange, gamos = marriage) or
allogamy (gk, allos = other, gamos = marriage).
• These are also called as out breeders which
show inbreeding depression when self pollinated.
• As the pollens are transferred to a genetically
dissimilar plant so ore variability is seen in the
individuals having more adaptability ad flexibility.

6. • New gene combinations are allowed in allogamy, increasing heterozygosity and the variability
is distributed over the entire population.
• Corn, pearl millet, rye, alfalfa, radish, cabbage, sunflower, sugar beet, castor, red clover, white
clover, safflower, spinach, onion, garlic, turnip, squash, muskmelon, watermelon, cucumber,
pumpkin, oil palm, carrot, coconut, papaya, etc. are some examples of cross pollinating species.
• A agent is must in case of allogamy to effect pollination. Pollination is effected by many
agents like wind, water, insects etc. On the basis of the agents that bring pollination, the mode of
pollination is as follows :
a. Anemophily (Wind) b. Hydrophily (Water) c. Entomophily (Insects) d. Ornithophily (Birds)
e. Chiropterophily (Bats) f. Myrmecophily (Ants) g. Malocophily (slugs and snails) h. Ophiophily
(snakes) i. Cantharophily (Beetles)
• There is a considerable loss in the pollen number as most of them do not get germinated on
the stigma.

7. OFTEN CROSS POLLINATED SPECIES
• In many self pollinating species, cross pollination may occur up to 5% or even reach to
30%, such species are referred as often cross pollinating species.
• Jowar, cotton, broad bean, jute, rai , Brassica campestris var.Yellow sarson (yellow
sarson) B. campestris var. Toria, Cotton, sorghum, tobacco, safflower etc. are some
examples of cross pollinated species.
• Genetic architecture of such crops is intermediate between self and cross pollinated
species.
• These generally reproduce by self pollination but cross pollination is also seen to a certain
extent.

8. Significance of Sexual Reproduction in Plant Breeding
• Self pollinated species do not show inbreeding depression, but may exhibit considerable
amount of heterosis. Therefore the aim of breeding methods is generally to develop
homozygous variety.
• Likewise, cross pollinated species are highly heterozygous and show mild inbreeding
depression and considerable amount heterosis. Breeding methods in such species aims at
improving the crop species without reducing heterozygosity to an appreciable degree.
Usually hybrids or synthetic varieties are the aim of the breeder where the seed
production of such varieties is economically feasible.
• The breeding work is done keeping an eye on the nature of the plant and its breeding
method.

9. • In case of accepted and developed hybrids or selections, we need to maintain there
genetic characteristics as much as we can so that their genetic architecture will not be
altered in the subsequent generations.
• Self pollination is very important in case we want to operate with back cross method of
plant breeding, in which after crossing the F1 with the parent self cross is done for few
subsequent generations so as to fix the characteristics in the progeny.
• In case of breeding methods like secondary plant introduction the, the plant after
introduction may be subjected to some crosses so as to make it adjusted to the introduced
place.
• To incorporate a desired characteristic or trait into a plant from another cross pollination
is done.

10. • When we want to recover a plant from inbreeding depression we apply cross pollination
so as to increase heterozygosity.
• We even can develop hybrids with cross pollination according to our terms and
conditions.
• In case we want to incorporate any desired traits from a plant to another like disease or
insect-pest resistance so as to make a more improved plant to get a higher yield we can
achieve by sexual reproduction.
• When we adopt a method like bulk crossing for developing a new superior variety we
generally grow seeds by bulking and then to select seeds from the next generation we
have to self them; here comes the role of self pollination.

11. • But there are some plants which are dioecious and they can never be self pollinated, so
to maintain their genetic architecture of the desired and already developed varieties, they
are subjected to controlled pollination. In this case one parent is crossed with another in a
controlled manner by taking the pollen and pollinating on the previously bagged flower of
the desired and selected female plant so that not much traits of the variety will get
affected. This is generally done in strictly dioecious plants; for example, papaya.
• Generally, self pollination is used more in the breeding work as this do not allow much
variation because there is no recombination of the genes, involved here. So this is
adopted most of the times.

12. THANK YOU