Dr. NAVEENKUMAR K.L Assistant Professor Dept. Of Genetics and Plant Breeding

1. Dr. NAVEENKUMAR K.L
Assistant Professor
Dept. Of Genetics and Plant Breeding
UAHS Shivamogga
DOMESTICATION

2. What is domestication..?
 Domestication is the process of bringing wild species under
human management.
 Plant domestication is the genetic modification of a wild species
to create a new form of a plant altered to meet human needs
(Doebley et al., 2006)
 Present day cultivated plants have been derived from wild
weedy species.
 The process by which humans actively interfere with and
direct crop evolution.
 Individuals that exhibit desirable traits are selected to be bred,
and these desirable traits are then passed along to future
generations

7. How much domestication
 About 5000 species have been grown for human food – less than 1% of
all plant species thought to exist
 Today about 150 species are commercially grown for food (not including
spices)
 About 50 very productive species supply almost all of our caloric needs.
Benefits of Domestication-
 10,000 years ago, before agriculture began, the world’s total human
population was about 5 million.
 There was one person for every 25 square kilometers. Today we have
more than 7 billion people, with a density of just over 25 people per
square kilometer.
As agriculture developed humans selected for:
1. Plants that provide enough calories to meet our basic energy needs.
2. We also selected for a balanced nutritional intake - this tends to
develop in any system where the cultivator eats and depends upon on
what he/she grows.

8. Types of Domestication
1. Incidental
Didn’t happen on purpose. Hunter/gatherers dropped
seeds, scared off natural herbivores, disrupted natural
environments so that plants could grow.
2. Directed
Humans and plants became dependent on each other, so
better plants helped people get healthier, planting more
(and maybe improved) plants, etc.
3. Agriculture
Human intervention in crop Husbandry, Cultivation and
Selection.

9. Selection under Domestication
Selection: When different genotypes present in a
population reproduce at different rates, it is called
selection.
 A population may be simply defined as the group of
individuals, which mate or can mate freely with each
other.
Selection is grouped into two types, on the basis of the
agency responsible for it
1. Natural selection
2. Artificial selection

10. Natural Selection
The selection that occurs due to natural forces like climate,
soil, biological factors (e.g., diseases, insect pests, etc.) and
other factors of the environment is called natural selection.
In 1962, Nichlson proposed that natural selection may be seen
to operate through two mechanisms, viz.;
(l) Environmental selection
(2) Competition.
Environmental selection acts against all such genotypes that
are unable to cope with the environmental stresses.
It is through competition occurs in crop populations where a
plant takes up more water, nutrients or light than another at
the expense of the other.

11. Artificial Selection
 It is carried out by man and is confined to domesticated
species.
 It allows only the selected plants to reproduce, ordinarily
makes plants more useful to man and generally leads to a
marked decline in genetic variability in the selected
progenies/populations.
Types of Selection-
1) Directional selection,
2) Stabilizing selection
3) Disruptive selection.

12. Directional Selection: When individuals having the extreme
phenotype for a trait or a group of traits are selected for, it is
called directional selection.
Stabilizing Selection: When selection favours the intermediate
phenotype and acts against the extreme phenotypes, it is
termed as stabilizing selection.
Disruptive Selection: In each 'ecological niche' a different
'phenotypic optima' is selected for so that the population
ultimately consists of two or more recognizable forms; such a
selection is called disruptive selection.

13. Changes in plant species under domestication
1. Elimination of or reduction in shattering of pods spikes etc in
cultivated species (Pulses)
2. Elimination of dormancy (Barely, wheat, Mung)
3. Decrease in toxins (cucurbitaceous plants)
4. Decreased plant height (cereals, millets)
5. Increased plant height (sugarcane, jute, fodder grasses)
6. Life cycle has become shorter (cotton, arhar)
7. Increased economic yield
8. Variability within the a variety has drastically decreased under
domestication.

14. Domestication syndrome
The domestication syndrome can be defined as the
characteristic collection of phenotypic traits associated
with the genetic change to a domesticated form of an
organism from a wild progenitor form.

15. Effect of selection during domestication
A selective sweep is the reduction or elimination of variation among the nucleotides in
neighboring DNA of a mutation as the result of recent and strong positive natural selection