M.Sc IV Sem (C.B.C.

S) Paper 3, Unit:2

Topic: Domestication, Plant Introduction and Acclimatization

Faculty: Dr. Deepa Srivastava, Assistant Professor, Department of Botany,

DDU Gorakhpur University, Gorakhpur

Domestication, Plant introduction and acclimatization

The present day cultivated plants have been derived from wild weedy species. The first step in
development of cultivated plant was Domestication i.e., bringing wild species under human
management which began over 11,000 years ago when human began agriculture.

Domestication of wild species is likely to continue for a long time in the future since human
needs are likely to change with time and the wild species of little importance today may assume
great significance tomorrow.

A notable case of recent and continuing domestication relates to several plant species for
production of biofuel. For example, jatropha (Jatropha curcas), a member of Euphorbiaceae
family cultivation is being popularized since oil extracted from its seeds is used to produce
biodiesel, which is supplemented (up to 5%) in diesel. This plant also has medicinal value, is
used as spice, and its supplemented (up to 5%) in diesel. This plant also has medicinal value is
used as spice, and its leaves enrich soil carbon. Kala jeera (Bunium persicum), a perennial spice,
was domesticated during 1990s in Himachal Pradesh and is being cultivated as an orchard crop.

Selection under Domestication

When different genotype present in a population reproduces at different rates, it is called

selection. A population may be defined as the group of individuals, which mate or can mate
freely with each other. Thus, a population consists of individuals of a single species growing in
the same locality. Selection is known as 1) Natural or 2) Artificial depending on the agency
responsible for it.

1. Natural Selection

Selection due to natural forces like climate, soil, biological factors e.g., diseases, insects, pests
etc., and other factors of the environment is called Natural selection. It occurs in natural
population i.e., wild form and wild species and determines the course of their evolution.

In 1962, Nicholson proposed that natural selection may be seen to operate through two
mechanisms.
 A. Environmental Selection Environmental selection acts against all such genotypes
that are unable to cope with the environmental stresses. As a result, the population
consists ultimately of only those genotypes that can survive the prevalent
environmental stress and are able to reproduce.
B. Competition: Natural selection through competition occurs in crop population where
a plant takes up more water, nutrients or light than another, and at expense of the
other. Therefore, the more successful is a plant in exploiting resources, the greater
will be its potential to be represented in the succeeding generations and it will be
selected through competition.

2. Artificial Selection
Artificial selection is carried out by human and is confined to domesticated species. It
allows only the selected plant to reproduce, ordinarily makes plants more useful to
humans and generally leads to a marked decline in genetic variability in the selected
progenies/populations.

Type of Selection
Selection is grouped into following three types.
1. Directional Selection
2. Stabilizing selection and
3. Disruptive selection

In plant breeding situations, selection is almost always directional aiming to achieve the maximal
expression of targeted characters.

Directional Selection:

When individual having 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 act against the extreme phenotype, it is
termed as stabilizing selection.

Disruptive Selection:

This type of selection succeeds directional selection in such natural population that are subjected
to distinct ecological niches that may be spatial, temporal (seasonal or long-term cycles) or
functional (e.g., male and female of species) in nature. In each ecological niche a different
“phenotypic optima is selected for so that the population ultimately consists of two or more
recognizable form, such selection is called disruptive selection. The consequences of such a
selection depend mainly on the following two factors.
 i. Whether the different optimal phenotypes are independent of or dependent on each
other for their maintenance.
ii. The rate of gene flow between them.

Disruptive selection maintains polymorphism in population. Since disruptive selection is

directional in nature within each ecological niche of the habitat, it favours dominance and
epistasis. In addition, it often leads to the establishment of integrated “supergenes” e.g., in case
of male and female forms of a species. A “supergene” is a set of closely linked genes that
together lead to the development of a specific optimal phenotype. e.g., male, and female form.
Domestication of crops is believed to have occurred independently in the following at least six
regions.

i. Mesoamerica
ii. The South Andes
iii. The Near East
iv. Africa (probably the Shel and the Ethiopian highlands)
v. South East Asia
vi. China

Almost all the characteristics of plant species have changed under domestication due to
accumulation of spontaneous mutations. Some of the important changes that have occurred under
domestication are listed below.

1. Elimination of or reduction in shattering of pods, spike tec has taken place in most of
the cultivated species.
2. Elimination of dormancy has taken place in several crop species. Eg Barley, Wheat,
mungbean
3. Decrease in toxins, the bitter principle of cucurbitaceous plant provides an example of
this.
4. Plant type has been extremely modified. The cultivated plants show altered tillering,
branching leaf characters etc.
5. Decrease in height e.g., cereals, millets etc
6. Increase in height e.g., Jute (Corchorus sp.) Sugarcane (S. officinarum), forage grasses
etc.
7. Life cycle become shorter e.g., cotton (Gossypium sp.), pigeon pea (Cajanus cajan) etc.
8. Increase in size of their grains or fruits in most of the crops.
9. Increase in economic yield noticeable as well as desirable changes under domestication
in every crop species.
10. Asexual reproduction has been promoted e.g., Sugarcane, potato (Solanum
tuberosum), sweet potato (Ipomoea batatas)
11. Preference for polyploidy: many of the domesticated plant species are polyploids e.g.,
potato, wheat, sweat potato, tobacco (Nicotiana sp.) etc.
 12. Shift in the sex form, self-incompatibility has also been eliminated in several crop
species.
13. Variability within a variety has drastically decreased, the extreme case is represented
by pure line varieties which are completely homozygous and consist of a single genotype.

Plant Introduction
Plant Introduction consists of taking a genotype or a group of genotypes of plants into a new
environment where they are not grown before. Thus, plant production may involve new varieties
of a crop already grown in an area, wild relatives of the crop species or a totally new crop species
for the area. Often the material is introduced from the other countries or continents but the
movement of crop varieties from one environment to another environment within the same
country is also the introduction.

Plant introduction may be of two types.

1. Primary Introduction
2. Secondary Introduction

Primary Introduction

When the introduced crop or variety is well suited to a new environment it is directly grown or
cultivated without any alternation in the original genotype. This is known as Primary
introduction, example IR8, IR28, IR36 rice variety, semidwarf wheat varieties Sonara 64,
Lerma Rojo, oil palm varieties introduced from Malaysia, Mashuri rice from Malaysia.

Secondary Introduction

The introduced variety may be subjected to selection to isolate a superior variety or it may be
used in hybridization programme to transfer some useful traits this is known as Secondary
Introduction.

In Soyabean EC39821 introduced from Tiwari is subjected to selection and variety Co-1 was
developed.

Objective of Plant Introduction

• To introduce new Plant species there by creating ways so better new varieties are
produced.
• To introduce high yielding variety to increase food production e.g., Rice and Wheat
• To enrich the germplasm collection e.g., Sorghum, groundnut.
 • To get new source of resistance against biotic and abiotic stresses.

Plant Introduction Agencies in India

A centralized plant introduction agency was initiated in 1946 at IARI, New Delhi as Plant
introduction scheme in the Division of Botany and was funded by ICAR, New Delhi. National
Bureau of Plant Genetic Resources (NBPGR) was established in 1976. The bureau is
responsible for the introduction and maintenance of germplasms of agriculture and horticulture
plans. The Botanical Survey of India was established in 1890, it was responsible for the
introduction, testing and maintenance of plant materials of botanical and medicinal plants. But
the activities of all the agencies involved in plant introduction are coordinated by NBPGR, New
Delhi. All the introduction in India must be routed through NBPGR, New Delhi.

Procedure for Plant Introduction. Plant introduction involves following steps:

i. Procurement
ii. Quarantine
iii. Cataloguing
iv. Evaluation
v. Multiplication
vi. Distribution

1. Procurement:

Procurement is obtaining plant material; it may be by any of these methods.

1. Gifting
2. Exchange
3. Purchasing
4. Exploration

But all the introductions must be routed through NBPGR, New Delhi

2. Quarantine: Quarantine means to keep material in isolation to prevent the spread of

disease etc, present in them to other materials. Plant material introduced must be free
from any contamination, materials that are suspected to be contaminated are fumigated or
are given other treatments to free them from contamination.
According to Destructive Insect and Pest Act, 1914(DIP, 2014), All plant produce
imported in India must be free from disease, insect pest and weeds.

The quarantine of such plant produce is done by following three agencies depending on the plant
species.
 1. NBPGR, New Delhi: All propagules of Agriculture and horticulture species including
transgenic material.
2. FRI, Dehradun: Propagules of Forest trees
3. IBS, Kolkata: Propagules of remaining plant species.

3. Cataloging:
Each germplasm accession is given an accession number. In India, this number is
prefixed with either

EC: Exotic collection,

IC: Indigenous collection
IW: Indigenous wild collection
4. Evaluation: Assessment of Potential and performance of new introduced variety is done
in different regional stations of NBPGR.
NBPGR: 8 REGIONAL Station substations
1. Regional Station, Akola (Maharashtra)
2. Regional Station, Bhowali (Uttar Pradesh)
3. Regional Station, Hyderabad (Andra Pradesh)
4. Regional Station, Jodhpur (Rajasthan)
5. Regional Station, Shillong (Meghalaya)
6. Regional Station, Shimla (Himachal Pradesh)
7. Regional Station, Thrissur (Kerala)
8. Regional Station, Srinagar (J &K)
Exploration Based centre of NBPGR.
1. Exploration Base Centre, Cuttack (Orissa)
2. Exploration Base Centre, Rachi (Jharkhand)
5. Multiplication: The plant variety are propagated, and necessary field trial are done.
6. Distribution: If suitable the new variety is released.

Purpose of Plant Introduction

Plant introduction is the oldest and highly effective approach to create genetic variation. The
chief objective of plant Introduction are:

1. Entirely New Crops: Many of our important crops e.g., Maize, Potato, Tomato, Tobacco
etc. are introduced.
2. New Varieties: The Mexican semi dwarf wheat varieties Sonora 64 and Lerma Rojo,
semidwarf rice varieties TN1 and IR8 etc. are more recent examples of this type.
3. Utilization in Crop Improvement Programmes: Often the introduced material are used
for hybridization with local varieties to develop improved varieties. Pusa Ruby tomato
was derived from cross between Meeruty and Sioux, an Introduction from USA.
 4. Saving a Crop from a disease or Pest: Coffee was introduced in South America from
Africa to prevent losses from leaf rust. Hevea rubber was brought to Malaya from South
America to protect it from leaf disease.
5. Utilization in Scientific studies: N.I. Vavilov developed the concept of centres of origin
and that of homologous series in variation from the study of a vast collection of plant
types
6. Used for Aesthetic value: Ornamentals, shrubs and lawn grasses are introduced to
satisfy the finer sensibilities of humans.

Important Achievements

1. New Crop Species: The crops introduced in India such important ones as potato, maize,
groundnut, chillies, coffee, Hevea, rubber, guava, pineapple, papaya etc.
2. Direct Release as Varieties: Semidwarf wheat varieties Sonora 64 and Lerma Rojo were
released directly for cultivation. TN1 rice introduced from Taiwan and IR 8, IR21 and IR
36 etc. from IRRI, Philippines were directly released as varieties.
3. Varieties Selected from Introductions: Two varieties of wheat, Kalyan Sona and
Sonalika were selected from material introduced from CIMMYT, Mexico; they
dominated wheat cultivation in India for about one decade. Other varieties developed
through selection are Jamnagar Giant and Improved Ghana pearl millet, Pusa Lal and
Pusa Sunehari sweet potato, Pusa Basmati etc.
4. Varieties Developed through Hybridization: The hybrid maize, jowar, bajra and rice
varieties generally have one parent, the male sterile female parent which is either an
introduction or derived from introduction. All the sugarcane varieties have been derived
from the introduced noble canes (S. officinarum)

Merits of plant Introduction

1. Introduction provides entirely new crop plants.

2. It provides superior varieties either directly after selection or through hybridization.
3. Introduction and exploration are the only feasible means of germplasm collection.
4. It is very quick and economical method of crop improvement, particularly when the
introductions are released as varieties either directly or after selection.
5. Crops may be introduced in new disease-free areas to protect them from damage e.g.,
coffee and rubber.

Demarits of Plant Introduction

1. Weeds: Argemone Mexicana, Eichhornia crassipes and Phylaris minor are some
noxious weeds that entered India along with plant Introduction
2. Diseases: Late blight of potato was introduced from Europe in 1883, Flag smut of wheat
was introduced from Australia, coffee rust came from Ceylon in 1876 and bunchy top of
banana arrived from Ceylon in 1940.
 3. Insect Pests: Potato tuber moth came from Italy in 1900.
4. Ornamentals turned Weeds: Water hyacinth and Lantana camara were both
introduced in India as ornamental plants, but now noxious weeds.
5. Threat to ecological balance: Eucalyptus spp. Introduced from Australia cause a rapid
depletion of subsoil water reserves.

Acclimatization
Acclimatization is the process that leads to the adaptation of a variety, line or population to
a new environment. Acclimatization is brought about by a faster multiplication of those
genotype (present in original population) that are better adopted to the new environment. Thus,
acclimatization is the result of natural selection.

The extent of acclimatization is determined by

1. Mode of Pollination
2. Magnitude of genetic variability present in original population
3. Duration of life cycle of crop
4. Mutation

Genetic variability is the prerequisite for acclimatization, therefore, the greater the genetic
variability present in the original population the more is the extent of acclimatization. The
magnitude of Acclimatization is directly proportional to Genetic variability.

A ∞ Genetic variability

Life cycle duration is important because annual crop would produce several generations by the
time a perennial crop produces one generation. Each generation would produce new gene
combinations, thereby facilitating acclimatization. The magnitude of Acclimatization is inversely
proportional to life period that is the annual plants will be more easily acclimatize then perennial
plants.

A ∞1/Life Period

Cross pollination leads to the greater gene recombination then self-pollination. As a result,
cross pollination is more helpful in acclimatization.

Acclimatization is directly proportional to cross pollination.

A ∞ Cross pollination

Acclimatization is inversely proportional to self-pollination.

 A∞1/Self pollination

Mutation play an important role in acclimatization but if become important only where the
period of acclimatization is very long.

REFERENCES:

1. Plant Breeding Principles and Methods by B.D.Singh, Kalyani Publishers

ASSIGNMENTS:

Write notes on the following:

1. Centre of Diversity
2. Plant introduction
3. Plant acclimitization
4. NBPGR
5. Domestication
6. N.I. Vavilov