This is a part of Core Course VI : Economic Botany: Crop domestication and loss of genetic diversity; crop introduction

1. Economic Botany
Core Course VI
Unit1:Lecture2: Origin of cultivated
plants
Crop domestication and loss of genetic Diversity;
Examples of major plant introductions;
Importance of Germplasm diversity
Ref :A Text Book of Botany Volume IV; Bhattacharya, Ghosh & Hait
Plant Breeding, P.Satya
Dr Rita Som Paul
Associate Professor
Botany Department Siliguri College

2. Crop domestication and loss of
genetic Diversity
• Domestication is selection for desirable
characters like higher yield,non-shattering
type of grain and elimination of undesirable
characters of wild species through several
generations
• Mere cultivation of crop does not qualify for
domestication
• Thus, domestication is a form of plant
breeding

4. • Domestication of plants is as old as domestication
of animals about 14,000 years BP(Before present).
Rice was the earliest domesticated crop.
Sl No Crop Evidence of
domestication
(years BP)
Place
1 Rice 15,000-13,000 Korea, Indo-
China
2 Eikorn wheat 10,000 Near East
3 Maize 6300 Central Mexico
4 Bottle gourd 12,000 Asia and Africa
5 Squash 10,000 Central Mexico
6 Pearl Millet 3000 Central Africa
7
8
Barley
Fig
10,000
10,000
Near East
Near East

5. Pollination cross-pollinated self-pollinated

6. Consequences of domestication
• Loss of genetic diversity- loss of divergent alleles
in a species-genetic erosion
• Genetic pollution-invasive species, transgenes
• Dependence of the species on human
interference/help for survival- loss of fitness-
non-competitive
• Loss of species diversity – out of 13 million plant
species, only 7000 plant species are cultivated
and only 30 supply most of human needs for
food.

7. Loss of genetic diversity
• Two types of genes
• 1. directly controlling the traits selected by the
humans (seed size, seed number, fruit colour)
directly influenced by selection – variability at
these loci is drastically reduced
• 2. do not directly control the traits under
selection - variability reduced to a lower extent
(Eg.embryo size)
• -- Bottleneck effect; narrowing of genetic base

9. Examples of major Plant
Introductions
• Introduction - Transfer of genotype of crop
plants either singly or in groups from one place
of cultivation to a totally different new area for
the purpose of cultivation . The main target is to
• Method:Import of germplasm
• Indian Agencies :
• NBPGR (National Bureau of Plant Genetic
Resources)
• BSI (Botanical Survey of India)
• FRI(Forest Research Institute)

10. Plant Introduction
• Primary Introduction: the variety os well-
adapted and can be cultivated without any
genotype changes Eg Rice -IR8
(fromPhillipines) and IR36; wheat – Lerma
Roja and Sonara 64 (from Mexico)
• Secondary Introduction –variety introduced is
initially subject to selection and /or
hybridization Eg Sonalika and Kalyan Sona of
wheat are selected from Mexican varieties

11. Examples of primary introductions
Sl No Crop Variety
1
2
Wheat
Rice
Lerma Rojo-64;Sonora-64(Mexico)
IR8;IR50(Phillipines)
3
4
Sunflower
Groundnut
Peredovik(USSR)
M13(USA)
5
6
Soybean
Pea
Lee(USA)
Harbhajan(Portugal)
7
8
Tomato
FrenchBean
Labonita(USA);FireBall(Canada)
Kentucky Wonder(USA)
9
10
Water Melon
Apple
SugarBaby(USA)
Delicious-II(USA)

12. Examples of secondary introductions
Sl No Crop Variety
1 Cowpea Rituraj
2 Cauliflower Pusa SnowBall-1
3 Tomato Pusa Ruby
4 Water
Melon
Akra Manik

13. Importance of Germplasm Diversity
• Germplasm - total genetic resource of an
organism (usually of a species)
OR
- a collection of living tissues (usually a species)
from which new plant can be grown (seed,
piece of stem or the whole plant etc)- it
contains the information for the total species
genetic makeup

14. Importance of Germplasm Diversity
• PGR (Plant Genetic Resources)/Plant
Biodiversity
• Usable (direct use) value – germplasm of crop
plants especially is important for survival of
humans. 1.Some gene may be present in wild
relative that might be useful at some stage for
the plant breeder
• 2.Plants used for clothes, furniture, medicine
• Non-use (indirect use) value – support to
evolution; balancing of ecosystem ; aesthetic
value; CO2/O2 balance;

15. Importance of Germplasm Diversity
• 1. Population (a group of individuals of same
species) with large gene pool has a better
chance of survival
• 2.To improve the existing plants and form
new varieties
• 3. Reduction of incidents of unfavourable
traits being inherited (inbreeding depression
reduction)

16. Gene banks- means to preserve
germplasm (mainly crop plants)
Sl No Gene bank Country No of accessions
held
1 National Seed storage
Laboratory
USA 268,000
2 Institute of Crop Germplasm China 300,000
3 Vavilov Institute of Plant
Industry
Russia 177,680
4 National Bureau of Plant
Genetic Resources
India 343,000
5 National Institute of
Agrobiological Research
Japan 146,000