Journey From Wild to Domestication; Genetic Enhancement- Need for Genetic Enhancement; Genetic Enhancement in

Pre Mendelian Era and 21st Century; Genetic Enhancement and Plant Breeding;

Reasons For Failure in Genetic Enhancement; Sources of Genes/ Traits-

Novel Genes For Quality.

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K.K. Chandel

Ph. D. ScholarGenetics and Plant

Breeding

History of Agriculture

Hunter-Gatherers

Neolithic Revolution◦Domestication of Plants and Animals◦Diffusion of Agriculture

Agricultural Industrialization

The “Green Revolution”◦Hybrids, scientific application of fertilizer,

pesticide, and water

Modern Agribusiness

Plant Domestication

More than just planting seeds or transplanting

Most plants inedible or otherwise unusable

Most plants unsuited for primitive domestication

Not every locality has abundant plants suitable for human use

Need nutritional balance

Requires changes in plant characteristics

Five Levels of Domestication

1. Unconscious selection of plants for desirable traits (9000 BC)

2. Conscious cultivation of plants with desired traits (BC)

3. Deliberate breeding to improve traits (1700)

4. Scientific breeding: genetic mechanism known and exploited (1900)

5. Direct genetic manipulation (2000)

Domestication- It’s the process of bringing wild species under human

management.

Which began ~ 10,000 years ago when man began agriculture First domesticated plants were cereals, legumes and other field crop species (fruits and roots)

Plant domestication-Domesticated plants differ from their wild progenitors in

several morphophysiological traits, most of which are associated with seed retention and germination, growth habit, size, coloration, and/or edibility of economically important organs

Domestication syndrome (DS)- Denotes differences between domesticated plants and their wild

progenitors.

Selection under Domestication -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 (2)artificial

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.

Natural selection- 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.

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.

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.

Most domesticated food plants have been selected for:

Large plant parts

Soft edible tissue

Thick flesh with intense color

Fruits attached to tough stems

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. This usually comes from cereal grain or root carbohydrates.

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.

GENETIC ENHANCEMENTGenetic enhancement is now necessary and useful but it is not

yet well recognized as being so. This is evident because there is no group of scientists or professionals who call themselves "genetic enhancers", or "pre-breeders"

Genetic enhancement, up to now, has utilized standard hybridization, segregation, and whole plant selection techniques. Backcrossing, cyclic population improvement, and pedigree selection among selfed progeny are examples of methods employed. But with the advent of molecular genetics and cell biology, a new kind of biotechnology assisted genetic enhancement (or prebreeding) is possible. Heretofore unavailable genes for insect resistance may be transferred from alien species into elite genotypes

IntroductionThe term "enhancement" was first used by Jones (1983)

which according to him can be defined as transferring useful genes from exotic or wild types into agronomically acceptable background.

Rick (1984) used the term pre-breeding or developmental breeding to describe the same activity. Thus "genetic enhancement" or "pre-breeding" refers to the transfer or introgression of genes or gene combinations from unadapted sources into breeding materials (FAO, 1996)

However, enhancement has been more popularly adopted by PGR scientists. It is an emerging concept emphasizing the use of plant genetic resources.

Need for Genetic EnhancementTo meet the market requirement, plant breeders have to

develop improved cultivars, which is possible through use of elite breeding material which is developed through pre- breeding. In the past, more attention has been given to adaptation and performance through selection than to generation of new variability to fulfill immediate needs.

In the past, crop improvement has led to narrowing down of genetic base resulting in slower progress (genetic gain) in plant breeding and increased risk of genetic vulnerability.

This has resulted in the accumulation of unused potential germplasm. In order to break these bottlenecks and to create superior gene pools, genetic enhancement or pre-breeding is required to enhance the value of germplasm.

Need for Genetic Enhancement

1. In improving the level of resistance to biotic and abiotic stress.

2. In improving quality characters such as fibre length, strength, fineness, maturity and uniformity.

3. In developing early maturing genotypes, which can fit well in multiple cropping systems.

4. In developing plant types suitable to machine picking etc.5. Use of germplasm will help in broadening the genetic

base of cultivars as well as in creating vast genetic variability.

6. It will also help in value addition of different genotypes through genetic enhancement.

Methods of Genetic EnhancementIntrogression :Introgression is transfer of one or more genes from

exotic/un-adapted / wild stock to adapted breeding populations. This is achieved by making crosses between the donor and the recurrent parent. The concept of introgression through backcross was evolved by Dr. Edgar Anderson

Backcross method :The parent from which desirable genes are to be

incorporated is used as donor parent and the parent which is to be further improved is used as the recurrent parent. Six generations of conventional recurrent backcrossing are required to transform a genetic stock.

Methods of Genetic Enhancement(i) Recurrent backcross: This method involves

successive backcrossing of the cross made between donor and the recurrent parent with the recurrent parent with or without selection. With this method, the monogenic or oligogenic traits with high heritability can be easily transferred.

(ii) Inbred backcross: This method involves a limited number of backcrosses (usually one or three). This is followed by several generations of selfing. This method was first given by Wehrhahn and Allard, 1965. This method results in the development of a population of more than 50% of lines that are homozygous and have a common genetic background similar to the recurrent parent.

Methods of Genetic Enhancement

(iii) Congruity backcross: This method was originally proposed by Haghighi and Ascher, in 1988.

In this method, backcrossing is done to both donor and recurrent parent in alternate generations. This method was used successfully to recover progeny with increased fertility from Phaseolus vulgaris and P. acutifolius crosses. It was possible to obtain progenies with intermediate morphologies rather than morphologies resembling one or the other parent. This led to effective recombination through the increased levels of heterozygosity.

Methods of Genetic Enhancement

Marker Assisted Backcross Method (MAS)This method is used to transfer specific elite allele

at a target locus from a donor line to a recipient line. The number of target genes involved in the selection and the expected level of line conversion must be defined.

Uses of Biotechnology in Genetic EnhancementThere are two main approaches in biotechnology

which are used in pre-breeding viz., (i) genetic transformation and (ii) cell culture techniques.

Problems associated with Genetic Enhancement

1. Cross incompatibility in inter-specific crosses.2. Stability barriers and chromosome pairing in hybrids have restricted the access to genes from wild species into cultivated ones.3. Linkage drag.4. Hybrid inviability and sterility.5. Small sample size of inter-specific hybrid population.6. Restricted genetic recombination in the hybrid population.7. Lack of availability of donors for specific traits viz. resistance to diseases, pests and bollworm.8. Exchange and accessibility of cultivated species germplasm material has become difficult due to legal restrictions like IPR.

The Manipulation of Genes for quality

Gene– a segment of DNA in a chromosome specifying a particular protein or polypeptide chain, a tRNA or an rRNA

Recombinant DNA – any artificially created DNA molecule which brings together DNA sequences that are not usually found together in nature.

Gene Manipulation – a variety of sophisticated techniques for the creation of recombinant DNA, which are then introduced into living cells.

Genetic Engineering – the isolation, manipulation, recombination, and expression of DNA often for the development of genetically modified organisms.

Finding the Right Gene

All genetic engineering starts by identifying and isolating the correct clone containing the gene.

This can be done by: Making gene libraries from total genomic DNA Or, if the gene is identified, cloning the DNA fragment by PCR (polymerase chain reaction)

cDNA Libraries‐These libraries will have only contain DNA from transcribed genes of spp.

Genomic DNA Libraries ‐These libraries will have contain all DNA sequences (Intron+Exons).

Constriction of gene library

Polymerase Chain Reaction (PCR)

Novel gene Transfer

Using the New Gene

The main reason for creating a new gene is to produce the protein. Some proteins are used to make plants that are resistant to insects or insecticides

Some proteins are used to enhance the characteristics of the product

Some proteins are used to make pharmaceuticals

Flavr Savr Tomato

Insulin

Genetically Modified Plants Using Gene-

• Herbicide resistant

• Pesticide resistant

• Insect resistant

• Drought tolerant

• Extreme temperature tolerant

• Have added nutrients, such as vitamins and minerals

Roundup ready crops- Roundup is a common herbicide manufactured by

Monsanto that is harmful to weeds and plants alike For this reason, Monsanto developed a line of “Roundup ready” crops that are resistant to the herbicide By inserting gene 5’‐enolpyruvylshikimate‐3’‐phosphate (EPSP) from the bacteria Agrobacterium, plants such as corn, soybeans, cotton, and alfalfa could be made herbicide resistant

Insect resistanceCorn, cotton, and several other plants have been

genetically modified to be insect resistant.

Insect resistance in crops is accomplished by identifying and isolating a gene from the soil bacterium Bacillus thuringiensisthat produces a toxin called Crythat is toxic to plant insects.

By cutting and inserting the gene of interest from B. thuringiensisinto plant DNA, a new genetically modified plant is created that is resistant to insects.

Benefits of insect resistance

GM cotton plants that are insect resistant are protected from tobacco budworm, bollworm, and pink bollworm caterpillars.

GM corn plants that are insect resistant are protected from European corn borers and corn rootworms.

These insects cause severe damage to the plants and ultimately prove costly to the farmer. GM plants are beneficial in that they increase crop yield and save farmers time and money by having to use less insecticides.

Rice, a staple food in many countries, has been genetically modified to be an improved source of vitamin- A

This GM rice is able to biosynthesize β‐carotene, which leads to production of vitamin A in the human body.

GM plants with added nutrients ‐Rice

The Golden Rice Fact

Rice, the principal crop of India is extremely low in vitamin A.

This deficiency can lead to blindness, diarhae, malaria and tuberculosis.

It was contributed by two German research team headed by Potrykus and Peter Beyer, 1999.

-Carotene Pathway Problem in Plants

IPP

Geranylgeranyl diphosphate

Phytoene

Lycopene

-carotene(vitamin A precursor)

Phytoene synthase

Phytoene desaturase

Lycopene-beta-cyclase

ξ-carotene desaturase

Problem:Rice lacks

these enzymes

NormalVitamin A

“Deficient”Rice

The Golden Rice Solution-Carotene Pathway Genes Added

IPP

Geranylgeranyl diphosphate

Phytoene

Lycopene

-carotene(vitamin A precursor)

Phytoene synthase

Phytoene desaturase

Lycopene-beta-cyclase

ξ-carotene desaturase

Daffodil gene

Single bacterial gene;

performs both functions

Daffodil gene

GoldenRice

Vitamin A Pathway is complete and functional

Construct of gene ceased

Biosynthesis of beta‐carotene in GM rice was accomplished by inserting phytoene synthase gene from daffodils (psy) and phytoene desaturase (ctrI) gene from the bacteria Erwinia uredovorainto rice DNA.

The latest… Syngenta Golden Rice - II (20 times more provitamin A) and

GM potatoes recently developed

Third generation Golden Rice using indica rice being tested (japonica variety used in other iterations unpalatable, produced much less vitamin A)

GE soybeans with omega-3 fatty acids (fish oil) in final stages of FDA approval (2010)

In 2011, First time plantings in India with Philippines and Vietnam But crop not yet adapted to local climates in developing countries

Antisense molecules Technology

GM plants with added nutrients ‐Strawberries

Strawberries, which are a good source of vitamin C, have been genetically modified to provide 3 times as much vitamin C.

A gene in the strawberry plant called GalUR gene codes for an enzyme that converts a protein in the plant to vitamin C.

A similar gene is found in the thale cress Arabidopsis thaliana.

Researchers created a DNA plasmid using the A. thalianagene and the bacteria Agrobacteriumand inserted into the strawberry plant to over‐express GalUR gene and produce 3 times as much vitamin C

More GM crops using noval gene -

• Currently, researchers around the world are working at creating and perfecting:Drought resistant wheat, corn, and rice

• Salt tolerant tomatoes

• Frost resistant strawberries

• Heat tolerant beans such as kidney, red, black, and pinto beans

• Carrots that produce a vaccine against hepatitis B

Genetic transfer to Non target species

The genetic transfer target species to non-target speciese by pollination via insect, wind, water and human being.

As a result create Super pest Super weedSuper species (Dominant)

Herbicide resistance improved crop Weeds related to crop(Same Spp)

Resistance gene transfer to weeds

Super weeds

Can’t destroy using weedicide

Pollination

X

Genetic transfer to Non target species

Super weeds ?

Super Pest ?

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References-Principles of Plant Genetics and Breeding - George Acquaah

Molecular plant breeding -Yunbi Xu

Plant Breeding – B. D. Singh

Biotechnology – H. S. Chwala

Shahal Abbo Plant domestication versus crop evolution Trends in Plant Science June 2014, Vol. 19, No. 6

Van DeynzeA. 2004. Roundup Ready Alfalfa: An Emerging Technology : anrcatalog.ucdavis.edu/pdf/8153.pdf

Brian Miki, Sylvia McHugh (2003), Selectable marker genes in transgenic plants: applications, alternatives and biosafety, Journal of Biotechnology 107 (2004) 193–232

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References-

Allard, R.W. (1976). Genetic basis of the evolution of adaptedness in plants. Euphytica 92, 1-11.

Cooper, H.D., C. Spillane and T. Hodgkin (2001). Broadening the genetic base of crop production, Published by: CABI, FAO and IPGRI, Rome. pp. 1-452.

Jones, Q. 1983. Germplasm needs of oilseed crops. Econ. Bot. 37: 418-422.

Rick, C.W. 1984. Plant Germplasm Resources. Pp. 9-37. In: D.A. Evens, W.R. Sharp, P.V. Ammirato and Y. Yamada (eds.). Handbook of Cell Culture, MacMillan, New York.

GM corn ‐http://www.geocities.com/veronicaguseva/cornGM.jpg

Roundup and untreated control ‐anrcatalog.ucdavis.edu/pdf/8153.pdf

Golden rice ‐http://en.wikipedia.org/wiki/Image:GoldenRice‐WhiteRice.jpg

Strawberries ‐http://en.wikipedia.org/wiki/Image:Strawberries.JPG