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ROYAL UNIVERSITY OF BHUTAN
SHERUBTSE COLLEGE
KANGLUNG: BHUTAN
Name: Dawa Tshering
Programme: B
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Life Science
Assignment No: 1
Enrolment No: 07180321
Semester: 5th
Due date: 08/12/2020
Module: BTS306
Submission date: 08/12/2020
Submitted to: Mr
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Chettri
I have read and understood the definition of academic dishonesty as given in the Wheel of Academic Law, RUB,
which is reproduced on the backside of this cover page
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I understand that if found
otherwise, my assignment is likely to be cancelled
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Organization,
structure and
language use
2
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Scientific
research
information
4
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Submission
Signature of Module Tutor
1
Marks
awarded
Criteria for Marking
Max
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1
Contents
Introduction
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3
History of Selection
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5
Procedure for Pure line selection
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6
Second year
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6
Fourth year
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6
Pure-line Selection characteristic
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8
Applications of the pure-lines selection
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9
Conclusion
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11
2
Introduction
3
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This is accomplished by creating various
methodology
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In
unadulterated line determination, improvement of the assortment is exceptionally uniform with the
inclusion of a solitary plant
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Unadulterated line choice is tedious concerning
the improvement of the assortment when contrasted and the mass choice (Samanthi R
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In
the early twentieth century, Wilhelm Johannsen proposed his pure-line theory and the
genotype/phenotype distinction work that is prized as one of the most important founding
contributions to genetics and Mendelian plant breeding
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Instead, breeding
becamemoreorderlyasaconsequenceofpurelinetheorywhichstructuredbreedingprogrammesandeli
minatedexternal heritable influences
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, 2017)
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Improvement of
new assortment through identification and confinement of single best plant descendants is known
as unadulterated line choice
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So
Pure line is an enormous number of plants are chosen from self-pollinated crops and are gathered
exclusively
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During the pure line selection process, a large quantity of selfpollinating crop plants is selected and harvested individually
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Since this procedure involves a single crop variety, it is also referred to as individual plant
selection
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Phenotypic differences present within the plants of pure line are
environmental and will not transfer to the next generation
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Pure line plants can
be utilized in order to develop new varieties by hybridization
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The pure line selection
mainly includes three steps; selection of plants (source of mixed population, evaluation of the
progeny and yield trials
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, 2017)
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nana to perform a series of experiments
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The selection of a pure line corresponds to the process of separation of pure line of an
original mixed population
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Individuals of a pure line have the same genotype
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Due to the previous point, the selection within a pure line is not effective
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Variations that appear within a pure line are due to environmental factors
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Present day, all varieties of self-pollinated crops are pure-lines
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According
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Local varieties
2
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Introduced varieties
The pure-line selection has three steps for evolving a variety
1
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2
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Yield trials
History of Selection
The history of plant selection goes back to ancient times where it was practiced by the farmers
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In the year 1843, Le coutier, a farmer
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of island of New Jersey published his results on selection in wheat and he concluded that the
progenies from single plants were more uniform
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In 1857, Hallet in
England, developed several commercial varieties by practicing single plant selection in wheat oats
and barley (Savitha, 2018)
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This method was successful in sugar beet but not in other
cross-pollinated crops
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The
basic steps in every breeding method is progeny testing (Savitha, 2018)
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He conducted
experiment on the plant Phaseolus vulgaris which is a species that self-pollinates
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Progenies of larger seeds produced
larger seeds and progenies from smaller seeds produced small seeds only
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He studied nineteen lines altogether and
concluded that in market lot of the beans supplied are the mixture of pure lines
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1
whatever variation observed within a line is due to environment factor only (Berry, 2014)
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In line 13, which is having 450 mg seed
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Ultimately, he got lines having weight ranging from 458 to 475
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The second evidence was that selection with a pure line is ineffective
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After six generations of selection, the line for large seed as well as for small seed gave progenies
having 680-690 mg and it did not change further
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In third evidence, when parent-off spring regression was worked in line thirteen
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found be to zero indicating that variation observed is nonheritable and it is due to environment
only
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Procedure for Pure line selection
First year
6
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The single plant is selected and harvested separately and superior plants must be selected
from the mixed population
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Second year
The individual progenies are grown separately with proper spacing
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Poor, defective, weak and segregating progenies are discarded
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This process may be repeated
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So, they are
grown in unreplicated trial with check
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Fourth year
Replicated yield trials are conducted using the best available check variety
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Fifth to Eighth year
Promising strains are evaluated at several locations along with strains or check
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6
7
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Retrieved from: https://plantlet
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Used in self-pollinated species
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Genetic variation is absent
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Production of variety is highly uniform
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All the plants within a pure-line have the same genotype
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5
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So, selection
within pure line is not effective
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Pure lines become genetically variable with time
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7
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Uses of pure-Line selection
Some of the uses of pure lines are:
1
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Almost all the varieties of selfpollinated crops are pure line
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As a parent in a hybridization programme hybridization invariably based on pure line
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4
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5
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Applications of the pure-lines selection
Some of the applications of pure-line selections according to Fernandes (2016) are:
1
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2
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3
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4
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5
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8
Pure line selection and Mass selection
1
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The new variety is a mixture of pure-lines
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In fact, the variation within a pure-line variety is purely environmental
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2
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Progeny test is generally not carried out
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The variety is generally the best pure-line present in the original population
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The variety is
inferior to the best pure-line because most of the pure-lines included in it will be inferior
to the best pure-line
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Generally, a pure-line variety is expected to have narrower adaptation and lower stability
in performance than a mixture of pure-lines
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5
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It is not necessary they should have a similar
phenotype
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6
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If a large number of plants are selected, expensive yield trials are not necessary
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9
Conclusion
The pure line selection method depends on the knowledge that continued selfing of a heterozygous
individual or population of a self-pollinated plant species will result in an increasing proportion of
the subsequent population becoming homozygous
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In crop breeding the parents of a cross usually differ by a large number of gene pairs and this
number will influence the number of generations of self-fertilisation necessary for the hybrid
population to reach homozygosity
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The degree of homozygosity of
the hybrid population depends on the number of independent gene pairs by which the parents differ
and the number of generations of selfing since hybridisation
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(2014)
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Studies in History and Philosophy of Science Part C:
Studies in History and Philosophy of Biological and Biomedical Sciences, 46, 25-37
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E
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Mass and line selection can produce ewually uniform rice varities
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016/j
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2006
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009
Samanthi, R
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Comparing the riskiness of dependent portfolios via nested l-statistics
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Savitha, S
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A study on the production and marketing of horticulture crops in
nagapattinam district–tamil nadu
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, 5(2), 62-66
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1
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Atleast 5 different references to be used for writing your intro part, otherwise have no different points here!
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Cite figure here too!
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Could have added more references!