Transcript In Vitro Screening "The right to search for truth implies also a duty; one must not conceal any part of what one.

In Vitro Screening
"The right to search for truth implies
also a duty; one must not
conceal any part of what one has
recognized to be true."
Albert Einstein, 1879-1955
"The right to search for truth implies
also a duty; one must not
conceal any part of what one has
recognized to be true."
Albert Einstein, 1879-1955
Definition:
Selection vs Screening
Selection:
1. The process by which some individuals come to
contribute more offspring than others to form the next
generation through intrinsic difference in survival and
fertility or the choice of parent by the breeder
2. The process determining the relative share allotted
individuals of different genotype in the propagation of a
population
3. The process by which certain organisms multiply while
other are less suited surrounding and die out
Definition:
Selection vs Screening
Screening:
1. An investigation of a large number of organisms for the
presence of a particular property
2. Use of a screen
3. Examining the properties, performance response of
individuals, lines, genotypes or other taxa under an
assortment of condition in order to evaluate the
individuals or groups
Selection
1. The central step of the breeding process
2. The success depends on the ease and speed with
which the superior plant within a segregating
population can be identified
3. In classical breeding, selection is carried out on
huge populations normally in the fields
4. Field selections are strongly influenced by
environmental condition
5. There are uncertain and lengthy, especially in the
case of breeding for quantitative characteristics
with a polygenic background
Selection methods
The most common breeding procedure was mass-selection which in
turn was subdivided into negative and positive
 Negative selection
The most primitive and least widely used method which can lead to
improvement only in exceptional cases
implies culling out of all poorly developed and less productive
individuals in a population whose productivity is to be genetically
improved
The remaining best individuals are propagated as much as necessary
 Positive selection
Only individuals with characters satisfying the breeders are selected from
population to be used as parents of the next generation
seed from selected individuals are mixed, then progenies are grown
together
Production and
Use of Variability
1.Conventional breeding
 Combination Breeding (Cross Breeding)
 Mutation Breeding
 Chromosome transfer (wide hybridization)
2. Modern breeding
 Cell fusion
 Soma-clonal Variation
 Gene transfer
Selection
1. On the whole plant
 Field trials
 Green-house trials
 Laboratory trials (in vitro selection)
2. On the simple genome (in vitro selection)
 Haploid selection
 Single cell selection
 DNA probes
The Advantage of
In-vitro Selection
1. Freedom from the effect of climate and natural
environment, which make it easier to measure slight
difference in polygenic inherited traits horizontal or
general disease resistance
2. The ability to handle large numbers of individuals in a
very small space
3. The ability to work with the simpler genome of which
allows the uncovering of recessive traits and additive
characters within a relatively small population
Target of Invitro Selection
Whole plant
(Seed/embryo)
1. Seedlings of a culture filtrate from Leptosphaeria
masculans (disease resistance)
2. Rice seedlings of salt enrichment media (Mineral
tolerance)
Organ
1. Leaf segment of young barley with standardized spore of
powdery mildew (disease resiantance)
2. Petiole culture of sugarbeet on salt enrichment media
(mineral tolerance)
Tissue
1.
2.
Single Cells
DNA
Selection of somaclonal variation (disease resistance,
environmental tolerance)
Selection using a selective agent (disease resistance, salt tolerance,
metals tolerance, temperature stress tolarence, herbicide tolerance)
1. Selection for biotic stress resistance
2. Selection for a-biotic stress tolerance (cold, heavy
metals, herbicide)
1. Quantitative trait loci
2. Marker assisted Selection
3. Marker assisted backcrossing
It would emphasize here the necessity of growing
all in vitro selected plants in the field
Very often a powerful in vitro tolerance does not
show up at the whole plant level under field
condition