Title: In%20Vitro%20Selection
1 In Vitro Selection
Screen a large number of plants or cells for a
certain characteristics
2Definition Selection vs. Screening
- Selection
- 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 - The process determining the relative share
allotted individuals of different genotype in the
propagation of a population - The process by which certain organisms multiply
while other are less suited surrounding and die
out
3Definition Selection vs. Screening
- Screening
- An investigation of a large number of organisms
for the presence of a particular property - Use of a screen
- 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
4Selection
- The central step of the breeding process
- The success depends on the ease and speed with
which the superior plant within a segregating
population can be identified - In classical breeding, selection is carried out
on huge populations normally in the fields - Field selections are strongly influenced by
environmental condition - There are uncertain and lengthy, especially in
the case of breeding for quantitative
characteristics with a polygenic background
5Selection 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
6Selection
- 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
7Target of In vitro 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)
1. Leaf segment of young barley with standardized spore of powdery mildew (disease resistance) 2. Petiole culture of sugarbeet on salt enrichment media (mineral tolerance)
Selection of somaclonal variation (disease resistance, environmental tolerance) Selection using a selective agent (disease resistance, salt tolerance, metals tolerance, temperature stress tolerance, herbicide tolerance)
1. Selection for biotic stress resistance 2. Selection for a-biotic stress tolerance (cold, heavy metals, herbicide)
Quantitative trait loci Marker assisted Selection Marker assisted backcrossing
Organ
Tissue
Single Cells
DNA
8In vitro selection to heterogenous population
Screen large number of plant or cells for a
certain characteristics in sterile artificial
medium
- Certain characteristics
- Biotic stress resistance
- A-biotic stress tolerance
Applying selection agent (screening)
9Screening Agent
Characteristics Screening agent
Salt tolerance NaCl
Drought tolerance PEG
Mannitol
Sorbitol
Hydroxy-proline
Herbicide tolerance Related herbicide
Diseases resistance Pathogen culture filtrate
Phytotoxin Pathogen itself
10Types of selection methods
- Stepwise long term treatment
- Cultures are exposed to stress with gradual
increase in concentration of selecting agent - Shock treatment
- Cultures are directly subjected to a shock of
high concentration and only those which would
tolerate that level will survive
11The Advantage
- 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 - The ability to handle large numbers of
individuals in a very small space - The ability to work with the simpler genome of
which allows the uncovering of recessive traits
and additive characters within a relatively small
population - The ability to shorten the time of selection
- It can compliment field selection
12The disadvantage
- Loss of regeneration ability during selection
- Lack of correlation between the mechanism of
tolerance operating in the culture and those of
the whole plants - Phenomenon of epigenetics
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