Applications of Biotechnology in Plant Breeding

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22 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

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Applications of Biotechnology in

Plant Breeding

Sadanand Dhekney, PhD


University of Florida / IFAS

Mid
-
Florida Research & Education Center


Apopka, FL 32703


Limitations of Conventional Breeding




Extreme heterozygosity and pronounced
inbreeding depression in plant species





F1 hybrid produced is of intermediate quality




Long juvenile period of
sp.
makes screening of
new selections tedious and time consuming

Plant biotechnology

What is plant biotechnology?


Products on the market


Benefits of biotechnology


Plant biotechnology

A precise process in which scientific techniques

are adopted to develop useful and beneficial
plants.


Desired gene

Traditional plant breeding

DNA is a strand of genes,

much like a strand of
pearls. Traditional plant
breeding combines many
genes at once.

Traditional donor

Commercial variety

New variety

Desired Gene

X

=

(crosses)

(many genes are transferred)

Plant biotechnology

Using plant biotechnology,
a single gene may be
added to the strand.

Desired gene

Commercial variety

New variety

(transfers)

=

Desired gene

(only desired gene is transferred)

What is Plant Tissue Culture?


Totipotency


Single cell has the ability to regenerate into
a whole plant

What conditions do plant
cells need to multiply in
vitro?



Freedom from competition


Nutrients and removal of waste
products


A controlled environment

Applications

Seed culture



Increasing efficiency of germination of
seeds that are difficult to germinate in vivo



Precocious germination by application of
plant growth regulators


Production of clean seedlings for explants
or meristem culture

Embryo culture



Overcoming embryo abortion due to
incompatibility barriers


Overcoming seed dormancy and self
-
sterility of seeds


Embryo rescue in distant (interspecific or
intergeneric) hybridization where
endosperm development is poor


Shortening of breeding cycle


Ovary or ovule culture



Production of haploid plants


A common explant for the initiation of somatic
embryogenic cultures


Overcoming abortion of embryos of wide hybrids
at very early stages of development due to
incompatibility barriers


In vitro

fertilization for the production of distant
hybrids avoiding style and stigmatic
incompatibility that inhibits pollen germination
and pollen tube growth

Anther and microspore culture



Production of haploid plants


Production of homozygous diploid lines
through chromosome doubling, thus
reducing the time required to produce
inbred lines


Uncovering mutations or recessive
phenotypes

Organ culture


Any plant organ can serve as an explant to
initiate cultures

Shoot apical meristem culture



Production of virus free germplasm


Mass production of desirable genotypes


Facilitation of exchange between locations
(production of clean material)


Cryopreservation (cold storage) or

in vitro

conservation of germplasm

Somatic embryogenesis



One major path of regeneration


Mass multiplication


Production of artificial seeds


As source material for embryogenic
protoplasts


Amenable to mechanization and for
bioreactors

Embryogenic Culture System for
Vitis

Initiation from leaves on NB 2 medium (Gray, 1995)

Leaf explant

Embryogenic callus

Embryo development

Embryogenic

Non
-

embryogenic

Organogenesis



One major path of regeneration


Mass multiplication


Conservation of germplasm at either
normal or sub
-
zero temperatures

Callus Cultures



In some instances it is necessary to go through
a callus phase prior to regeneration via somatic
embryogenesis or organogenesis


For generation of useful somaclonal variants
(genetic or epigenetic)


As a source of protoplasts and suspension
cultures


For production of metabolites


Used in i
n vitro

selection

Initiation from Stamens and Pistils

Embryogenic callus

Callus formation from

connective tissue

Callus formation from

filament tip

Embryo development

Embryo germination

Stamen explant

In vitro mutagenesis



Induction of polyploidy


Introduction of genetic variability

Genetic transformation



Introduction of foreign DNA to generate
novel (and typically desirable) genetic
combinations

Many different explants can be used,
depending on the plant species and its
favored method of regeneration as well as
the method of transformation


Used to study the function of genes

Genetic Transformation System


Regenerate transgenic

plants

Co
-
cultivate

48 h

+

Wash explants


Agro culture

Callus induction

medium

Select transgenic embryos

using GFP/NPT II system

Embryo development

medium

Embryo explants

Applications


Disease resistance


Insect resistance


Salinity tolerance


Heavy metals tolerance


Improved nutritional characteristics


More than 50 biotech food products
have been approved for commercial
use in the United States


Canola (5%)


Corn (21%)


Cotton (12%)


Papaya


Potato


Soybeans (62%)


Squash


Sugarbeets


Sweet corn


Tomato

Advantages & Limitations

Advantages


Food quantity


Food quality


Eco friendly



Limitations


Recent scientific advances


Tangible benefits may not be long term