Plant
Breeding
What is Plant Breeding?
ð
Plant breeding is an art and science, which tells
s ways and means to change the genetic architecture of plants a particular
objective.
ð
Plant breeding can be accomplished through many
different techniques ranging from simply selecting plants with desirable
characteristics for propogation.
ð
International development agencies believe that
breeding new crops is important for ensuring food security by developing new
varieties that are higher- yielding, pest resistance and disease, drought
resistance or adapted to different environment and growing conditions.
Objectives of Plant Breeding /-
ð Crop
improvement
ð Improved
agronomic characters
ð Resistance
against and biotic stress
· Increased yield /- majority of breeding aims at
increased yield. This is achieved by developing more efficient genotypes.
· Elimination of toxic substance like HCN
content in Jowar plant.
· Resistance against Biotic and Abiotic stress
/-
Biotic stress - Evolving pests and disease resistant
varieties there by reducing cost of cultivation, and env. pollution and saving
beneficial insects.
Abiotic Stress – it is location specific
problem. Soil factors and edaphic factors some times poses severe problems.
Breeding resistant varieties is the easy way to combat abiotic stress.
· Change in maturity – early
maturity varieties.
· Improved Agronomic characters- Production
of more tillers. Eg rice , Bjara.
· Reduce plant height to prevent lodging - rice.
Scope of Plant Breeding /-
Since the cultivation of land is
shrinking and there is no scope for increasing the area under cultivation, the
only solution is to required the increasing crop yield through the genetic
variation improvement of crop plants.
There are two ways which is
possible. –
ð Enhancing the productivity of crop-
This can be done by proper management of soil
and crops involving suitable agronomic practices.
By using higher potential crop varieties
created by genetic manipulation of crop plants.
ð Stabilizing the productivity achieved –
This done by using crop varieties that are
more adaptation for specific crop zones to off set the ill effects and others.
What is Emasculation ?
ð It is the
process of removing of anther from the bisexual flowers without affecting the
female reproductive part of the flower (pistil), which is used in various
hybridization of plant technique.
ð Emasculation
is performed in bisexual flower to obtain the desired varieties of a plant by
crossing a particular plant with the desired pollen grains.
Emasculation
& Crossing techniques :-
· Emasculation
is necessarily followed by controlled pollination. The following methods are
widely used for hybridization in rice.
1.
Clipping Method
2.
Hot water Method
3.
Vacuum Emasculation method
4.
Cuttack method
5.
Brown paper Method
6.
Rhind’s method
What is Selfing ?
The inflorescence is
covered with a butter paper cover prior to anthesis, and kept undisturbed till
the flower opening completed.
What is Crossing ?
In Plant breeding a crossing is natural process occur when
pollen is transfer from one plant to another plant.
Apomixis /-
ð Apomixis,
derived from two greek word “APO” (away from ) and mixis” (act of mixing or
mingling).
ð It refers
to the occurrence of an sexual process in the place of normal sexual processes
involving reduction division and fertilization.
ð OR it is
a type of reproduction in which sexual organs of related strucutres take part
by seeds are formed without union of
gametes. Seeds are formed are vegetative in origin.
ð Winkler
(1908) defined apomixes as “the substitution for sexual reproduction or another
asexual reproductive process that does not involve nuclear and cellular fusion.
(fertillisation)
Types of
apomixes – s
Mainly four types of Apomixis are suggested by maheshwari
(1954).
1.
Recurrent apomixes
2.
Non – recurrent apomixes
3.
Adventive embryony
4.
Vegetative Apomixis
Advantages
of Apomixis –
ð Assured
reproduction in plant breeding in absence of pollinators, such as in extreme
environments.
ð Maternal
energy is not wasted in unfit offspring.
ð Some of
the apomictic plants can avoid the male energy cost of producing pollen.
Some of
the disadvantages of Apomixis :- s
ð Accumulation
of harmful mutation may occur
ð Lack
ability to adapt the change in
environment.
Maize
(zea
mays) (2n=20)
Family :-
Poaceae
ð Maize is
predominantly cross pollination.
ð Wind
(Anemophily) is the general rule.
ð Pollination
by insects also takes place to content extent.
Selfing –
Bag the tessel before the anthesis with a butter paper cover.
Cut the tip of the cob before the silk is emerging and cover
with the paper cover. After 3-4 days the silk will emerge in the form a ‘saving
brush’ in which the silk will be the same height and stand erect.
Remove the cover of tassel containing pollen and insert it
over the cob- cover. The inserted covered is tied then.
Crossing
Technique –
Female
parent
a.
Detassel
b.
Cut the tip of the cob before emerging the silk
and cover with the butter paper.
Male parent
a.
Cover the tassel before the anthesis begin and
soon as the tassel emerges.
Emasculation
Techniques used –
ð Hand
Emasculation
ð Hot water
Method
ð Plastic
bag/ mass emasculation technique
Pearl Millet
Cumbu
(Bajra) (Pennicetum glacum)
2n = 14
Family – Poaceae
ð Cumbu is
naturally cross pollinated (Allogamous).
ð Wind is
the chief agent of the pollination (anemophily).
ð
