Haploid is applied to any plant originating from a sporophyte (2n) and containing (n) number of chromosomes.
Artificial production of haploids was attempted through distant hybridization, delayed pollination, application of irradiated pollen, hormone treatment and temperature shock.
The artificial production of haploids until 1964 was attempted through:
1. Distant hybridization
2. Delayed pollination
3. Application of irradiated pollen
4. Hormone treatments
5. Temperature shocks
The development of numerous pollen plantlets in anther cultures of Datura innoxia, first reported by two Indian scientists (Guha and Maheshwari, 1964, 1966), was a major breakthrough in haploid breeding of higher plants.
The technique of haploid production through anther culture ('anther - androgenesis') has been extended successfully to numerous plant species, including many economically important plants, such as cereals and vegetable, oil and tree crops.
3. INTRODUCTION
ο The term haploid refers to those plants which possess a
gametophytic number of chromosomes single set in their
sporophytes.
ο Artificial production of haploids was attempted through
distant hybridization, delayed pollination, application of
irradiated pollen, hormone treatment and temperature shock.
ο Haploid plants are of great significance for the production of
homozygous lines (homozygous plants) and for the
improvement of plants in plant breeding programme.
ο Haploid is applied to any plant originating from a sporophyte
(2n) and containing (n) number of chromosomes.
4. Haploids are broadlydivided into two categories
ο Monoploids (monohapioids):- These are the
haploids that possess half the number of
chromosomes from a diploid species e.g. maize,
barley.
ο Polyhaploids:- The haploids possessing half the
number of chromosomes from a polyploid species
are regarded as polyhaploids e.g. wheat, potato.
5. TECHNIQUE
ο Androgenesis:-
Haploid production occurs through anther or pollen
culture, and they are referred to as androgenic
haploids.
ο Gynogenesis:-
Ovary or ovule culture that results in the production
of haploids, known as gynogenic haploids.
6. ANDROGENESIS
ο The androgenic method of haploid production is
from the male gametophyte of an angiosperm
plant, i.e. microspore (immature pollen).
ο The principle is to stop the development of
pollen cell whose fate is normally to become a
gamete, i.e. a sexual cell, and to force its
development directly into a plant.
ο Haploids can be obtained by the culture of
excised anthers and culture of isolated pollen
(microspore).
7.
8. FACTOR AFFECTING ANDROGENESIS
ο Physiological status of the donor plants
ο Stage of pollen development
ο Anther wall factor
ο Genotype
ο Pre-treatment of cultured anther/pollen grains
ο Culture medium
ο Culture density
ο Effect of gaseous environment
ο Effect of light
9. GYNOGENESIS
ο Development of plants from unfertilized cells of
the female gametophyte (embryo sac), in floret,
ovary or ovule culture.
ο It was first reported in barley by San Noeum
1976
ο The gynogenic plants may arise through direct
embryogenesis, or the gametic cells may form a
callus followed by plant regeneration on another
medium.
10.
11. FACTOR AFFECTINGgynoGENESIS
ο Explant
ο Pretreatment
ο Culture medium
ο Genotype
ο Embryo sac stage
ο Seasonal effect
ο Physical factor
ο Stage of harvest of ovule
ο Growth condition of donor plant
12. APPLICATIONOF HAPLOIDPRODUCTION
ο Development of pure homozygous lines
ο Developing asexual lines of trees/perennial species
ο Hybrid development
ο Induction of mutation & genetic variability
ο Cytogenetic research
ο hybrid sorting in haploid breeding
ο Disease, insect, salt resistance
ο Doubled haploid in genome mapping
ο Significance in early release of varieties
ο Generation of Exclusively Male Plants and a few
others
13. PROBLEMS
ο Production of gynogenic haploids through female
gametophyte still needs more refinement and also there
are problems in dissection of unfertilized ovules and
ovaries.
ο High level of management and expertise is required to
operate the tissue culture production of haploids.
ο Diploids and tetraploids often regenerate at the same
rate as the haploids.
ο Selective cell division must take place in the haploid
microspores and not in other unwanted diploid tissues.
ο The lack of selection of traits during the derivation of
haploid material.
ο The doubling of a haploid does not always result in the
production of a homozygote.