Haploid Production - Techniques, Application & Problem
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The document discusses haploid production in plants, emphasizing its importance for generating homozygous lines and improving plant breeding. It outlines techniques such as androgenesis and gynogenesis, detailing factors affecting each method and their applications in hybrid development, mutation induction, and disease resistance. Challenges in haploid production, including the need for high management expertise and complications in maintaining selective cell division, are also highlighted.
Haploid Production - Techniques, Application & Problem
- 2. OVERVIEW Introduction Categories of haploid Technique involved in haploid production Androgenesis Gynogenesis Applications Problems
- 3. INTRODUCTION The term haploid refers to those plants which possess a gametophytic number of chromosomes single set in their sporophytes. Artificial production of haploids was attempted through distant hybridization, delayed pollination, application of irradiated pollen, hormone treatment and temperature shock. Haploid plants are of great significance for the production of homozygous lines (homozygous plants) and for the improvement of plants in plant breeding programme. Haploid is applied to any plant originating from a sporophyte (2n) and containing (n) number of chromosomes.
- 4. Haploids are broadlydivided into two categories Monoploids (monohapioids):- These are the haploids that possess half the number of chromosomes from a diploid species e.g. maize, barley. Polyhaploids:- The haploids possessing half the number of chromosomes from a polyploid species are regarded as polyhaploids e.g. wheat, potato.
- 5. TECHNIQUE Androgenesis:- Haploid production occurs through anther or pollen culture, and they are referred to as androgenic haploids. Gynogenesis:- Ovary or ovule culture that results in the production of haploids, known as gynogenic haploids.
- 6. ANDROGENESIS The androgenic method of haploid production is from the male gametophyte of an angiosperm plant, i.e. microspore (immature pollen). 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. Haploids can be obtained by the culture of excised anthers and culture of isolated pollen (microspore).
- 8. FACTOR AFFECTING ANDROGENESIS Physiological status of the donor plants Stage of pollen development Anther wall factor Genotype Pre-treatment of cultured anther/pollen grains Culture medium Culture density Effect of gaseous environment Effect of light
- 9. GYNOGENESIS Development of plants from unfertilized cells of the female gametophyte (embryo sac), in floret, ovary or ovule culture. It was first reported in barley by San Noeum 1976 The gynogenic plants may arise through direct embryogenesis, or the gametic cells may form a callus followed by plant regeneration on another medium.
- 11. FACTOR AFFECTINGgynoGENESIS Explant Pretreatment Culture medium Genotype Embryo sac stage Seasonal effect Physical factor Stage of harvest of ovule Growth condition of donor plant
- 12. APPLICATIONOF HAPLOIDPRODUCTION Development of pure homozygous lines Developing asexual lines of trees/perennial species Hybrid development Induction of mutation & genetic variability Cytogenetic research hybrid sorting in haploid breeding Disease, insect, salt resistance Doubled haploid in genome mapping Significance in early release of varieties Generation of Exclusively Male Plants and a few others
- 13. PROBLEMS Production of gynogenic haploids through female gametophyte still needs more refinement and also there are problems in dissection of unfertilized ovules and ovaries. High level of management and expertise is required to operate the tissue culture production of haploids. Diploids and tetraploids often regenerate at the same rate as the haploids. Selective cell division must take place in the haploid microspores and not in other unwanted diploid tissues. The lack of selection of traits during the derivation of haploid material. The doubling of a haploid does not always result in the production of a homozygote.