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Triploidy ...............................pptx

The document discusses triploidy, a genetic condition in plants characterized by three sets of chromosomes, leading to advantages such as larger organ size, increased biomass, and seedless fruit production. It highlights the methods of producing triploid plants, including endosperm culture and hybridization, as well as their applications in horticulture and agriculture. Additionally, it outlines both the benefits and limitations of triploid plants, along with references for further reading.

Science◦
TRIPLOIDY 1
Content 1. Triploidy 2. Importance of triploid plants 3. Conventional production of triploid plants 4. Endosperm culture 5. Advantages 6. Limitations 2
TRIPLOIDY • Triploidy is a genetic condition characterized by the presence of three sets of chromosomes in an organism’s cells instead of the usual two. • Triploid plants have larger organs, greater biomass, and strong stress resistance by preserving relatively larger amounts of photosynthetic energy. • Triploid plants are valued for the seedless fruits. E.g., seedless banana, watermelon etc. Triploidy… 3
Importance of triploid plants Seedless Fruit Production • One of the primary applications of triploidy in plants is the production of seedless fruits. • For example, seedless watermelons, grapes, and bananas are often triploid varieties. Triploidy… 4
Increased Vigor and Growth • Triploid plants are typically sterile, meaning they cannot produce viable seeds. • This sterility is advantageous in fruit production, as it eliminates the need for seeds, enhancing the fruit’s market value and desirability. Neutralizing invasive plants • The undesirable spread of non-native invasive crop and horticultural plants into natural areas can also be reduced or eliminated by the use of triploids, because they tend to be sterile and seedless. Triploidy… 5
• Triploid production increases the size of somatic cells and guard cells and increases chloroplast number, which results in strengthening photosynthesis. • Therefore, many triploid plants are relatively more vigorous; have short internodes; broad, thick, dark green leaves, resulting in greater biomass or crop yield per plant. Triploidy… 6
Prolonging flowering period • Flowers of triploid plants are generally larger and more colorful than those of their diploid counterparts partly because the energy that is normally devoted to seed formation is used for flowers or other organs. • Triploid flowers often have longer shelf life. Genetic Research • Studying triploid plants provides valuable insights into genetics and chromosomal behavior. • Understanding how triploidy influences gene expression and development can contribute to broader advancements in plant genetics. Triploidy… 7
• Some triploid plants demonstrate improved resistance to certain diseases. • Triploid plants may exhibit enhanced tolerance to environmental stresses such as drought, heat, or soil salinity. This resilience makes them well-suited for cultivation in challenging conditions. • Triploid plants can result from crossing two different diploid varieties. The hybrid vigor, or heterosis, observed in triploid offspring often leads to plants with superior qualities, including better disease resistance, adaptability, and overall robustness. Triploidy… 8
• Triploid plants often exhibit enhanced fruit quality. • This is of great value in tree species, which are grown for biomass production such as acacia, sandalwood and Tea. • Triploid plants are used in ornamental horticulture to create new and unique flower varieties. Triploidy… 9
Conventional production of Triploid plants Natural selection • Fertilization of unreduced gamete (2x) with the normal gamete (n) results in triploids. • Environmental stress variables may stimulate production of unreduced gametes in diploids. • Rare in nature because of inviable seeds and hence no progeny. • Banana is a typical example of naturally existing triploid. Triploidy… 10
• Triploidy is encountered occasionally in natural populations of flowering plants containing diploid (2n) and tetraploid (4n) plants. • Triploids arise by natural crosses between diploid and tetraploid plants in the same population. • However, there are many examples of triploid strains of cultivated plants that have been induced artificially by crossing diploid and tetraploid parental strains. Triploidy… 11
Artificial hybridization • Sexual hybridization of diploid and tetraploids is the most common method i.e. 2x X 4x or 4x X 2x. • Chromosome doubling can be achieved by spindle inhibitors or protoplast fusion. • Colchicine is commonly used to disrupts spindle fiber formation during cell division, leading to chromosome doubling in treated cell. Triploidy… 12
• The diploid plants are treated with colchicine to get tetraploid plant (4n). • The tetraploid and diploids are crossed. • Thus triploid plant was formed. • Triploid efficiency depends upon several factors like Pollen viability, compatibility between the parents or the frequency of unreduced gametes. Triploidy… 13
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Endosperm culture • Culture of endosperm to regenerate whole plants under in vitro condition is termed as endosperm culture. • Endosperm is formed in most cases by the fusion of two polar nuclei with one of the male gamete. • It is the main source of reserve food for the developing embryo. Triploidy… 16
Endosperm • Short lived • Unorganized • Triploid • Stores reserve food materials • Provides nutrition during embryo development and seed germination Triploidy… 17
• Endosperm is generally short lived-structure and is consumed during the development of embryo (exalbuminous seed). • In plants like Castor, it exists as a massive tissue even in the mature seed (albuminous seed). • Seedless triploid plants can be produced by endosperm culture. • The first attempt on endosperm culture was made by La Duel (1949). Triploidy… 18
TYPES OF ENDOSPERM CULTURE 1. Mature endosperm culture It is the in vitro development of isolated mature endosperm from ripen endospermic seed on suitable culture medium to obtain triploid plantlet is called mature endosperm culture. 2. Immature endosperm culture It is the in vitro development of isolated immature endosperm isolated at precise stage from immature seed, cultured on suitable culture medium to obtain triploid plantlet is called immature endosperm culture. 19
STEPS IN ENDOSPERM CULTURE • It consist of mainly 3 steps: 1. The immature or mature seeds are dissected under aseptic conditions and endosperms along with embryos are excised. 2. Excised endosperms are cultured on a suitable medium and embryos are removed after initial stage. 3. Callus followed by embryogenesis or shoot bud differentiation. 4. Complete plant formation. Triploidy… 20
1. Explant source • In most of the cereals, mature endosperm does not respond to cultural conditions. It is therefore, excised at proper period of development. • In some families association of embryo tissue in initial stages seems essential for proliferation of mature endosperm. In such cases, entire seeds are used as explant. Immature seeds provide explant for non- endospermic seeds.
2. Inoculation of explant • For in vitro culture mature endosperm, seeds having massive endosperm are decoated, surface sterilized with suitable disinfectant and after 2-3 washings with sterile distilled water, planted on the nutrient medium. • For in vitro culture of an immature endosperm, the entire seed or kernel is surface sterilized and the endosperm tissue is excised under aseptic conditions. In cereals, top of kernel or immature ovaries (micropyle end) are cut off with a sterile knife and exposed endosperm squeezed out and placed on the callus induction nutrient medium. • The basal medium is supplemented with tomato juice, yeast extract, grape juice. Sucrose (2-4%) is used as a source of carbohydrates. In some cases, addition of 2,4- D or IAA, cytokinin necessary.
3. Incubation/ maintenance of culture To induce callus, the endosperm cultures are maintained darkness or diffused light. Differentiation take place when calli are transferred to bright light (2000 lux – 4000 lux) and 25°C temperature 4. Shoot bud differentiation or embryogenesis • Plantlet formation from endosperm callus maturation follow organogenic or embryogenic mode of development. • Embryo differentiation occurs when the proliferated tissue is transferred from callusing to basal medium with or without gibberellins. So culturing carried out up to complete development of plantlet. 5. plantlet developed are hardened in green house by transferring in vermiculture media and maintaining proper humidity.
Triploidy…
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Advantages 1. A novel method for triploid plant production • This technique has enabled the production of triploid plants. Triploid plants are self sterile and usually seedless. • Endosperm culture technique is applied to economically important cultivars for raising superior triploid plants. • The trait increases the edibility of fruits. • E.g., Apple, Banana, Mulberry, Sugar beet, Peach, Watermelon etc., which are commercially important for their edible parts. Triploidy…
2. Increases yield of timber and fuel • In timber and fuel yielding plants, triploids show better performance over their relative diploids and tetraploids. 3. Rescuing embryos from incompatible crosses • The most useful and popular application of embryo cultures is to raise rare hybrids by rescuing embryos from incompatible crosses. 4. Overcoming dormancy and shortening breeding cycle • Long, periods of dormancy in seeds delay breeding works, especially in horticultural and crop plants. Using embryo cultures techniques the breeding cycle can be shortened in these plants. Triploidy…
5. Overcoming seed sterility • In early ripening fruit cultivars, seed do not germinate because their embryos are still immature. • Using the embryo culture method it is possible to raise seedling from sterile seeds of early ripening stone fruits, peach, apricot and plum. 6. To exploit in the biosynthesis of some natural products. E.g.:- Cultured endosperm of coffee synthesizes caffeine. The level of this alkaloid in callus is synthesized by three times after two weeks and by 6 times after 4-5 weeks. 7. Various trisomic developed from triploids may also be useful in gene mapping for cytogenetic studies. Triploidy…
Limitations 1. Triploid production through endosperm culture technique has been successful only in a limited number of species. In majority of species mature endosperm proliferation resulted in a callus tissue of unlimited growth. But the induction of organogenesis in endosperm culture has always being a challenging problem. 2. In cereals (or) crops where grains (or) seeds are used, triploids are undesirable. Triploidy…
Reference 1. Bhojwani, S. S., & Razdan, M. K. (1986). Plant tissue culture: theory and practice. Elsevier. 2. De K.K. (2003). Plant Tissue Culture. New Central Book agency (P) Ltd, Calcutta. 3. Razdan M.K. (2000). An introduction to plant tissue Culture. Oxford& IBH publishing Co. Pvt. Ltd. New Delhi, Calcutta. 4. Wang, X., Cheng, Z. M., Zhi, S., & Xu, F. (2016). Breeding triploid plants: a review. Czech Journal of Genetics and Plant Breeding, 52(2), 41-54. 5. https://www.ehow.com/info_12013003_triploid-plants.html
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