👨‍❤️‍💋‍👨Method of Propagation

👉🏻 Plants can be propagated by sexual and asexual means. Understanding both methods is essential, as each has specific advantages and limitations that determine which method is best suited for a given crop.

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Sexual Methods of Propagation

• Propagation or multiplication of plants by seeds is known as ‘sexual propagation’. Seeds are formed as a result of successful fertilisation and combination of parental gametes. Since seeds are the product of fusion of male and female gametes, the resulting progeny carries genetic material from both parents, leading to variation.
• It is an old and easy method and is widely used for the propagation of crops like ornamental annuals, vegetables, medicinal and fruit plants, such as papaya. For crops where genetic uniformity is not critical or where varietal improvement is desired, seed propagation is the preferred method.

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Merits of sexual propagation

• Plants propagated by seeds live longer, are vigorous and more resistant to biotic (insect-pests and diseases) and abiotic stresses (environmental conditions). Seedling plants develop a strong, deep tap root system which anchors them firmly and allows them to access water and nutrients from deeper soil layers.
• It is an easy, simple and convenient method of plant propagation. Minimal skill and equipment are required compared to vegetative methods like grafting and budding.
• Some plants like papaya, marigold, chilli, capsicum, tomato, etc., cannot be propagated by asexual method. For these crops, seed propagation is the only option available.
• It is the only means of creating genetic diversity of plants. Genetic recombination during sexual reproduction creates new combinations of traits that can be selected for desirable characteristics.
• New varieties and cultivars of ornamental and vegetable crops can be developed only by this method. Plant breeding programmes rely entirely on sexual reproduction through hybridization and selection.
• A large number of rootstocks for budding and grafting purpose is also raised by this method. Rootstocks for most fruit crops are raised from seeds before the desired scion variety is grafted or budded onto them.
• Seeds can be transported easily and stored for a longer time using this method. Seeds are lightweight, compact, and can be stored under proper conditions for extended periods, making them ideal for distribution over long distances.

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Demerits of sexual propagation

• Sexually propagated plants show variations and are not genetically true-to-type to the mother plants. Due to genetic segregation and recombination, seedlings differ from the parent plant, which is undesirable when uniformity is needed for commercial production.
• Plants that are propagated through seeds have long gestation period, which results in delayed flowering and fruiting. Seedling trees take many years to reach the reproductive stage — for example, a mango seedling may take 6-10 years to bear fruit, compared to only 3-4 years for a grafted plant.
• Plants grow vigorously and cause obstruction in intercultural practices like harvesting and spraying. The tall, vigorous growth of seedling trees makes them difficult to manage in modern orchards.
• Advantages offered by rootstocks and scion as in asexual propagation cannot be exploited through sexual method. The benefits of combining a disease-resistant or dwarfing rootstock with a high-quality scion variety are unique to asexual propagation.
• Crop species, which do not produce seeds like pineapple, banana, strawberry, fig, jasmine, hibiscus, bougainvillea, etc., cannot multiply by this method. These crops are either seedless or produce non-viable seeds, making vegetative propagation the only option.

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Seed

• Seed quality is considered best if pure seed % is above 98%. Moisture content: 6-8% Germination %: 60-70%. These are the standard seed quality parameters that ensure good establishment in the nursery. High purity means minimal weed seeds and other crop seeds, while proper moisture content ensures seed viability during storage.

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Dormancy

• Inability of viable seed to germinate. Seed dormancy is a natural mechanism that prevents seeds from germinating under unfavourable conditions, ensuring the species’ survival. However, it can be a challenge for growers who need seeds to germinate promptly.
• Hard seed coat dormancy: Ber, Guava, Walnut. In these crops, the seed coat is so hard and impermeable that water and oxygen cannot enter, preventing germination.
• Dormancy due to presence of ABA — temperate fruits. Abscisic acid (ABA) is a plant hormone that inhibits germination. Temperate fruit seeds contain high levels of ABA that must be broken down before germination can occur.
• Seeds of tropical and subtropical fruits are sown during monsoon. The warm, moist conditions of the monsoon season provide ideal conditions for germination and seedling growth.
• In Walnut, Pecanut, Jackfruit, Ber-sowing of seeds in insitu is recommended. In situ sowing (sowing seeds directly at the permanent planting site) is recommended for these crops because their seedlings have a strong tap root that does not transplant well.
• Orthodox seeds: Seeds remain viable for long time at low temperature. These seeds can be dried to low moisture content and stored at cool temperatures without losing viability, making them easy to store and transport.
• Recalcitrant seed: Seeds don’t remain viable for long time at low temperature. So they should be sown immediately after extraction. Recalcitrant seeds are sensitive to desiccation and chilling injury — they lose viability rapidly when dried or cooled, so they must be planted fresh.
  • Example: 1. Mango 2. Citrus 3. Litchi 4. Loquat 5. Mangosteen 6. Avocado 7. Jack fruit 8. Rambutan 9. Barbados Cherry

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Methods to break dormancy

• Scarification: Process of breaking or softening the seed covering to make it permeable to water and gases. This method addresses physical dormancy caused by a hard seed coat.
  • Mechanically: Ber, Walnut, Peach — The seed coat is physically scratched, filed, or cracked to allow water penetration.
  • By Hot water: Guava, Strawberry — Seeds are soaked in hot water which softens the seed coat and makes it permeable.
  • By Acid: KNO₃ — Chemical treatment with concentrated sulphuric acid or other chemicals dissolves or weakens the seed coat.
• Stratification: Seeds are subjected to low temperature (Chilling temp) to break dormancy - Apple, Pear, Peach, Apricot. This method is also called moist chilling and involves placing seeds in moist sand or peat at temperatures of 2-7°C for several weeks. This simulates the natural winter conditions that temperate fruit seeds require before germination.
• Chemical treatment: Seeds are treated with 0.2% KNO₃ (Potassium nitrate). Potassium nitrate acts as a dormancy-breaking chemical by stimulating the production of gibberellins and other germination-promoting hormones.
• Use of hormones: 1. 100-500 ppm GA; 2. Etheral (500 ppm) 3. BA (10-20 ppm) (F) Cryopreservation: Storage in liquid N, at - 196 °C temperature or liquid CO2 at 43 °C temperature. Gibberellic acid (GA) is the most commonly used hormone for breaking dormancy, as it counteracts the effect of ABA. Cryopreservation is an advanced technique for long-term conservation of plant genetic material.
• Cryoprotactants: 1. Glycerol 2. DMSO (Dimethyl-sulphoxide). These chemicals protect cells from damage during the freezing and thawing process in cryopreservation by preventing ice crystal formation inside cells.

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Asexual Methods of Propagation

• It is also called ‘vegetative propagation’. The vegetative parts of a plant like leaf, stem, root or their modified forms are used for propagation. Since no sexual fusion is involved, the offspring are genetically identical to the parent plant (clones).
• Most of the horticultural crops are commercially propagated by vegetative or asexual method of propagation. This is because commercial growers need plants that are true-to-type, uniform, and come into bearing early.
• Most of the fruit crops are propagated by vegetative means.
• Types
  • Cutting
  • Layering
  • Grafting
  • Propagation by specialized organs

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✅ Merits of asexual propagation

• Many fruit and ornamental plants that do not produce seeds are multiplied by this method. Crops like banana, pineapple, strawberry, and fig that are seedless or produce non-viable seeds can only be multiplied vegetatively.
• Plants propagated by asexual propagation are true-to-type genetically. Since no genetic recombination occurs, every plant is a clone of the mother plant, ensuring uniformity in fruit quality, yield, and other characteristics.
• By top working (using budding and grafting), old and economically low productive fruit plants can be converted into superior ones. This is a cost-effective way to upgrade orchards without replanting.
• Advantages offered by rootstocks and scion can be exploited through asexual method. By grafting a desired variety onto the right rootstock, growers can achieve benefits like disease resistance, dwarfing, salt tolerance, and drought hardiness.
• Maturity is uniform and the plant gives quality yield. Vegetatively propagated plants flower and fruit at the same time, allowing for synchronized harvesting.
• Plants propagated by asexual method are small in size, so spraying of chemicals and harvesting are easy. The reduced tree size (especially when using dwarfing rootstocks) lowers management costs significantly.
• This method enables noble plant production, e.g., different colours of flowers in a single rose plant and different types of mangoes in one mango plant can be produced through asexual method only. This is achieved through multi-grafting, which is popular for exhibition and home garden purposes.

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❌ Demerits of asexual propagation

• By vegetative propagation, new varieties cannot be developed. Since there is no genetic recombination, asexual propagation only multiplies existing genotypes — it does not create new ones.
• It requires specialised skills, so it is an expensive method of propagation. Techniques like grafting and budding require trained personnel, and the success rate can vary with skill level and environmental conditions.
• The life span of asexually propagated plants is short as compared to sexually propagated ones. Seedling trees typically have a lifespan of 50-100+ years, while grafted trees may live for 30-50 years or less.
• These plants are more prone to biotic and abiotic stresses. The shallower root system of vegetatively propagated plants makes them more susceptible to drought, waterlogging, and wind damage compared to deep-rooted seedling trees.

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Tissue Culture (Micro propagation)

• It is a technique for growing plant tissues isolated from the parent plant in an artificial medium and controlled environment over a prolonged period under aseptic conditions. Tissue culture represents the most advanced form of vegetative propagation, allowing mass multiplication of plants in a laboratory setting.
• It is used on commercial scale in banana, gerbera, orchid, carnation, anthurium, etc. In banana, tissue culture has revolutionized the industry by enabling rapid production of millions of uniform, disease-free plantlets.
• It is based on the phenomenon of totipotency of a cell, which denotes the capacity of a plant cell to regenerate into a full-fledged plant having different organs. Totipotency means that every living plant cell contains the complete genetic information needed to develop into an entire organism.
• Callus is produced on explant in vitro due to wounding and growth substances, either endogenous or supplied exogenous in the medium. Callus is an undifferentiated mass of cells that can be induced to form shoots, roots, or embryos under appropriate hormonal stimulation.
• By using this technique, a large number of true-to-type virus-free saplings can be produced in a short span. This is one of the greatest advantages of tissue culture — the ability to produce disease-free planting material through meristem culture.
• Types
  • Callus culture
  • Cell culture
  • Meristem culture: Virus free plants are obtained. The meristematic tip (0.1-0.5 mm) of a shoot is too small to harbour viruses, so plants regenerated from it are virus-free. This is the primary method for producing virus-free stocks of crops like citrus, potato, and strawberry.
  • Organ culture
  • Protoplast culture
  • Shoot tip culture technique produce female plant in Banana. This is commercially important because female banana plants are more productive.
  • Micro Grafting: Citrus. Micro grafting involves grafting a tiny shoot tip onto a small seedling rootstock in vitro, combining the benefits of tissue culture (virus elimination) with grafting (rootstock advantages).
• Shoot tips and Micro-cuttings are highly suitable ex-plant for faster and disease free grape production.

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Plant propagation by specialised organs

• Specialised organs are modified stems or roots, developing above the ground surface or underground, which may be used for multiplication of plants. These organs serve as natural storage structures that allow plants to survive adverse conditions and regenerate.
• In horticulture, bulbous ornamentals include bulbs, corms, tubers, tuberous roots and rhizomes. Each of these structures has a distinct morphology and growth pattern.

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Bulb

• Bulb is a specialised underground structure having a flat basal stem and surrounded by fleshy scales. The fleshy scales are modified leaves that store food reserves (primarily carbohydrates) to support new growth.
• E.g., Onion. Other examples include tulip, lily, and garlic. Bulbs can be tunicate (covered by a dry papery outer scale, like onion) or non-tunicate (without a covering, like lily).

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Corm

• Corm is an underground modified solid or compressed stem oriented vertically in the side having nodes and buds. Unlike a bulb, a corm is a solid mass of stem tissue rather than layers of modified leaves. It stores food in the swollen stem itself.
• E.g. Gladiolus etc. Other examples include crocus and saffron. Corms produce small cormels at the base that can be separated and grown into new plants.

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Tuber

• It is an underground storage organ having special swollen modified stem or roots. Tubers develop when underground stems or roots swell with stored starch and other carbohydrates.
• E.g.
  • Root tuber like dahlia, caladium, dioscorea, Jerusalem artichoke, etc. and — Root tubers are formed from swollen roots and have buds only at the proximal end (crown).
  • Stem tuber like potato, begonia etc. — Stem tubers develop from swollen stolons (underground stems) and have eyes (buds) distributed over the surface.

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Rhizome

• A modified stem of some plant growing horizontally just below the ground surface. Rhizomes grow laterally through the soil, producing new shoots and roots at the nodes. They serve as both storage and propagation organs.
• E.g. ginger etc. Other examples include turmeric, banana (rhizome/corm), and canna.

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Runner

• It is a modified stalk, which is creeping in nature, produced in the leaf axil and grows out from the parent plant. Runners are above-ground horizontal stems that spread along the soil surface.
• It grows horizontally along the ground, where roots are produced at the nodes, which can be used to produce new plants. Each node can develop into an independent plant once it establishes its own root system.
• E.g., Strawberry (typical example) doob grass, chlorophytum, etc. Strawberry is the classic example of runner propagation — each mother plant can produce multiple runners, each giving rise to several new plants.

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Sucker

• It is a special shoot arising from the root or stem portion of a plant below the ground level. Suckers develop from adventitious buds on roots or from buds on the underground stem base.
• E.g., Banana, chrysanthemum (stem), Clerodendron splendens (root suckers), anthurium, etc. In banana, suckers are the primary means of propagation. Two types of suckers are used: sword suckers (with narrow, sword-shaped leaves — preferred) and water suckers (with broad leaves — less preferred).

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Offsets

• Date palm. An offset is a short, thick lateral shoot arising from the base of the mother plant. In date palm, offsets (also called suckers) are the primary method of propagation to maintain true-to-type varieties. Offsets weighing 10-15 kg and aged 3-5 years are preferred for planting.

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Commercial propagation methods of major fruit crops

Fruit Crop	Propagation Method
Citrus	Seed/Air layering
Grape	Hardwood cutting UPPSC 2021
Fig	Softwood cutting
Mango	Veneer grafting, Inarching, Softwood grafting
Pomegranate	Hardwood Cutting/Air layering
Litchi	Air layering/Gootee
Guava	Stooling/Mound layering
Sapota, Jackfruit, Loquat	Inarching FCI, NABARD 2021
Banana	Sword sucker/Tissue Culture UPPSC 2021
Date palm	Offshoot/sucker
Pineapple	Suckers/slips
Strawberry	Runners UPPSC 2021
Aonla	Patch budding
Ber	Ring & T-budding
Custard apple	T-budding
Rose	Shield budding
Apple	Shield budding, Tongue Grafting RRB-SO-19
Papaya, Phalsa, Coffee, Jamun, Coconut, Arecanut, Acid lime, Passion Fruit	Seeds

Knowing the commercial propagation method for each fruit crop is essential for competitive exams. Key facts to remember: Mango — veneer/stone grafting; Citrus — T-budding; Guava — air layering/stooling; Grape — hardwood cuttings; Banana — suckers/tissue culture; Apple — tongue grafting; Papaya — seeds.

Summary Cheat Sheet

Concept / Topic	Key Details
Sexual propagation	By seeds; gives genetic variation; used for rootstocks
Asexual / Vegetative	From plant parts; genetically identical (true-to-type)
Cutting	Stem/root piece planted for rooting; grapes, fig, pomegranate
Layering	Rooting while attached to parent plant
Air layering (gootee)	Bark ringed + moist moss wrapped; guava, litchi
Ground layering	Branch bent to soil; jasmine
Mound / Stool layering	Soil mounded around shoots; apple rootstocks
Budding	Single bud transferred to rootstock
T-budding	Most common budding; citrus, rose
Shield budding	Variation of T-budding
Patch budding	For thick-barked species; walnut, mango
Grafting	Scion (desired variety) joined to rootstock
Tongue / Whip grafting	Small diameter stocks; apple, pear
Veneer grafting	Most common for mango
Softwood grafting	Green wood grafting; cashew, mango
Inarching (approach)	Both scion and stock on own roots until union; mango, sapota
Tissue culture	Mass propagation; banana, orchid, date palm