👨‍❤️‍💋‍👨 Method of Propagation

👉🏻 Plants can be propagated by sexual and asexual means.

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.
• 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.

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).
• It is an easy, simple and convenient method of plant propagation.
• Some plants like papaya, marigold, chilli, capsicum, tomato, etc., cannot be propagated by asexual method.
• It is the only means of creating genetic diversity of plants.
• New varieties and cultivars of ornamental and vegetable crops can be developed only by this method.
• A large number of rootstocks for budding and grafting purpose is also raised by this method.
• Seeds can be transported easily and stored for a longer time using this method.

Demerits of sexual propagation

• Sexually propagated plants show variations and are not genetically true-to-type to the mother plants.
• Plants that are propagated through seeds have long gestation period, which results in delayed flowering and fruiting.
• Plants grow vigorously and cause obstruction in intercultural practices like harvesting and spraying.
• Advantages offered by rootstocks and scion as in asexual propagation cannot be exploited through sexual method.
• Crop species, which do not produce seeds like pineapple, banana, strawberry, fig, jasmine, hibiscus, bougainvillea, etc., cannot multiply by this method.

Seed

• Seed quality is considered best if pure seed % is above 98%. Moisture content: 6-8% Germination %: 60-70%.

Dormancy

• Inability of viable seed to germinate.
• Hard seed coat dormancy: Ber, Guava, Walnut
• Dormancy due to presence of ABA — temperate fruits
• Seeds of tropical and subtropical fruits are sown during monsoon.
• In Walnut, Pecanut, Jackfruit, Ber-sowing of seeds in insitu is recommended.
• Orthodox seeds: Seeds remain viable for long time at low temperature.
• Recalcitrant seed: Seeds don’t remain viable for long time at low temperature. So they should be sown immediately after extraction.
  • Example: 1. Mango 2. Citrus 3. Litchi 4. Loquat 5. Mangosteen 6. Avocado 7. Jack fruit 8. Rambutan 9. Barbados Cherry

Methods to break dormancy

• Scarification: Process of breaking or softening the seed covering to make it permeable to water and gases.
  • Mechanically: Ber, Walnut, Peach
  • By Hot water: Guava, Strawberry
  • By Acid: KNO₃
• Stratification: Seeds are subjected to low temperature (Chilling temp) to break dormancy - Apple, Pear, Peach, Apricot
• Chemical treatment: Seeds are treated with 0.2% KNO₃ (Potassium nitrate)
• 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.
• Cryoprotactants: 1. Glycerol 2. DMSO (Dimethyl-sulphoxide)

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.
• Most of the horticultural crops are commercially propagated by vegetative or asexual method of propagation.
• Most of the fruit crops are propagated by vegetative means.
• Types
  • Cutting
  • Layering
  • Grafting
  • Propagation by specialized organs

✅ Merits of asexual propagation

• Many fruit and ornamental plants that do not produce seeds are multiplied by this method.
• Plants propagated by asexual propagation are true-to-type genetically.
• By top working (using budding and grafting), old and economically low productive fruit plants can be converted into superior ones.
• Advantages offered by rootstocks and scion can be exploited through asexual method.
• Maturity is uniform and the plant gives quality yield.
• Plants propagated by asexual method are small in size, so spraying of chemicals and harvesting are easy.
• 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.

❌ Demerits of asexual propagation

• By vegetative propagation, new varieties cannot be developed.
• It requires specialised skills, so it is an expensive method of propagation.
• The life span of asexually propagated plants is short as compared to sexually propagated ones.
• These plants are more prone to biotic and abiotic stresses.

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.
• It is used on commercial scale in banana, gerbera, orchid, carnation, anthurium, etc.
• 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.
• Callus is produced on explant in vitro due to wounding and growth substances, either endogenous or supplied exogenous in the medium.
• By using this technique, a large number of true-to-type virus-free saplings can be produced in a short span.
• Types
  • Callus culture
  • Cell culture
  • Meristem culture: Virus free plants are obtained
  • Organ culture
  • Protoplast culture
  • Shoot tip culture technique produce female plant in Banana.
  • Micro Grafting: Citrus
• Shoot tips and Micro-cuttings are highly suitable ex-plant for faster and disease free grape production.

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.
• In horticulture, bulbous ornamentals include bulbs, corms, tubers, tuberous roots and rhizomes.

Bulb

• Bulb is a specialised underground structure having a flat basal stem and surrounded by fleshy scales.
• E.g., Onion.

Corm

• Corm is an underground modified solid or compressed stem oriented vertically in the side having nodes and buds.
• E.g. Gladiolus etc.

Tuber

• It is an underground storage organ having special swollen modified stem or roots.
• E.g.
  • Root tuber like dahlia, caladium, dioscorea, Jerusalem artichoke, etc. and
  • Stem tuber like potato, begonia etc.

Rhizome

• A modified stem of some plant growing horizontally just below the ground surface
• E.g. ginger etc.

Runner

• It is a modified stalk, which is creeping in nature, produced in the leaf axil and grows out from the parent plant.
• It grows horizontally along the ground, where roots are produced at the nodes, which can be used to produce new plants.
• E.g., Strawberry (typical example) doob grass, chlorophytum, etc.

Sucker

• It is a special shoot arising from the root or stem portion of a plant below the ground level.
• E.g., Banana, chrysanthemum (stem), Clerodendron splendens (root suckers), anthurium, etc.

Offsets

• Date palm

Commercial propagation methods of major fruit crops