Plant Biotechnology and Micropropagation

Micropropagation

• Micropropagation is a method of producing plants from small plant parts, tissue, or cells under aseptic conditions, based on the principle of totipotency.
• Strawberry was the first fruit crop to be commercially propagated using micropropagation technique.

Advantages of Micropropagation

• Large-scale multiplication of virus-free planting materials in limited time and space.
• Year-round production possible.
• Beneficial for plants where vegetative propagation is not easy, such as papaya.
• Production of secondary metabolites.
• Helps in long-term storage in lesser space.

Methods of Micropropagation

• Meristem tip culture: eliminates virus from infected plants, consists of 1 or 2 pairs of leaf primordia.
• Callus culture: unorganised mass of parenchymatous cells, undergoes organogenesis in two steps.
• Anther culture: produces homozygous plants, first reported in Datura by Guha and Maheshawari (1959).
• Cell suspension culture: involves homogenizing a piece of callus into liquid medium and shaking until medium becomes cloudy with suspended cells.
• Ovule culture: unfertilized or just fertilized ovule excised and cultured.

Root Cuttings

• Used for plants that produce suckers freely, such as blackberry and raspberry.
• Preparation of root cuttings involves cutting roots into pieces, 1 cm thick and 10-15 cm long, in late winter or early spring.
• Correct polarity is important, with the proximal end having a straight cut and the distal end having a slanting cut.

Budding

• Involves attaching a scion with only one bud to a stock.
• Scion is prepared by trimming the base to a wedge shape, exactly the same size and shape as the V-wedge on the stock.
• Waxing is essential to prevent drying out of the cut surfaces.

Grafting

• Detached scion grafting: also known as side graftage, useful for trees that are too large for whip or tongue grafting but not large enough for cleft or wedge grafting.
• Side-stub grafting: involves making an oblique cut into the rootstock at an angle of about 20-30°, with a scion that is about 7.5 cm long and relatively thin.