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Artificial cloning in plants ...

Principles continued ...

Yes, we have no banana's ...

  • Banana's are one of the oldest crops and first to be cloned.
  • A wild banana is full of hard seeds and is inedible.
  • A mutation made them parthanocarpic which means they produce fruit without fertile seeds. It made them good to eat and they were sterile.
  • The fungal panama disease/Black sigatoka.
  • New biotechnologies e.g. genetic engineering/ micropropagation.
  • Genetically engineered strains of banana's with resistance genes from the original wild fruit could be microporagated and used to restock banana plaintains acroos the region.

ARGUMENTS AGAINST PROPAGATION:-

  • It produces a monoculture- many plants which are genetically identical- so they are susceptible to the same diseases or changes in growing conditions.
  • It is relatively expensive process and requires skilled workers.
  • The explants and plantlets are vulnerable to infection by moulds and other diseases during the production process.
  • If the source material is infected with a virus all of the clones will be infected
  • In some instances large numbers of new plants are lost during the process.

Adavantages and disadvantages of propagation ...

The number of plants being grown by propagation is constantly increasing. These include potatoes,sugar cane, bananas,cassava,grapes,strawberries,douglas firs,orchids and crysanthemums.

ARGUMENTS FOR PROPAGATION:-

  • Micropropagation allows for rapid production of large number of plants with known genetic makeup which will yield good crops.
  • culturing meristem tissue produces disease free plants.
  • It makes it possible to produce viable numbers of plants after the gentic modification of plants after the genetic modification of plant cells.
  • It enables large numbers of new plants which are seedless and therefore sterile to meet consumer tastes e.g. bananas and grapes.
  • It provides a way of growing plants which are generally infertile or difficult to grow using seeds e.g. orchid.
  • It allows the increase of the numbers of rare or endangered plants-This is obtained reliably.
  • The explant is placed in a sterile culture medium which contains a balance of plant hormones e.g. auxin and cytokins. which stimulate mitosis. The cells profilerate forming a mass of identical cells known as a callus.
  • The callus is divided up and individual cells or clumps from the callus are transferred to a new culture medium which contain a mixture of hormones and nutrients which stimulates the development of tiny genetically identical plantlets.
  • The plantelets are potted into compost where they grow into small plants.
  • The young plants are planted to grow and produce a crop
  • The scale of propagation is increasing. It now takes place in bioreactors which effectively make artificial embryo plants to be packaged in artificial seeds.

Basic principles of micropropagation and tissue culture :-

Ways in which plants can be propagated:-

  • A small sample is taken of a tissue form the plant you intend to clone the meristem tissue from the shoot tips and the axial buds are often dissected in sterile conditions to contamination by fungi and bacteria. the tissue is known to be virus-free.
  • The sample is sterilised by using sterilising agent such as bleach,ethanol or sodium dichloroisocyanurate. The latter does not need to be rinsed off which means that the tissue is still sterile. The material removed from a plant is a explant.

One protocol is used and present in the Royal Botanical Garden at Kew and uses sodium dichloroisocyanurate which are sterlising tablets use to make drinking water and babies bottles' safe.

This keeps the plant sterile without having to be placed in a sterile lab.This makes it useful for scientists in the field working with the rare and endangered plant material and for use in schools.

Other protocols are suited to industrial propagation where large sterlising units are available.

This method is used to produce plants when a desirable plant:-

  • Does not readily produce seeds
  • Doesn't respond well to natural cloning
  • Has been genetically modified or selectively bred with difficulty
  • Is required to be pathogen free by growers e.g. strawberries,banana's and potatoes.

Micropropagation using tissue culture ...

Micropropagation involves the process of making large numbers of genetically identical offspring from a single parent using tissue culture techniques.

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