Biotechnological Applications in Agriculture
Biotechnological applications in agriculture aim to raise food production while cutting the use of chemicals. This page covers the three research areas of biotechnology, plant tissue culture (totipotency, micropropagation, somaclones, virus-free meristems and somatic hybrids), genetically modified crops, Bt cotton with its cry genes, and RNA interference against nematodes, as in the NCERT Class 12 chapter Biotechnology and its Applications. NEET often asks how Bt toxin acts, which cry gene controls which pest, and the steps of RNAi in questions on biotechnological applications in agriculture.
- ★ Must learn Biotechnology: industrial-scale production of biopharmaceuticals and biologicals using genetically modified microbes, fungi, plants and animals.
- Three critical research areas: the best catalyst, optimal conditions for it, and downstream processing to purify the product.
- ★ Must learn Totipotency: the capacity to generate a whole plant from any cell or explant.
- Micropropagation gives thousands of plants in a short time; all are somaclones (genetically identical to the parent).
- Apical and axillary meristems stay free of virus, so they give virus-free plants (banana, sugarcane, potato).
- Somatic hybridisation fuses protoplasts of two varieties; tomato and potato gave the pomato.
- ★ Must learn GMO: an organism whose genes have been altered by manipulation; golden rice is Vitamin A enriched rice.
- ★ Must learn Bt toxin is an inactive protoxin; the alkaline pH of the insect gut activates it, and it makes pores in midgut epithelial cells.
- ★ Must learn cryIAc and cryIIAb control cotton bollworms; cryIAb controls the corn borer.
- ★ Must learn RNAi: a complementary dsRNA silences a specific mRNA; it protects tobacco roots from Meloidogyne incognita.
1. Biotechnology and Its Applications
- ★ Exam imp Biotechnology deals mainly with the industrial-scale production of biopharmaceuticals and biologicals.
- It uses genetically modified microbes, fungi, plants and animals for this production.
- Biotechnology has given humans many useful products by using microbes, plants and animals and their metabolic machinery.
- Recombinant DNA technology can engineer microbes, plants and animals so that they gain novel capabilities.
1.1 Areas where biotechnology is applied
| Field | Applications |
|---|---|
| Health | Therapeutics; diagnostics |
| Food | Genetically modified crops for agriculture; processed food |
| Environment and energy | Bioremediation; waste treatment; energy production |
Remember the seven applications as 2 + 2 + 3: two for health (therapeutics, diagnostics), two for food (GM crops, processed food) and three for environment and energy (bioremediation, waste treatment, energy production).
1.2 Three critical research areas
- The best catalyst: an improved organism, usually a microbe, or a pure enzyme.
- Optimal conditions: created through engineering, so that the catalyst can act.
- Downstream processing: technologies that purify the protein or organic compound.
The three Cs of biotechnology research: Catalyst, Conditions and Clean-up (downstream purification).
Biotechnology has improved the quality of human life especially through food production and health. This page covers food production; medicine has its own page.
2. Three Options for Increasing Food Production
- Agro-chemical based agriculture
- Organic agriculture
- Genetically engineered crop-based agriculture
2.1 Limits of the Green Revolution
- ★ Exam imp The Green Revolution tripled the food supply, yet this was not enough to feed the growing human population.
- Yields rose partly because of improved crop varieties.
- ★ Exam imp Yields rose mainly because of better management practices and agrochemicals (fertilisers and pesticides).
- For farmers in the developing world, agrochemicals are often too expensive.
- Yields of existing varieties cannot be raised further by conventional breeding.
3. Plant Tissue Culture
3.1 Why tissue culture developed
- Traditional breeding could not keep pace with the demand for food.
- It also failed to give a fast and efficient system for crop improvement.
- So another technology, tissue culture, was developed.
3.2 Explant and totipotency
- In the 1950s, scientists learnt that whole plants could be regenerated from explants.
- ★ Exam imp Explant: any part of a plant taken out and grown in a test tube, under sterile conditions, in special nutrient media.
★ Very important Totipotency: the capacity to generate a whole plant from any cell or explant.
3.3 The nutrient medium
- ★ Exam imp A carbon source such as sucrose.
- Inorganic salts.
- Vitamins.
- Amino acids.
- Growth regulators such as auxins and cytokinins.
The medium in order: Some Salty Vegetables Are Rich: Sucrose, inorganic Salts, Vitamins, Amino acids, growth Regulators (auxins, cytokinins).
3.4 Micropropagation and somaclones
- Tissue culture can propagate a large number of plants in very short durations.
- ★ Exam imp Micropropagation: producing thousands of plants through tissue culture.
- ★ Exam imp Somaclones: plants from micropropagation; each is genetically identical to the original plant.
- Tomato, banana and apple have been produced on a commercial scale by this method.
3.5 Virus-free plants from meristems
Tissue culture can also recover healthy plants from diseased plants:
- The plant is infected with a virus.
- Its meristem (apical and axillary) is still free of virus.
- The meristem is removed and grown in vitro.
- The result is a virus-free plant.
- Meristems of banana, sugarcane and potato have been cultured successfully.
Thousands of identical plants (somaclones) at a commercial scale.
Examples: tomato, banana, apple.
Virus-free plants from an infected plant, because the meristem has no virus.
Examples: banana, sugarcane, potato.
Micropropagation is T-B-A (Tomato, Banana, Apple); meristem culture is B-S-P (Banana, Sugarcane, Potato). Banana is the only crop in both lists.
4. Somatic Hybridisation
- Single cells are isolated from plants.
- Their cell walls are digested, giving naked protoplasts, each surrounded only by a plasma membrane.
- Protoplasts from two different varieties, each with a desirable character, are fused.
- The fusion gives hybrid protoplasts.
- Each hybrid protoplast is grown into a new plant.
★ Very important The new plants are somatic hybrids, and the process is called somatic hybridisation.
- ★ Exam imp Pomato: formed by fusing a protoplast of tomato with one of potato, combining their characters.
- The pomato did not have all the desired characters, so it was not used commercially.
- Tissue culture and somatic hybridisation offer vast potential for manipulating plants in vitro to produce new varieties.
Extra Depth: Cell walls are usually removed with wall-digesting enzymes such as cellulase and pectinase.
Pomato = Potato + Tomato: the name itself tells the two parents.
What is an explant?
Name the growth regulators added to the culture medium.
Why are micropropagated plants called somaclones?
Which part of an infected plant gives virus-free plants?
What is a naked protoplast?
5. Genetically Modified Crops
- Farmers need maximum yield with less fertiliser and fewer chemicals, to reduce harm to the environment.
- The use of genetically modified crops is a possible solution.
★ Very important Genetically Modified Organisms (GMO): plants, bacteria, fungi and animals whose genes have been altered by manipulation.
- GMOs are made by methods other than natural ones, which transfer one or more genes from one organism to another.
- The method used is generally recombinant DNA technology.
5.1 How genetic modification has helped
| Benefit | Detail |
|---|---|
| Tolerance to abiotic stresses | Crops tolerate cold, drought, salt and heat better |
| Less reliance on chemical pesticides | Pest-resistant crops |
| Fewer post-harvest losses | Less of the harvest is lost after harvesting |
| Better mineral use | Plants use minerals more efficiently; this prevents early exhaustion of soil fertility |
| Higher nutritional value | Golden rice: Vitamin A enriched rice |
The five benefits in order: Some Plants Prefer More Nutrients: Stress tolerance, Pesticides reduced, Post-harvest losses reduced, Mineral use, Nutritional value.
- GM has also made tailor-made plants that supply industries with starches, fuels and pharmaceuticals.
- Pest-resistant plants can decrease the amount of pesticide used.
- GM plants raise crop yields, reduce post-harvest losses, tolerate stresses and improve the nutritional value of food.
6. Bt Cotton: Pest-Resistant Plants
6.1 Bt toxin as a bio-pesticide
- Bt toxin is produced by the bacterium Bacillus thuringiensis (Bt for short).
- ★ Exam imp The Bt toxin gene has been cloned from the bacterium and expressed in plants.
- Such plants resist insects without insecticides; in effect, a bio-pesticide has been created.
- ★ Exam imp Examples: Bt cotton, Bt corn, rice, tomato, potato and soyabean.
Bt crops: Clever Cooks Roast Tomatoes, Potatoes and Soya: Cotton, Corn, Rice, Tomato, Potato, Soyabean.
6.2 Insects killed by Bt proteins
- Some strains of Bacillus thuringiensis produce proteins that kill certain insects:
| Insect group | Examples |
|---|---|
| Lepidopterans | Tobacco budworm, armyworm |
| Coleopterans | Beetles |
| Dipterans | Flies, mosquitoes |
Bt proteins target an LCD: Lepidopterans, Coleopterans and Dipterans.
6.3 How Bt toxin kills an insect
- B. thuringiensis forms protein crystals during a particular phase of its growth.
- These crystals contain a toxic insecticidal protein.
- In the bacterium, the toxin exists as an inactive protoxin, so it does not kill the Bacillus.
- An insect ingests the inactive toxin.
- The alkaline pH of the insect gut solubilises the crystals and converts the protoxin into the active toxin.
- The activated toxin binds to the surface of midgut epithelial cells and creates pores.
- The cells swell and lyse, and the insect eventually dies.
Read the action as C-A-B-P-L: Crystal eaten, Alkaline activation, Binding to midgut cells, Pores, Lysis.
6.4 The cry genes
- Specific Bt toxin genes were isolated from B. thuringiensis and incorporated into several crop plants such as cotton.
- The choice of gene depends on the crop and the targeted pest.
- ★ Exam imp Most Bt toxins are insect-group specific.
- The toxin is coded by genes named cry; there are many of them.
| Gene | Pest controlled by its protein |
|---|---|
| cryIAc | Cotton bollworms |
| cryIIAb | Cotton bollworms |
| cryIAb | Corn borer |
cryIAc: c for cotton; cryIAb: b for borer; cryIIAb, the only double-I gene, is the second cotton gene.
Write the gene in italics with a small c (cry) and the protein it codes with a capital C (Cry protein). Check the Roman numeral first (I or II), then the last letters (Ac or Ab); options often swap these.
- The gut pH that activates Bt toxin is alkaline, not acidic.
- The toxin binds to midgut epithelial cells, makes pores and causes swelling and lysis.
- cryIAb controls the corn borer; cryIAc and cryIIAb control cotton bollworms.
- The bacterium is safe because its toxin is an inactive protoxin, not because it is resistant or the toxin is held in a sac.
7. Nematode Resistance through RNA Interference
7.1 The problem
- Several nematodes parasitise a wide variety of plants and animals, including human beings.
- ★ Exam imp The nematode Meloidogyne incognita infects the roots of tobacco plants.
- This infection causes a great reduction in yield.
- A novel strategy based on RNA interference (RNAi) was adopted to prevent it.
7.2 What RNA interference is
★ Very important RNA interference (RNAi): silencing of a specific mRNA by a complementary double-stranded RNA (dsRNA), which binds to the mRNA and prevents its translation.
- ★ Exam imp RNAi takes place in all eukaryotic organisms as a method of cellular defence.
- The complementary RNA may come from an infection by viruses with RNA genomes.
- It may also come from mobile genetic elements (transposons) that replicate via an RNA intermediate.
7.3 Making a nematode-resistant plant
- Nematode-specific genes were introduced into the host plant using Agrobacterium vectors.
- The introduced DNA produced both sense and anti-sense RNA in the host cells.
- Being complementary, the two RNAs formed a double-stranded RNA (dsRNA).
- The dsRNA initiated RNAi and silenced the specific mRNA of the nematode.
- The parasite could not survive in a transgenic host expressing the specific interfering RNA.
- The transgenic plant was thus protected from the parasite.
The RNAi steps: All Sense Doubles into Silence: Agrobacterium, Sense and anti-sense RNA, Double-stranded RNA, Silencing of nematode mRNA.
Extra Depth: Meloidogyne is known as the root-knot nematode, because infected roots form knot-like swellings (galls), as in panel (a).
Three checks for any RNAi statement: the dsRNA is made by the host plant; it silences the nematode's mRNA, not the plant's own genes; and it blocks translation, not replication of DNA.
Name the bacterium that produces Bt toxin.
What activates the Bt protoxin in the insect?
Which gene's protein controls the corn borer?
Which nematode infects tobacco roots?
How is dsRNA formed in the transgenic tobacco plant?
8. Exam Essentials
Pairs to Match
| List I | List II |
|---|---|
| Totipotency | Capacity of any cell or explant to form a whole plant |
| Explant | Plant part grown in a test tube under sterile conditions |
| Somaclones | Genetically identical plants from micropropagation |
| Apical and axillary meristem | Virus-free tissue used to raise virus-free plants |
| Pomato | Somatic hybrid of tomato and potato |
| Golden rice | Vitamin A enriched rice |
| Bacillus thuringiensis | Source of Bt toxin |
| Alkaline pH of insect gut | Activates the Bt protoxin |
| Midgut epithelial cells | Binding site of the active Bt toxin |
| cryIAc and cryIIAb | Cotton bollworms |
| cryIAb | Corn borer |
| Meloidogyne incognita | Infects roots of tobacco |
| Agrobacterium | Vector for nematode-specific genes |
| dsRNA | Silences a specific mRNA (RNAi) |
| Transposons replicating via an RNA intermediate | Source of complementary RNA for RNAi |
- Bt toxin does not kill Bacillus thuringiensis itself, because it is stored as an inactive protoxin.
- Most Bt toxins are insect-group specific, not general poisons.
- The meristem stays free of virus even when the rest of the plant is infected.
- The pomato did not have all the desired characters, so it is not used commercially.
- Green Revolution gains came only partly from improved varieties.
- Somaclones show no genetic variation; they are identical to the parent plant.
- RNAi occurs in all eukaryotes, not only in plants.
Numbers to Remember
- Green Revolution: food supply tripled.
- Whole plants first regenerated from explants: 1950s.
- Critical research areas of biotechnology: 3; options for raising food production: 3.
- Benefits of GM plants listed: 5.
- Micropropagation: thousands of plants in a very short time.
- Transgenic tobacco roots were examined 5 days after deliberate nematode infection.
Examples to Remember
| Type | Examples |
|---|---|
| Micropropagated on a commercial scale | Tomato, banana, apple |
| Virus-free meristem culture | Banana, sugarcane, potato |
| Somatic hybrid | Pomato (tomato + potato) |
| Bt crops | Cotton, corn, rice, tomato, potato, soyabean |
| Lepidopterans killed by Bt | Tobacco budworm, armyworm |
| Coleopterans and dipterans killed by Bt | Beetles; flies, mosquitoes |
| Abiotic stresses tolerated by GM crops | Cold, drought, salt, heat |
| Products of tailor-made plants | Starches, fuels, pharmaceuticals |
| Growth regulators in the medium | Auxins, cytokinins |
| Sources of complementary RNA | RNA viruses; transposons replicating via RNA |
- Totipotency, micropropagation and somaclones are a common statement set.
- Sequence questions use the Bt toxin action and the RNAi steps; learn both orders.
- Traps: "acidic gut", "Bt toxin kills the bacterium", "RNAi silences DNA" and "cryIAb controls bollworms" are all false.
9. Quick Revision
- Biotechnology: industrial-scale production of biopharmaceuticals and biologicals with GM microbes, fungi, plants and animals.
- Research areas: best catalyst, optimal conditions, downstream processing.
- Food options: agro-chemical, organic and GE crop-based agriculture.
- Green Revolution tripled food supply, mainly through management and agrochemicals.
- Explant: plant part grown in a test tube in sterile nutrient media (1950s discovery).
- Totipotency: whole plant from any cell or explant.
- Medium: sucrose, inorganic salts, vitamins, amino acids, auxins and cytokinins.
- Micropropagation gives somaclones; tomato, banana and apple are produced commercially.
- Virus-free plants come from apical and axillary meristems (banana, sugarcane, potato).
- Fused protoplasts give somatic hybrids; the pomato was not used commercially.
- Tissue culture and somatic hybridisation can produce new plant varieties in vitro.
- GMO: genes altered by manipulation; golden rice is Vitamin A enriched.
- Bt protoxin turns active in the alkaline insect gut and lyses midgut epithelial cells.
- cryIAc, cryIIAb: cotton bollworms; cryIAb: corn borer.
- RNAi: host-made dsRNA silences nematode mRNA; Agrobacterium delivers the genes.
10. Solved Examples
List I: A. cryIAb, B. cryIAc, C. Meloidogyne incognita, D. Golden rice
List II: I. Cotton bollworm, II. Vitamin A, III. Corn borer, IV. Tobacco roots
Choose the correct answer:
(A) A-I, B-III, C-IV, D-II
(B) A-III, B-I, C-IV, D-II
(C) A-III, B-I, C-II, D-IV
(D) A-IV, B-I, C-III, D-II
Answer: (B). cryIAb controls the corn borer (III), cryIAc controls cotton bollworms (I), Meloidogyne incognita infects tobacco roots (IV) and golden rice is Vitamin A enriched (II).
A. It is produced by Bacillus thuringiensis as protein crystals.
B. Inside the bacterium it exists as an active toxin.
C. The acidic pH of the insect gut activates it.
D. The active toxin creates pores in midgut epithelial cells.
E. Most Bt toxins are insect-group specific.
Choose the correct answer:
(A) A, B and C only
(B) A, D and E only
(C) B, C and D only
(D) C, D and E only
Answer: (B). B is wrong: the toxin is an inactive protoxin inside the bacterium. C is wrong: the gut pH is alkaline. A, D and E are correct.
A. Cells swell and lyse.
B. The insect ingests the protoxin crystals.
C. The toxin binds to midgut epithelial cells and creates pores.
D. Alkaline pH solubilises the crystals and activates the toxin.
Choose the correct answer:
(A) B, D, C, A
(B) B, C, D, A
(C) D, B, C, A
(D) B, D, A, C
Answer: (A). The insect first eats the crystals (B); the alkaline gut activates the toxin (D); the toxin binds and makes pores (C); the cells swell and lyse (A).
(A) Mature leaf
(B) Apical and axillary meristem
(C) Phloem tissue
(D) Root hair
Answer: (B). The apical and axillary meristem is free of virus even in an infected plant, so it is removed and grown in vitro.
(A) It silences a specific mRNA of the nematode.
(B) The dsRNA forms from sense and anti-sense RNA.
(C) The genes were introduced using Agrobacterium vectors.
(D) RNAi occurs only in prokaryotes.
Answer: (D). RNAi takes place in all eukaryotic organisms as a method of cellular defence; statements A, B and C are correct.
Statement II: Each micropropagated plant is genetically identical to the original plant.
Choose the correct answer:
(A) Both Statement I and Statement II are correct
(B) Both Statement I and Statement II are incorrect
(C) Statement I is correct but Statement II is incorrect
(D) Statement I is incorrect but Statement II is correct
Answer: (A). Somaclones are genetically identical copies of the parent plant, so both statements are correct.
11. Practice Questions
- Match List I (insect group) with List II (example).
A. Lepidopterans, B. Coleopterans, C. Dipterans
I. Beetles, II. Mosquitoes, III. Armyworm
(A) A-III, B-I, C-II
(B) A-I, B-III, C-II
(C) A-II, B-I, C-III
(D) A-III, B-II, C-IAnswer: (A). Armyworm is a lepidopteran, beetles are coleopterans and mosquitoes are dipterans. - Read the statements on tissue culture.
A. Totipotency is the capacity to form a whole plant from any cell or explant.
B. The medium needs sucrose as a carbon source.
C. Growth regulators are not needed in the medium.
D. Explants are grown under sterile conditions.
(A) A, B and D only
(B) A and C only
(C) B, C and D only
(D) A, B, C and DAnswer: (A). C is wrong: auxins and cytokinins are added to the medium. - Arrange the steps of somatic hybridisation in order.
A. Fusion of protoplasts
B. Digestion of cell walls
C. Growth into a new plant
D. Isolation of single cells
(A) D, B, A, C
(B) B, D, A, C
(C) D, A, B, C
(D) A, B, D, CAnswer: (A). Cells are isolated, walls digested, protoplasts fused, and the hybrid grown. - Statement I: The Green Revolution tripled the food supply.
Statement II: Its increase in yield was mainly due to improved crop varieties.
(A) Both correct
(B) Both incorrect
(C) I correct, II incorrect
(D) I incorrect, II correctAnswer: (C). The gain came mainly from management practices and agrochemicals. - Which is NOT a benefit of GM plants?
(A) Tolerance to drought
(B) Reduced post-harvest losses
(C) Greater reliance on chemical pesticides
(D) Golden rice with Vitamin AAnswer: (C). GM crops reduce reliance on chemical pesticides. - The complementary RNA for RNAi may come from
(A) RNA viruses only
(B) transposons only
(C) RNA viruses and transposons
(D) ribosomesAnswer: (C). Viruses with RNA genomes and transposons that replicate via an RNA intermediate. - Match List I with List II.
A. Pomato, B. Somaclone, C. Explant, D. Meristem
I. Virus-free tissue, II. Somatic hybrid, III. Plant part grown in vitro, IV. Identical plant from micropropagation
(A) A-II, B-IV, C-III, D-I
(B) A-IV, B-II, C-III, D-I
(C) A-II, B-III, C-IV, D-I
(D) A-I, B-IV, C-III, D-IIAnswer: (A). Pomato is a somatic hybrid; a somaclone is an identical micropropagated plant.
- Which part of the plant is best suited for making virus-free plants, and why?Answer: The apical and axillary meristem; it remains free of virus even when the plant is infected.
- What is the major advantage of producing plants by micropropagation?Answer: A large number of genetically identical plants (somaclones) is obtained in a very short time.
- Name the components of the medium used to propagate an explant in vitro.Answer: A carbon source (sucrose), inorganic salts, vitamins, amino acids and growth regulators such as auxins and cytokinins.
- Crystals of Bt toxin do not kill the bacteria that make them because:
(a) the bacteria are resistant
(b) the toxin is immature
(c) the toxin is inactive
(d) the bacteria enclose the toxin in a special sacAnswer: (c). The toxin exists as an inactive protoxin and is activated only in the alkaline insect gut. - Compare the advantages and disadvantages of producing GM crops.Answer: Advantages: stress tolerance, less pesticide use, fewer post-harvest losses, better mineral use, higher nutrition. Disadvantages: unpredictable effects in the ecosystem, and ethical and patent concerns.
- What are Cry proteins? Name an organism that produces them and how humans use them.Answer: Insecticidal proteins coded by cry genes of Bacillus thuringiensis; their genes are put into crops such as cotton to make pest-resistant Bt crops.
- Suggest a way to remove oil from seeds using rDNA technology.Answer: Oil is made from fatty acids and glycerol; silence or remove the genes for the enzymes that make them (for example, by RNAi), so the seeds store little oil.
- What is golden rice?Answer: A genetically modified, Vitamin A enriched rice; its grains carry -carotene, the source of Vitamin A, which gives them a yellow colour.
Common Mistakes to Avoid
- Correct: the Bt protoxin is activated by the alkaline pH of the insect gut, not an acidic pH.
- Correct: the active Bt toxin acts on midgut epithelial cells, not on nerve cells.
- Correct: cryIAb controls the corn borer; cryIAc and cryIIAb control cotton bollworms.
- Correct: RNAi silences a specific mRNA and stops its translation; it does not destroy the nematode's DNA.
- Correct: Meloidogyne incognita infects the roots of tobacco, not cotton.
- Correct: somaclones are genetically identical; somatic hybrids combine two varieties.
- Correct: the meristem used for virus-free plants is apical and axillary, and it is virus-free even in an infected plant.
- Correct: Green Revolution yields came mainly from management and agrochemicals, only partly from varieties.
Frequently Asked Questions
What are the main biotechnological applications in agriculture?
Biotechnology raises food production through tissue culture, which gives micropropagated and virus-free plants and somatic hybrids, and through genetically modified crops. Important GM examples are pest-resistant Bt cotton and tobacco protected from nematodes by RNA interference. GM crops also tolerate stress, reduce losses and improve nutrition.
Why does Bt toxin not kill Bacillus thuringiensis?
In the bacterium, Bt toxin exists as an inactive protoxin inside protein crystals. Only when an insect eats the crystals does the alkaline pH of its gut solubilise them and convert the protoxin into the active toxin. The active form then attacks the insect's midgut epithelial cells.
How does Bt toxin kill an insect?
The activated toxin binds to the surface of the midgut epithelial cells and creates pores in them. The cells swell and lyse, and the insect eventually dies. Because most Bt toxins are insect-group specific, the choice of gene depends on the crop and the pest to be controlled.
Which cry genes protect cotton and corn?
The proteins coded by the genes cryIAc and cryIIAb control cotton bollworms, while the protein coded by cryIAb controls the corn borer. The gene is written in italics with a small c, and the protein it codes is called a Cry protein. Exam options often swap these gene names.
How does RNA interference protect tobacco from nematodes?
Nematode-specific genes were introduced into tobacco using Agrobacterium vectors. They produced sense and anti-sense RNA, which paired to form double-stranded RNA. This dsRNA started RNAi and silenced a specific mRNA of Meloidogyne incognita, so the parasite could not survive in the transgenic roots.
What is totipotency, and how is it used in micropropagation?
Totipotency is the capacity to generate a whole plant from any cell or explant. In micropropagation, explants grown in a sterile nutrient medium give thousands of plants in a short time. These plants are somaclones, genetically identical to the parent, and tomato, banana and apple are produced this way.
How are virus-free plants obtained?
Even when a plant is infected with a virus, its apical and axillary meristems remain free of the virus. The meristem is removed and grown in vitro to obtain virus-free plants. Meristems of banana, sugarcane and potato have been cultured successfully in this way.
What is a somatic hybrid? Give an example.
A somatic hybrid is a plant grown from a hybrid protoplast, formed by fusing naked protoplasts of two varieties that each have a desirable character. The process is somatic hybridisation. The pomato, from tomato and potato protoplasts, is an example; it did not have all the desired characters, so it was not used commercially.
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