Applications of Biotechnology in Agriculture

The following points highlight the four main applications of biotechnology in agriculture:- 1. Micro-propagation 2. Induction and Selection of Mutant 3. Production of Somatic Hybrids 4. Production of Transgenic Plants.

Application # 1. Micro-propagation:

Mass propagation of crop and forest plants is an important applica­tion of micro-propagation technique. The deve­lopment of embryos from somatic cells in culture resulted in artificial seed production.

This tech­nique involves three stages:

(a) Establishment of culture

(b) Regeneration of plants

(c) Transfer of plants from test tube to soil

Regeneration of plantlets in cultured plant cell and tissues has been achieved in many trees of high economic value. Many of the studies are aimed at large scale micro-propagation of impor­tant trees yielding fuel, pulp, timber, oils and fruits.

Therefore, clonal forestry and horticulture are gaining an increasing recognition as an alter­native for tree improvement. In recent years, the interest has aroused in commercializing the in vitro propagation of forest trees.

This will bring about refinement in the existing procedures to make micro-propagation more cost effective. For betterment and improvement of tree plants of high economic value, genetic transformation and in vitro regeneration have been done in many angiospermic and gymnospermic plants.

Application # 2. Induction and Selection of Mutant:

Different physical and chemical mutagens are used in the plant explants of different species to generate mutants. Now the mutants can be used to select out the variant cell lines which are resistant to antibiotics, amino acid analogues, chlorate, nucleic acid base analogue, fungal toxin, environmental stresses (salinity, chilling, high temperature, aluminum toxicity) and herbi­cides, etc.

Single cell or the protoplast culture systems have proved to be valuable for muta­genesis since the presence of discrete cells in these substances is more effective to cause muta­tion, and isolation of mutant line is more easier.

Application # 3. Production of Somatic Hybrids:

The pro­toplasts can undergo fusion under certain favou­rable conditions and the fused product can give rise to somatic hybrid plant which offers:

(a) The possibility of hybrid formation of widely unrelated forms,

(b) An asexual means of gene transfer either of whole genome or of partial genome.

Through successful production of hybrid plants at the tetraploid and hexaploid levels, both for inter- and intra-specific fusions, charac­ters from sexually incompatible wild species are transferred to the cultivar.

Other approaches to genetic manipulation include the irradiation of donor protoplasts with useful characters, to frag­ment their genomes, followed by fusion to tetraploid acceptor protoplasts. Protoplast fusion also provides a means of transferring cytoplasmic traits into another genomic background.

Inter-generic somatic hybrids have been pro­duced in many genera like ‘Raphanobrassica’, obtained through fusion between Raphanus sativus and Brassica campestris, ‘Solanopersicon’, obtained through fusion between Solanum tuberosum and Lycopersicon esculentum, etc.

The technique of cybrid pro­duction has been utilized for transfer of cytoplas­mic male sterile character, as has been done in case of Nicotiana, Brassica and Petunia.

Application # 4. Production of Transgenic Plants:

Genetic engineering can be used to introduce genes into a plant, which do not exist in any member of the same plant family.

If genetically engineered plants are to be used commercially, then the following criteria are to be satisfied:

(a) Introduction of the gene(s) of interest to all plant cells;

(b) Stable main­tenance of the new genetic information;

(c) Trans­mission of the new gene to subsequent gene­rations;

(d) Expression of the cloned genes in the correct cells at the correct time.

A number of useful traits, mostly single gene, that have been transferred to get the transgenic for various purposes are:

(i) Insect-pest resistance plants:

Using gene transfer technique the Bt. gene (Cry I protein from Bacillus thuringiensis) has been transferred to many crop plants like rice, cotton, tomato, pota­to, etc. and insect resistant plants (Bt. crops) have been developed.

(ii) Herbicide resistant plants:

Using biotechnological approaches many herbicide resistant crop plants have been obtained as in Brassica, tomato, corn, cotton, soya-bean, etc. which are resistant against glyphosate (Roundup), L-phosphinothricin (Basta), etc.

(iii) Virus resistant plants:

Viral coat protein genes can be introduced to get the virus resistant plants as has been done in tomato, potato, squash, papaya, etc.

(iv) Resistance against bacterial and fungal pathogens:

Several examples are available where the transgenic plants against bacterial and fungal pathogens have been developed. The chitinase gene have been introduced in tobacco to get the resistance against brown spot; acetyl transferase gene has been introduced in tobacco to get the resistance against wild fire disease.

(v) Improvement in nutritional quality:

Nutritional quality can be improved by introduc­ing the genes for production of cyclodextrins, vita­mins, amino acids, etc.

Transgenic potato has been obtained to produce cyclodextrin molecule; the transgenic rice named as ‘Golden rice’ has been obtained to produce pro vitamin-A which has opened the way for improving the nutritional stan­dards; Ama-I gene has been introduced in potato. Starch content has been increased in transgenic potato.

(vi) Quality of seed-protein and seed-oil:

Recombinant DNA technology has been used successfully for improvement of protein quality in seed as has been done in pea plant which is rich in sulphur containing amino acids; lysine rich cereals have also been produced.

Oilseed rape has been made transgenic which has the modified seed oil quality, i.e., low erucic acid. Reduced linolenic acid containing flax and high stearic acid containing soya-bean and safflower also have been produced.

(vii) Improvement of quality for food- processing:

‘Flavr-Savr’ variety of tomato has been raised which shows bruise resistance as well as delayed ripening.

(viii) Male sterility and fertility restoration in transgenic plants:

Male sterile transgenic plants have been produced with ‘barnase’ gene which has the cytotoxic product tagged with anther spe­cific TA-29 promoter, and another set of plants have been produced to restore the fertility factor with the help of ‘barstar’ gene tagged with the same promoter. F₁ hybrids from these two sets of transgenic should facilitate the hybrid seed pro­duction for crop improvement.

(ix) Production of stress tolerant:

Several projects are going on for transgene application to develop the tolerance against different abiotic stresses, e.g., cold (tobacco), drought (mustard), salt (rice).