Plant Biotechnology

Define plant biotechnology. Using examples discuss how it is different from traditional / conventional methods plant breeding. Plant biotechnology has been defined as the integrated use of biochemistry, microbiology and engineering sciences in-order to achieve technological application of micro-organisms and cultured tissue cells in the transfer of genetic traits from one crop species to another to obtain transgenic plants that are of beneficial use to human kind (Lawrence . W; 1968).

Heldt H and Heldt F (2005) defines plant biotechnology as the art and science to produce a genetically modified plant by removing genetic information from an organism, manipulating it in a laboratory and then transferring it into a plant to change certain of its characteristics. . Plant breeding is the science and art of improving crop plants through the study and application of genetics, agronomy, statistics, plant pathology, entomology, and related sciences (Kuckuck et al; 1991).

Increased crop yield is the primary aim of most plant-breeding programs; advantages of the hybrids and new varieties developed include adaptation to new agricultural areas, greater resistance to disease and insects, greater yield of useful parts, better nutritional content of edible parts, and greater physiological efficiency. Humans have been improving crops for yield and other characteristics since the advent of agriculture. Plant biotechnology involves processes such as genetic engineering which involves the direct addition of foreign gene/genes to the genome of an organism.

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It is a type of genetic modification. Traditional plant breeding also modifies the genetic composition of plants. It involves techniques such as crossing and selection of new superior genotype combinations. Firstly traditional methods tend to breed plants that can sexually mate with each other. This limits the new traits that can be added to those that already exist in that species. Secondly when plants are crossed, many traits are transformed along with the trait of interest. Whereas genetic engineering, on the other hand, is not bound by these limitations.

It involves the removal of a specific fragment of DNA from one plant or organism and transferring the genes for one of a few traits into another. No crossing is required hence the sexual barrier between species is overcome. It is more specific in that a single trait can be added to a plant (Bajaj . Y; 2001). According to Rost . T. I et al (2006), another difference between traditional plant breeding and plant biotechnology is the number of genes transferred to the offspring in each case. Plants contain approximately 80 000 genes which recombine during sexual hybridization.

The offspring may therefore inherit around 1000 new genes as a result of this recombination. This is equivalent to a 0. 0125 % change in the genome. By contrast when a specific gene is transferred into a plant, there is a 0. 0025% change in the genetic information of the plant, it is argued that plant biotechnology provides a more precise approach to crop improvements than sexual hybridization. Plant biotechnology through genetic engineering can cause harmful toxins to be produced by transformed plants, though it is still unclear whether it is due to the technique itself on the nature of the foreign gene.

The introduction of a gene that it is known to encode a toxin in one organism will induce a similar effect when introduced into a different organism (Raven P. H et al; 1992). There has been a case where a transgenic soybean containing a gene from Brazil nuts elicited an allergic reaction in some people. The gene from Brazil nuts had been well characterized and its product known to cause an allergy, hence extensive laboratory tests. This illustrates why rigorous characterization of a gene is required before permitting its introduction into a novel species.

However there is also the potential of toxic product being produced as a result of conventional methods of crop improvements. For example, in sweet potatoes where vegetative propagation is done, potato varieties with increased pest resistance have continually been selected as giving a higher crop variety. Those varieties contain high levels of natural pesticides, called glucoalkaloids. However these compounds are toxic to animals, so could have harmful effects when eaten.

This demonstrates that the nature of the novel feature should be open to debate rather than the method by which it is introduced (Lawrence . W; 1968). The traditional methods of crop improvements are limited by the sexual compatibility of the plants involved; whereas with plant biotechnology through genetic engineering any characteristic from any organism of any species can be introduced into a plant. Plant breeders therefore have access to a much wider gene pool than they have using traditional crossing methods to develop a new variety.

For example a rice gene responsible for defense against a disease causing fungus can be transferred to a banana susceptible to that disease. The intent is to protect the genetically modified banana from that disease and thereby reduce yield loss and number of fungicide applications. Another example is that genes introduced into plants to provide a resistance to the herbicide Round Up was isolated from bacteria. An insecticidal toxin used as a crop spray was also extracted from bacteria. Genetically modified maize is been grown which expresses this type of proteins.

One major difference between traditional plant breeding and plant biotechnology; genetic engineering/ modification is that, while extensive restrictions are in place to limit the development and release of genetically modified varieties, those developed by sexual hybridization and mutagenesis are under no restrictions (Raven P. H et al; 1992). A major concern surrounding the cultivation of genetically modified crops is the possibility of cross pollination between transgenic and related crops.

While this is clearly possible for some species, but not all crop species have native wild relatives with which they are sexually compatible meaning that the possibility of the production of “super weeds” is not possible. Plants such as carrots are allowed only to flower for seed production meaning that cross-pollination during normal commercial cultivation is unlikely. In plant biotechnology plants can be grown in artificial medium requiring less land mass to produce large amounts of crops in less time. Although it seems like a great alternative to the earlier methods, it can also be devastating.

By growing plants at a faster rate there is a possibility of losing the essential vitamins and nutrients that are important for us. Transgenic plants are still a relatively new field and no concrete evidence for any of this existing but it is growing concern (Bajaj . Y; 2001). Heldt . H and Heldt . F (2005) says, the techniques of traditional breeding are very time-consuming. By making crosses, also a large number of undesired genes are introduced into the genome of the plant. The undesired genes have to be "sorted out" by back-crossing.

Using plant biotechnology which involves the use of Restriction Fragment Length Polymorphism it greatly facilitates/substitutes conventional plant breeding, because one can progress through a breeding program much faster, with smaller populations and without relying entirely on testing for the desired phenotype. RFLP makes use of restriction endonucleases enzymes which recognize and cut specific nucleotide sequence in DNA. The cut fragments are separated according to size by gel electrophoresis and made visible by hybridizing the plant DNA fragments with labeled DNA probes.

The closer two organisms are related, the more pattern of bands overlap. With conventional breeding, the pool of available genes and the traits they code for is limited due to sexual incompatibility to other lines of the crop in question and to their wild relatives. This restriction can be overcome by using the methods of genetic engineering, which in principle allow introducing valuable traits coded for by specific genes of any organism (other plants, bacteria, fungi, animals, viruses) into the genome of any plant. According to Rost . T. I et al (1992), transgenes are inserted into the nuclear genome of a plant cell.

Recently it has become possible to introduce genes into the genome of chloroplasts and plastids. Transgenic plants have been generated using methods such as agrobacterium-mediated DNA transfer, direct DNA transfer, particle bombardment and electroporation. References 1. Bajaj . Y. (2001). Transgenic Crops. Berlin. Springer. 2. Heldt . H and Heldt . F. (2005). Plant Biochemistry. 3rd edition. California. Elsevier. 3. Kuckuck . H; Kobabe G. and Wenzel G. (1991). Fundamentals of plant breeding. New York. Springer-Verlag. 4. Lawrence . W. (1968). Plant breeding. London. Edward Arnold Publishers Ltd. 5. Raven P.

H, Evert . R. F and Eichron . S. E. (1992). Biology of Plants. 5th edition. New York. Van Hoffman Press Inc. 6. Rost . T. l. , Barbour . M. G. , Stocking . R. C. and Murphy . T. M. (2006). Plant Biology. 2nd edition. California. Thomson Brooks/Cole. CHINHOYI UNIVERSITY OF TECHNOLOGY NAME: Tanyaradzwa R Ngara REG NUMBER: C1110934J COURSE:Plant Biotechnology COURSE CODE: CUBT 207 PROGRAM:BSBIO Assignment: Define plant biotechnology. Using examples discuss how it is different from traditional / conventional methods plant breeding [25marks].

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