The use of chemical insecticides to kill insect pest infesting the corn plants has proliferated current devastating state of the environment and the ecosystem at large. Corn plant is one of the most important crops in the world due to its wide array of uses. However, a number of factors such as infestation by pest and diseases have threatened the existence of the corn plant by lowering its yield and productivity. Even though many farmers had embraced the use of insecticides to control insect pests, this mechanism has not fully benefited man and the environment. It is with this profound reason that a vast majority of erudite scientists did a research on ways of replacing chemical insecticides with a biological control agent. Plant genetic transformation technologies werethus used to completely transform and protect the corn plant from insect pests. It is with this reason that Bacillus thuringiensis bacteria had been assorted as the main organism that would help in combating the problem of pest infestation to the corn plants(Mihm& International Maize and Wheat Centre, 1997).
Bacillus thrungiensisis bacteria whose major habitat is soil. This species of bacteria has been employed as a primary biological control agent for a wide range of pests and insects. This is due to the unique trait of Bacillus thuringiensis being able to produce specific kind of proteins that kill certain type of insects by disrupting the digestion systems of the insect leading to the insect’s slow growth and ultimately death. It is with this reason that scientists used the technique of genetic engineering so as to perform genetic transformation of the corn plant. Genetic engineers can engineer a gene encoding the toxic factor able to infect different plant pests(Carswell et al., 1997).
Before genetic engineering takes place, it is prudent for the researcher to first look for the specific strain of Bacillus thuringiensis with the desired trait of providing the corn plant resistance against insect pests. This is then followed by DNA extraction process where the desired DNA is extracted from Bacillus thuringiensis. The next step involves cloning the specific gene for the Bacillus thuringiensis protein. Gene cloning is done specifically to separate the single gene of interest from the rest of genes that had been extracted during the process of DNA extraction. In order for the gene to be successfully inserted into the corn plant, it must first be restricted in a test tube using specific restriction enzymes. This is later followed by transformation or gene insertion process which can be done through either using the vectors, gene gun, electroporation or microfibers. This is done for the sole purpose of transporting the new gene to the corn plant. Whilst using the gene gun method of gene insertion, the Bt protein gene must first be coated with microscopic gold particles where one shoots so as to transfer the DNA into the nucleus of the corn plant. The transformed corn plant cells are then regenerated into transgenic plants. The transformed cells are the placed on nurse cell cultures where the cells will receive an adequate supply of nutrition and conducive osmotic environment. A selective agent is also introduced to the nursery cell culture so as to kill the non-transgenic or corn plant cells that had not undergone transformation (De Greve et al., 1993). Specific type of herbicide may also be sprayed on the growing Bt-corn plants so as to eliminate the corn plants that had not undergone gene insertion. The final step is the backcross breeding where the transgenic t corn plants are crossed with elite breeding lines using traditional breeding methods. The offspring are repeatedly crossed back to the elite line so as to obtain a high yielding transgenic corn plant. Field testing may also be done to check whether the corn plants have been transformed to be resistant against insect pests such as European corn borer, caterpillar or beetles.
The potential impact of Bt-corn plant on the individual agricultural system is that it is environmentally friendly. This is because Btcorn plant produce proteins with insecticidal properties that target specific insect pests. Bt toxins produced by the transgenic corn plant target a narrow array to insects pests. The use of Bt toxin is convenient to the environment as the beneficial non target organisms are spared from the toxic effect of Bacillus thuringiensis. The use of chemical insecticides has been replaced with the use of Bacillus thuringiensis which acts as a biological control agent (Carswell et al., 1997). This is because the use of chemical insecticide is harmful to other beneficial organisms which contribute significantly to the stability of the ecosystem. Btcorn plant is therefore a safer to natural enemies as compared to conventional synthetic insecticides. This could further be used as part of Integration Pest Management as it is able to regulate pest population thus being a vital ecological service provider.
In conclusion, genetic engineering of the corn plant with Bacillus thuringiensis has provided a lasting solution to protect the corn plants, man and the ecosystem at large. Bt corn plant serves as an excellent biological control agent that has today been embraced by many farmers as a substitute of chemical insecticides. Therefore, man has been alleviated from negative health effects whilst the beneficial non target organisms have been protected from toxic insecticides thus bringing the ecosystem at equilibrium.
Question and Answers
- Compare and contrast the structure of teosinte with that of corn. Why did people believe that teosinte could not be the ancestor to corn? Why were its kernels probably not used to a great extent as food? (4 marks)
Teosinte has been regarded as being very closely related to the corn plant. This is because of the fact that they have the same number of chromosomes and similar gene arrangements. Teosinte has branched stem whereas a corn plant has a straight stem that is not branched. Besides this, a corn plant has a single stalk and ear per plant where as a teosinte has many stalks or tillers per plant. In addition, teosinte has many female ears and male ears per plant. The structure of the maize ear is very different from that of teosinte.In a teosinte, the pediculate spikelet is rudimentary or absent thus the seeds being produced in two single rows on distichous spikes whereas in a corn, both spikelet of each pair are sessile as each develops a single seed.
People believe that teosinte could not be the ancestor to corn due to their kernels being very different.
The kernels of teosinte cannot be used as food due to the existence of a hard coating called glume which covers the kernel thus making it difficult to chew and digest by humans (Mihm& International Maize and Wheat Centre, 1997).
- The movement of corn as a crop throughout the Americas was very slow. What accounts for this? (3 marks)
This is because the Native Americans could not use Teosinte for food consumption due to their small kernels and not fused together. It is with this reason that the Native Americans took a long time on research while employing scientific techniques to transform the Teosinte into maize that had longer ears and rows of kernels.
- What archaeological data was used to provide information on the domestication of corn? What did each type of information reveal? (3 marks) Archeo-botanical data
- The Tehuacan sequence represents a transitional form between teosinte and maize.
- The Tamaulipas sequence shows a series of phases of corn domestication from Tamaulipas(Bennetzen, 2009).
- How did the domestication of corn differ from that of wheat? Could Galinat’sscenario for corn be applied to the domestication of wheat? Explain your answer. (4 marks)
Domestication of corn began about ten thousand years ago in Mexico after the arising as a result of interbreeding of teosinte and maize. On the other hand domestication of wheat occurred approximately 11,000 years ago in the western arch of Fertile Crescent. Wild emmer wheat, Triticumturgidum ssp. dicoccides was the progenitor of modern wheat. Gailinat’s scenario cannot be applied to the domestication of wheat due to the fact that the modern wheat has been as a result of natural synthesis between a tetraploid wheat species; T. turgidum and diploid wheat species; T. tauschii.
- Explain why corn seed is most commonly purchased every year rather than saved from a previous year’s crop. (3 marks)
This is because famers are assured that a newly purchased seed is free from pathogens and diseases. Besides this, hybridized seeds are mostly purchased as opposed to being saved from a previous year’s crops due to their ability of producing more uniform and quality yield.
- What are the main differences between the Tripartite and the Teosinte theories? What type of information would provide evidence that would put to rest the controversy? (3 marks)
Tripartite theory suggests that maize and teosinte diverged before domestication and that maize had been domesticated from wild maize. In addition, the diversity of maize was assumed to have originated due to introgressive hybridization of genes from Tripsacum. On the other hand, teosinte theory hypothesized that teosinte was the progeny of a hybrid between maize and Tripsacum.
Recent research demonstrated that a strain of Teosinte plant is the direct ancestor of modern corn. This is because Teosinte still grows wild parts of Mexico’s western Sierra Madre. Besides this, the ear of the plant very much resembled the Teosinte ear that had been transformed by the Native Americans to the current corn ear. In addition, the ear of the found Teosinte plant is far different from the ear of the corn plant (Bennetzen, 2009).
Carswell, G., Harms. C., Chang, Y. F., & Chilton, M. D (1997). U.S. Patent No. 5,595,733, Washington, DC: U.S. Patent and Trademark Office.
De Greve, H. M., Salgado, M. B., Van Montagu, M. C., Vaeck, M. A., Zabeau, M.F., Leemans, J. J., &Leemans, J.J., &Hofte, H. F. (1993). U.S. Patent No. 5,254,799. Washington, DC: U.S. Patent and Trademark Office.
Bennetzen, J.L., & Hake, S. (2009). Handbook of Maize: Genetics and Genomics. New York, NY: Springer New York.
Mihm, J.A., & International Maize and Wheat Improvement Centre. (1997). Insect rtesistant maize: Recent advances and utilization: proceedings of an international symposium held at the International Maize and Wheat Improvement Center) CIMMYT), 27 November-3 December, 1994. Mexico City: CIMMYT.