Cereals are grasses with huge seeds around them. After undergo some processes, cereal considered as nutritious food and give many benefits to human in the daily diet by providing carbohydrates and proteins (Varshney et al 2006). Cereals play an important role in the staple foods since their domestication (Varshney et al 2006). Besides that, cereals also best known as cultivated plants for food production (Varshney et al 2006). Examples of cereals are rice, barley, rye, wheat, maize and sorghum (Varshney et al 2006).
Nowadays, several methods for gene transfer to cereal have been used to produce transgenic strains of different types of cereals for various purposes (Komari et al 1998). The initial material to conduct the transformation of cereals will be the immature embryos and the bar gene contains phosphinothricin acetyltransferase used as selective marker (Komari et al 1998). One of the popular methods will be direct transformation method that used particles bombardment to transform the plant materials directly (Komari et al 1998). In order to transfer the genes into cereals, selected tissues are bombarded with highly accelerated particles coated with DNA (Komari et al 1998). Cereals that hardly regenerate such as rice and sorghum will be involved in such method to produce transgene (ePlantScience.com 2009).
Figure 1: Particle bombardment gun
Besides that, Agrobacterium-based system also used to conduct the transformation of cereals (Komari et al 1998). This method allows the transfer of huge amount of DNA and integration of small amount of genes copies into the plant chromosomes (Shrawat 2007). As a result, transgenic plants with higher quality and stability are produced (Komari et al 1998). Examples of successful cereal using Agrobacterium-mediated transformation are wheat, barley and maize (Shrawat 2007). The transformation occurred between the host and pathogen with the initiation compound of acetosyringone which is produced by the wooden plant cells (Australian Society of Plant Scientist et al 1999). This causes the T-DNA genes to be expressed after introduced into the host genome which is also known as agroinfection (Komari et al 1998). Pathogenic T-DNA genes are replaced with genes for desirable economic traits (Australian Society of Plant Scientist et al 1999).
Figure 2: Agrobacterium-mediated transformation
(Australian Society of Plant Scientist et al 1999)
Among the cereals, sorghum grain is mostly used by consuming it in the form of flat breads and porridges (Kumar et al 2011). Sorghum distributes the seeds itself which is diploid with a genome (Kumar et al 2011). The genome size of sorghum is 0.8 x10^9 (Varshney, 2006). Genetic enhancement of sorghum enables it to adapt and grow in drought environment, produces higher amount of grains, ability to resistant towards shoot fly during the rainy season and tolerance with the grain mold due to the hardness of grain (Kumar et al 2011). However, the grain mold resistance mostly found in the coloured grain sorghums (Kumar et al 2011).
In conclusion, cereals are the dietary staple in most of the countries. Cereals provide vitamins, energy, proteins and fats that is important to human. In order to improve the quality and increase the proportion of cereals, scientists have conducted several researches on cereals so that the genes can be transferred to the cereals. Finally, a new product will be produced.
Ashok Kumar, Belum Venkata Subba Reddy, Hari Chand Sharma, Charles Thomas Hash, Pinnamaneni Srinivasa Rao, Bhavanasi Ramaiah, Pulluru Sanjana Reddy. 2011. Recent Advances in Sorghum Genetic Enhancement Research at ICRISAT. American Journal of Plant Science, vol.2, pp.589-600.
Ashok K. Shrawat 2007, Genetic transformation of cereals mediated by Agrobacterium: potential and problem, viewed 12 April 2012, <http://www.nbiap.vt.edu/articles/feb0703.htm>
Australian Society of Plant Scientists, New Zealand Society of Plant Biologists, and New Zealand Institute of Agricultural and Horticultural Science 1999, Transformation system, viewed 12 April 2012, <http://plantsinaction.science.uq.edu.au/edition1/?q=content/10-4-1-transformation-systems>
ePlantScience.com 2009, Particle bombardment gun, viewed 12 April 2012, < http://www.eplantscience.com/index_files/biotechnology/Genes%20&%20Genetic%20Engineering/Techniques%20of%20Genetic%20Engineering/biotech_particle_bombardment.php>
Rajeev K. Varshney, David A. Hoisinton, Akhilesh K.Tyagi. 2006. Advances in Cereal Genomics and Applications in Crop Breeding. Trends in Biotechnology, vol.24, no11.
Toshihiko Komari, Yukoh Hiei, Yuji Ishida, Takashi Kumashiro, Tomoaki Kuba. 1998. Advances in Cereal Gene Transfer. Current Opinion in Plant Biology, vol.1, pp.161-165.