Cassava biotechnology: embryo culture/rescue and identification of RAPD Markers linked to the Pubescent Trait in Cassava.

Man has always depended on plants and animals for food and other useful products like hide, shelter and medicine. For this reason, plants and animals have been manipulated in one way or the other by man for his use. In ancient times the early man collected what they needed for their survival from the environment and soon started to domesticate those ones they needed most. Domestication was based on keen observation and selection of those plants and animals with desirable characteristics. This process of selection based on the phenotypic characteristics of the organism has been the rule even in present plant and animal breeding. Gradually people started to study the biological basis of life and Mendel found that those characters that were selected for are controlled by certain factors present in the organism, and in 1866 postulated a set of rules to explain the inheritance of biological characteristics in living organisms. These factors responsible for the characteristics of organisms are known as genes and in 1903, Sutton postulated that genes are located on chromosomes. As people progressively began to understand the factors and mechanisms that control biological processes, they began to manipulate them to improve performance, and eventually the sciences of breeding and genetics were born. Studies on the biological basis of life did not end afer the discovery of genes and in 1944 genes were found to be composed of eoxyr1bofluCleic acid (DNA). The DNA provides the instruction template for control of cellular functions. DNA is transcribed into RNA and RNA is translated into proteins that carry out the processes necessary for cell growth and maintenance. The discrete units of information encoded by DNA are what Mendel referred to as genes. Now, techniques are available which enable genes to be modified more directly than ever realised. This and others constitute a new technology that has emerged called biotechnology; it comprises many modern technologies developed from information accumulated over years of scientific advancement in biology and genetics. Simply, biotechnology can be defined as “the application of biological knowledge for a useful end (Jones, 1990). Biotechnology has also been defined by the Office of Technology Assessment of the United States Congress as “any technique that uses living organisms or substances from those organisms to make or modify a produce, to improve plants or animals, or to develop microorganisms for specific uses’’ (OTA, 1989) . From these definitions it is evident that biotechnology has been practiced for centuries. Thus, it comprises a continuum of technologies ranging from the long-established and widely-used technologies, which are based on the commercial use of microbes and other living organisms (e.g. brewing, food fermentation, conventional vaccine production etc.) through to the more strategic research on genetic engineering of plants and animals. The long-established and widely-used technologies can be referred to as “traditional” biotechnology, while recombinant DNA technology, monoclonal antibodies, cell and tissue culture, etc. can be referred to as “modern” biotechnology (Jones 1990; Persley 1990; Persley 1992). This continuum of technologies has been illustrated very well by Jones, 1990 in the form of a gradient in which the slope rises from the beneficial micro-organisms in biological nitrogen fixation through tissue culture and protoplast culture to the more complex genetic engineering in which scientists modify an organism by transferring very specific genetic information from one organism into another by direct DNA insertion. In some textbooks however, no clear distinction is made between “traditional” and “modern” biotechnologies, but definitions are limited only to the ‘high tech’ biotechnologies. For the purpose of this work, only the new biotechnologies which are based primarily on advances in cell and molecular biology and their use in crop improvement will be discussed.

Source: KNUST