Bio Technology and Genetic Engineering
Tissue culture is the growth of tissues and/or cells separate from the organism. This is typically facilitated via use of a liquid, semi-solid, or solid growth medium, such as broth or agar. Tissue culture commonly refers to the culture of animal cells and tissues, while the more specific term plant tissue culture is used for plants.
Genetically modified food
Genetically modified (GM) foods are foods derived from genetically modified organisms. Genetically modified organisms have had specific changes introduced into their DNA by genetic engineering, unlike similar food organisms which have been modified from their wild ancestors through selective breeding (plant breeding and animal breeding) or mutation breeding.
GM foods were first put on the market in the early 1990s. Typically, genetically modified foods are transgenic plant products: soybean, corn, canola, and cotton seed oil, but animal products have been developed. For example, in 2006 a pig engineered to produce omega-3 fatty acids through the expression of a roundworm gene was controversially produced. Researchers have also developed a genetically-modified breed of pigs that are able to absorb plant phosphorus more efficiently, and as a consequence the phosphorus content of their manure is reduced by as much as 60%.
Critics have objected to GM foods on several grounds, including perceived safety issues, ecological concerns, and economic concerns raised by the fact that these organisms are subject to intellectual property law.
Safe movement of germplasm
Collecting, conservation and utilization of plant genetic resources are essential com¬ponents of any crop improvement programme. Inevitably, the movement of germplasm involves the risk of accidently introducing 'pests' along with the host plant material. Many viruses, viroids and virus-like pathogens may exist in crops without showing obvious symptoms. Visual inspection of symptoms of virus dis¬eases is usually inadequate when selecting virus-free plants. Therefore, appropriate indexing methods are essential. Methods of biological virus indexing depend on the species concerned and include sap transmission to susceptible hosts, grafting and vector transmission. However, biological indexing needs special kind of green-house facilities and are time consuming. Undoubtedly, the most important development in virus indexing of genetic stock material in recent years has been the introduction of the enzyme-linked immunosorbent assay (Clark and Adams, 1977; Mowat and Dawson, 1987); dsRNA analysis (Morris & Dodds, 1979); Immunosorbent electron microscopy (Roberts et aI, 1982) and dot-blot nucleic acid hybrization (Gould and Symmonds, 1983). These methods are considerably more sensitive than other assay methods. Out of these methods enzyme linked immunosorbent assay (ELISA) has been used widely for surveys, seed and planting material certification and eradica¬tion work as well as for research. The use of virus-free plants to replace infected clonal material has already made a considerable impact on horticulture throughout the world by improve¬ments in yield and quality. To achieve this same goal in Sri Lanka, virus indexing methods should be adopted and practiced. These techniques could be adopted to ensure the safe movement of planting material both nationally and internationally.Presented below is an overview of the research findings at RARDC Bombuwela in a limited range of horticultural crops where the emphasis has been to develop virus detection techniques. These techniques are most suitable for adoptation in the programme of disease indexing where the primary objective is to generate germplasm Resources free of any biotic stresses.
E. M. Dassanayake Regional-Agricultural Research and Development Centre, Bombuwela
Crop wild relatives
A crop wild relative (CWR) is a wild plant closely related to a domesticated plant. It may be a wild ancestor of the domesticated plant, or another closely related taxon.
Conservation of crop wild relatives
CWRs are essential components of natural and agricultural ecosystems and hence are indispensable for maintaining ecosystem health. Their conservation and sustainable use is very important for improving agricultural production, increasing food security, and maintaining a healthy environment. The natural populations of many CWRs are increasingly at risk. They are threatened by habitat loss through the destruction and degradation of natural environment or their conversion to other uses. Deforestation is leading to the loss of many populations of important wild relatives of fruit, nut, and industrial crops. Populations of wild relatives of cereal crops that occur in arid or semi-arid lands are being severely reduced by over grazing and resulting desertification. The growing industrialization of agriculture is drastically reducing the occurrence of CWRs within the traditional agro-ecosystems. The wise conservation and use of CWRs are essential elements for increasing food security, eliminating poverty, and maintaining the environment.
Plant breeding is the art and science of changing the genetics of plants for the benefit of humankind. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to more complex molecular techniques. Plant breeding has been practiced for thousands of years, since near the beginning of human civilization. It is now practiced worldwide by individuals such as gardeners and farmers, or by professional plant breeders employed by organizations such as government institutions, universities, crop-specific industry associations or research centers. International development agencies believe that breeding new crops is important for ensuring food security by developing new varieties that are higher-yielding, resistant to pests and diseases, drought-resistant or regionally adapted to different environments and growing conditions.