Bioscience in brief
Traditional crop breeding involves a number of techniques aimed at changing the genetic make-up of plants to make them better crops. Yield and nutritional quality, tolerance to drought, and resistance to pests and diseases are the most common characteristics which have been improved.
Variation in the characteristic a breeder wishes to improve is sometimes found in individuals within a population. In cases where the required variation is not available within a species or variety (the recipient), breeders look for it in closely or distantly related plant species (the donor) which are capable of cross breeding and producing fertile seeds. The donor and recipient plants are crossed, and the progeny are screened and selected for plants with the improved characteristic. Since many characteristics of the donor plant besides the desired characteristic will also have been inherited, breeders need to cross the selected descendants to the donor parent crop for at least 8 to 10 generations: this is called backcrossing. It aims to remove the unwanted genetic contributions from the donor plant while retaining the desirable characteristics of the original recipient/parent line. Backcrossing and selection is repeated many times and makes traditional breeding a lengthy process as you have to grow the plants of each generation until they are mature and capable of producing seed, but a very effective one too - all the food, feed and fibre plants available to us until the middle of the 20th century were developed this way, and today’s crops still depend on it.What is a GM crop?
GM organisms are ones that have been modified through the insertion of genes from other organisms using the techniques of genetic engineering. While the source of variation in conventional breeding is limited to a crop and its related species, due to the universality of the genetic code GM technology enables plant breeders to bring together in one plant useful genes from a wide range of sources, not just from within the crop species or from closely related plants.
For example, to develop East African Highland plantains that are resistance to bacterial wilt, scientists have been able to use a gene from sweet pepper. Resistance to this disease, which costs farmers in Africa's Great Lakes region an estimated half a billion dollars every year, cannot be addressed by conventional breeding because bananas are sterile.
GM crops are made by inserting a gene or genes conferring desirable characteristics, such as insect resistance or higher level of micronutrients, into the DNA of crop plants. Two methods currently exist for introducing transgenes into plant genomes. The first method involves a device called a ‘gene gun’ which is used to fire into plant cells heavy metal particles coated with DNA containing the desirable gene(s), some of which will be incorporated into the plant’s chromosomes and inherited. The second technique uses a commonly found soil bacterium to introduce the genes(s) of interest into the plant chromosomes, in a process called transformation.What is genetic engineering?
This is another term for gene technologies, or genetic modification (GM). GM alters the genetic makeup of an organism using techniques that introduce heritable material (called a transgene) prepared outside the organism either directly into the host or into a cell that is then fused or hybridized with the host.What is marker-assisted selection (MAS)?
MAS combines traditional breeding techniques with modern molecular biology techniques. Genetic markers are pieces of the DNA sequence which have an identifiable physical location on a chromosome. The purpose of using them is to monitor how they are inherited from one generation to another. Markers provide a way to indirectly select a gene in the progeny of a sexual cross that codes for/contains the information for a desirable characteristic, and therefore they make traditional breeding both more precise, and much faster. For example, developing a new crop variety with conventional breeding techniques alone can in some cases take up to 20 years. MAS helps shorten this time to less than 10 years with less expense. MAS is particularly useful for selecting complex genetic characteristics that involve multiple genes which applies to most useful traits.What is crop biofortification?
Biofortification refers to a breeding method aimed at producing health-promoting foods by improving the nutritional value of crops, typically by increasing the content of proteins, essential vitamins and essential elements such as iron. Biofortification can be achieved by conventional breeding methods by crossing high yielding varieties with high nutrient varieties of crops. An example of a conventional biofortified crop is Orange Fleshed Sweet Potato which has higher vitamin A content than ordinary sweet potatoes. Golden Rice which contains high levels of Vitamin A has been developed by genetic modification a sit is not possible to produce such rice by conventional plant breeding. Both these crops are the product of partnerships between publicly funded research organisations and private companies. Golden Rice will not be more expensive for farmers than conventional rice when it becomes available to farmers. Once Golden Rice can be grown commercially it is expected that seed will be made freely available by international seed companies.Who makes GM crops?
The first GM crops commercialised were produced by large and often multinational private sector companies. The first generation GM crops affect what are called input characteristics, that is, how plants are grown. The most common characteristic is herbicide resistance, followed by insect tolerance, and by “stacked” characteristics that combine insect tolerance and herbicide resistance. Herbicide tolerance means that the GM crop is resistant to a herbicide spray which will kill off all other plants (weeds) in the field. Insect resistance means that the GM crop is resistant to pests and diseases that will otherwise destroy or diminish the crop’s yield and performance. The most common GM crops grown in terms of acreage are soybean, oilseed rape, maize and cotton.
However, a large number of second-generation GM crops are under development, and many of these are being produced by the public sector, by private-public partnerships including not-for-profit initiatives. Examples include Golden Rice, with higher vitamin A content; insect-resistant aubergine; virus resistant cassava; banana resistant to black Sigatoka virus and weevils; and insect resistant pigeon pea, among others.Are GM crops sterile?
The characteristics of a given GM crop will depend on the nature of the transgene introduced. To date no sterility genes have been engineered into crop plants.What are suicide seeds / terminator technology?
Terminator technology is used to refer to one of the proposed applications of Gene Use Restriction Technologies (GURTs) which limits the use of GM crops by causing second generation seeds to be sterile. This is why they are called ‘suicide seeds’. Development costs for a new GM crop run into millions of dollars so the use of GURTs was seen as an effective way of enforcing the Intellectual Property Rights (IPR) of the company that developed the GM crop, since it would entail farmers having to buy new seeds each year instead of saving them one year to the next. This would also be a way for companies to recoup their development costs. The patent for the technology was jointly field by the United States Department of Agriculture and a company called Delta Pine in 1998. Monsanto acquired the technology when it took over Delta Pine in 2006.
GURTs have never been used commercially.
Terminator technology sparked an enormous amount of controversy which led the United Nations Convention on Biological Diversity to recommend a de facto moratorium on the commercial use of the technology in 2000. Main critiques are fears of monopoly of the food production by biotech seed companies; and the serious threat this would represent to the livelihood of resource-poor farmers in developing countries.
Hybrid seeds are produced by crossing two parent lines that are genetically different from each other. The seeds produced by this cross (called the F1 generation), the hybrids, have uniform characteristics that typically perform better than the parent due to a process known as “hybrid vigour”. Hybrids are not sterile but if the seeds are saved and sown the next generation they will no longer be the same because the genes re-sort themselves during reproduction. As a result the crop is more difficult for the farmer to tend as plants are likely to differ in size, and to mature and fruit at varying times. For this reason farmers prefer to buy new seeds each year since the higher cost of seeds is offset by the increased performance/productivity and ease of management of the crop.How are GM crops regulated?
The global legal and regulatory framework surrounding GM crops is built upon two international United Nations commitments – the Convention of Biological Diversity (CBD) of 1993 and the Cartagena Protocol on Biosafety (CP) of 2000. The former is an international commitment to the conservation of biological diversity, sustainable use of biological resources, and sharing equitably the benefits arising from the use of genetic resources. The latter is an international regulatory framework that reconciles the respective needs of trade and environmental protection with respect to trans-boundary movement of genetically modified organisms (GMOs). Countries that sign and ratify the Cartagena Protocol accept being bound by the provisionsWhich GM crops are grown in Africa?
Currently only three African countries have approved GM crops for cultivation: South Africa (since 1996; maize, soybean and cotton), Burkina Faso (since 2008; cotton) and Egypt (since 2008; maize).
African countries that have enacted Biosafety legislation for the confined field testing of GM crops include Nigeria, Ghana, Kenya, and Uganda.
Genes are the fundamental physical and functional units of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (a protein or an RNA molecule).What is a genome?
All the genetic material in the chromosomes of a particular organismFor any more information on B4FA feel free to contact us