Microbiology is one of the Biology Topics that involves the study of microorganisms, including bacteria, viruses, and fungi.
Biofortification Methods in Improving Nutritional Value to Crops
Biofortification is the idea of breeding crops to increase their nutritional value. This can be done either through conventional selective breeding or through genetic engi¬neering. Biofortification differs from ordinary fortification because it focuses on making plant foods more nutritious as the plants are growing, rather than having nutrients added to the foods when they are being processed. This is an improvement on ordinary fortification when it comes to providing nutrients for the rural poor, who rarely have access to commercially fortified foods. As such, biofortification is seen as an upcoming strategy for dealing with deficiencies of micronutrients in the developing world. The breeding programme in crop plants that increases levels of minerals, vitamins, complete proteins, and healthier fats is called biofortification.
Many people in the world suffer from the lack of adequate food still today. This is not only due to the amount of food but also to the quality of their nutrients. Nutrients are deficient in several proteins, vitamins, or micronutrients. Lack of essential nutrients, especially iron, vitamin A, iodine, and zinc increases proneness to disease and reduces mental abilities and life span. It is therefore important to enhance nutritional quality of the crops. Hence, a breeding programme for enhanced nutritional quality is undertaken to improve-
- Protein content and quality (for essential amino acids).
- Oil content and oil quality (for essential fatty acids).
- Higher vitamin content.
- Higher micronutrient and mineral content.
It has been possible to develop maize hybrids that had twice the amount of lysine and tryptophan as compared to the existing maize hybrids. The trait for high protein content of Atlas 66 (wheat variety) has been transferred to the present-day cultivated varieties. Another development is that of rice variety including five times more iron than the commonly consumed varieties. IARI (Indian Agricultural Research Institute), New Delhi, has also developed many vegetable crops that are rich in minerals and vitamins. These are vitamin A-enriched carrots, spinach, and pumpkin; vitamin C-enriched bitter gourd, tomato, mustard, etc., calcium and iron-enriched spinach, and chenopodium and protein-enriched beans.
Plants are bred using one of two main methods:
1. Selective Breeding:
Using this method, plant breeders search seed germplasm banks for existing varieties of crops that are naturally high in nutrients. They then crossbreed these high-nutrient varieties with high-yielding varieties of crops, to provide seed with high yields and increased nutritional value. Crops must be bred with sufficient amounts of nutrients to have a measurable positive impact on human health. As such, they must be developed with the involvement of nutritionists whether the consumers of the improved crop can absorb the extra nutrients and the extent to which storage, processing, and cooking of the crops affect their available nutrient levels. This method is prevalent at present, as it is quicker, cheaper, and less controversial than genetically engineered crops. For example, Harvestplus, a major NGO in the development of biofortified crops primarily uses conventional breeding techniques and has not yet spent more than 15% of its research budget on genetically modified crops when conventional methods fail to meet nutritional requirements.
2. Genetic Modification:
Golden Rice is an example of a GM crop developed for its nutritional value. The latest version of Golden Rice contains genes from a common soil bacterium Erwinia and maize and contains increased levels of beta-carotene which can be converted by the body into vitamin A. Golden Rice is being developed as a potential new way to address vitamin A deficiency.
Uses of Biofortification
Deficiencies of various micronutrients, including vitamin A, zinc, and iron are common in the developing world and affect billions of people. These can lead to, amongst other symptoms, a higher incidence of blindness, a weaker immune system, stunted growth, and impaired cognitive development. The poor, particularly the rural poor, tend to subsist on a diet of staple crops such as rice, wheat, and maize, which are low in these micronutrients and most cannot afford or efficiently cultivate enough fruit, vegetables, or meat products that are necessary to obtain healthy levels of these nutrients. As such, increasing the micronutrient levels in staple crops can help prevent and reduce micronutrient deficiencies in one trial in Mozambique, eating sweet potatoes biofortified with beta-carotene reduced the incidence of vitamin A deficiency in children by 24%.
This approach may have advantages over other health interventions such as providing foods fortified after processing or providing supplements. Although these approaches have proven successful when dealing with the urban poor, they tend to acquire access to effective markets and healthcare systems which often just do not exist in rural areas. Biofortification is also fairly cost-effective after an initial large research investment where seeds can be distributed, the ‘implementation costs (of growing biofortified foods) are nil or negligible’, as opposed to supplementation which is comparatively expensive and requires continued financing, which may be jeopardized by fluctuating political interest.
Research on this approach is being undertaken internationally, with major efforts ongoing in Brazil, China, and India. Biofortified foods may also be useful for increasing micronutrient uptake in high-income countries. An example of this trend would be research into grain with higher levels of selenium, which, amongst other benefits, helps prevent prostate cancer. Researchers at the University of Warwick have been looking for ways to boost the low selenium levels in British grains, and have been working to help develop a grain to be used in making bread biofortified with selenium.
Relation between Conventional and Genetic Modification Plant Breeding
Conventional Plant Breeding
Conventional plant breeding involves changing the genes of a plant so that a new and better variety is developed. New varieties of plants are bred to suit different climate conditions, improve taste or nutritional value, cope with disease or pests better, or use water or nutrients more efficiently for example. To conventionally breed a new plant variety, two closely related plants are ‘sexually crossed’. The aim is to combine the favourable traits from both parent plants and exclude their unwanted traits in a singular new and better plant variety.
However, the progeny of this first cross inherit a mix of genes from both parent plants and so both positive and negative traits may be inherited. Breeders have to look at all the progeny and select the ones with the most positive traits and the least negative traits. They then cross this selected progeny back to one of the original parent plants to try and transfer more of its positive traits into the following generation. This process called ‘back crossing’ takes place over several generations, which usually means several years, until the progeny has all the desirable traits and none of the negative ones of the original two parent plant.
For example, a wheat variety that produces high yields in one region may be susceptible to a new disease. Another wheat plant may have a very low yield but has resistance to the new disease. Breeders can cross and backcross these two parent wheat varieties and their progeny to combine the high-yielding qualities of that parent with the disease resistance of the other parent. Conventional plant breeding may also use ‘wider crosses’ that involve crossing species or even genera that are quite unrelated. These crosses cannot occur without help so sophisticated techniques are employed.
Genetic Modification (GM) Plant Breeding
Breeding using genetic modification (GM) also involves changing the genes of a plant so that a new and better variety is developed. It is done for the same reasons as conventional breeding. The key difference is that instead of randomly mixing genes, which occurs as a result of a sexual cross, a specific gene, which is associated with a desirable trait, is selected and inserted directly into the new plant variety. This can save time and reduce the chance of undesirable traits in the new plant variety. GM also allows breeders to use genes from unrelated plants and sometimes other organisms in a new variety. This means breeders can access and use a wider choice of genetic diversity to develop new plant varieties. This is possible because all genetic information is stored in DNA which is the same chemical in all organisms.
In Australia, GM insect-resistant cotton contains genes from a soil bacterium, Bacillus thuringiensis (Bt), that provide very specific protection for the cotton against cotton’s number one pest Helicoverpa caterpillars. Across cotton’s entire genetic diversity, it does not have any genes that give Helicoverpa resistance. Using the Bt genes provided GM cotton with unique inbuilt protection that has reduced pesticide use by about 80% in the Australian cotton industry.
Is GM a natural form of breeding?
For thousands of years, farmers altered the genes of their crops. By selecting plants with desirable traits like higher yields and tastier produce, farmers inadvertently excluded undesirable genes and included desirable genes in each new generation of crops. These days even conventional breeding employs techniques to cross plants that could not occur without human assistance.
For example, conventional breeding uses chemical and physical means to ‘mutate’ plant genes. These gene mutations may give the plant different and even desirable traits. Plant breeders can then select these desirable traits caused by the mutated gene to breed new plant varieties. Mutations also occur naturally and these are also used in breeding.
Conventional breeding also crosses different species of plants to create hybrids. Plant hybrids are common in agriculture and horticulture and home gardeners would be familiar with hybrid flowers and vegetables. Conventional breeding can also benefit from GM. For example, scientists may think a particular gene is responsible for a certain desirable trait. To confirm this they can develop a GM plant using the gene in question. If this GM plant displays the desirable trait then it is likely the gene is responsible for the trait.
Breeders can then go back to the original plant and start breeding to include the desirable gene using techniques like DNA markers that ‘flag’ the location of the gene making it easy for breeders to know if the gene is present or not in each new generation of plant. This method speeds up the breeding of new plant varieties. The unique power of GM, however, lies in its ability to incorporate novel genes into new plants to develop plants with properties that would not be achievable through conventional breeding. This may mean using genes from unrelated organisms such as in the case of insect-resistant GM cotton.
The evolution of plant breeding has been occurring for thousands of years and GM is the latest development. Our ancestors embraced new plant breeding techniques as they emerged and we are the benefactors with a large range of new and improved plant varieties now available to us. GM is one of a suite of breeding tools that future generations can use to help tackle environmental and human health challenges.
Steps of Developing Genetically Modified (GM) Plants
(i) Isolating gene of interest:
Identifying and isolating genes responsible for the desired trait.
(ii) Insertion of the desirable gene into a vector:
The desirable gene is inserted in a vector e.g., Ti plasmid derived from A. tumefaciens by using DNA recombinant technology. Another method is through particle bombardment method when subcellular-sized particles are accelerated to high velocity to carry DNA or RNA into living cells. The gene gun method is used on seedlings or tissue culture cells. Before injections, microscopic gold or tungsten particles are liberally coated with several hundreds of gene copies.
(iii) Plant Transformation:
The transformed plasmid with transgene is mixed with explants. The latter takes up desired genes and forms transgenic or genetically modified cells that are then grown via various tissue culture methods. After regeneration, verification, and confirmation of normal function of inserted genes, performances are tested and assessed concerning bio-safety, so that the genetically modified crops can be safely consumed.