Plants grown as food crops possess a wide diversity of biologically active compounds which contribute to overall human health. The accessibility of food crops that are high in nutritional content is granted for those who live in the industrialised world.
However, this is not always the case for the rural poor who reside in developing countries. For such populations, a diet that is balanced in adequate levels of vitamins and minerals can be difficult to achieve and maintain.
All too often, a monotonous diet in which a single crop such as rice predominates is all that is on hand and affordable. Fortunately, due to recent developments in agricultural biotechnology, it is now possible to generate food crops which are nutritionally enhanced to improve the content and bioavailability of essential nutrients, such as iron and vitamin A.
Today, approximately 842 million people around the globe are undernourished, meaning that they do not get enough food to eat. Moreover, close to two billion of the world’s population suffers from ‘hidden hunger’, malnutrition caused not by too few calories, but by an inadequate intake of essential micronutrients in their daily diet.
People who suffer from malnutrition often consume meals which centre around a staple crop and as a result lack access to the wide variety of fruits and vegetables that are required for a healthy diet. As a consequence, close to one-third of childhood deaths under the age of five worldwide stem from undernutrition, and one child in four is stunted due to inadequate nutrition.
Over the next few decades, as the world population approaches ten billion, and with the advent of climate change, achieving food security will pose an even greater challenge. The vast majority of global population increase will most likely take place in the developing world, and global warming is expected to result in drought, flooding, and severe temperatures.
The development of plants which are nutritionally enhanced and resistant to abiotic stresses present a viable solution to these future challenges.
Traditionally, vitamins and minerals have been added to food crops through supplementation or biofortification practices. The provision of micronutrients in the form of supplements to malnourished populations has proven to be successful.
However, the extent of this success is unclear and such strategies are prone to fail in areas of scattered small populations or regions that become politically unstable. The use of supplementation programs may still fall short of the goals set in place by international health organisations.
Besides the expense, there is often too high a level of noncompliance among the population group that the supplementation program endeavors to help. Biofortification of crops can take place either by adding the appropriate mineral or inorganic compound to fertiliser, by conventional plant breeding, or through the use of biotechnology.
Although the application of fertilisers biofortified with micronutrients is the most simple of these methods, this practice can be confounded by the differences in mineral mobility and accumulation among plant species and different soil compositions in the specific geographical location of each crop, making success of this method highly variable. It is also necessary to apply the micronutrient regularly to the soil, therefore increasing both cost and labour.
The particular species of micronutrient ingested is also important. The organic species of a particular micronutrient can be more easily incorporated into tissue proteins such as red blood cells and skeletal muscle.
Organic species of micronutrients can also be stored more effectively by the body and micronutrient status retains for longer periods of time than inorganic micronutrients.
Another drawback is that it is not always possible to target the micronutrient into edible plant tissues and so this technique is only successful using certain plant species and mineral combinations.
Biofortification of food crops with minerals such as selenium, iodine and zinc have been achieved using this strategy. The design of conventional plant breeding programs to improve micronutrient content has also proven to be successful.
However, there are limitations with respect to the amount of variability in the plant gene pool and the time needed to generate cultivars with the desired traits.
Transgenic Crop Technology
As an alternative, the generation of micronutrient-dense biofortified crops through the use of biotechnology is at once more cost-effective, sustainable and realistic.
With transgenic crop technology, the genes of interest are inserted directly into the plant genome and the resulting recombinant proteins which are expressed may not be feasible under conventional plant breeding programs. Conventional breeding that can acquire and retain specific traits while not compromising others can be complex and comes with its own challenges.
In many occasions, it would be impossible to breed for a specific trait using conventional means, and the timescale and effort involved may be quite unrealistic.
While a certain amount of time and effort is initially involved in generating transgenic plants, the germplasm can be maintained at a low cost, in a timely manner, and without the need for nutrition-based organisational programs. Expected benefits of consumer traits have been estimated for some genetically modified (GM) crops as compared to their conventional counterparts.
Recently, a new line of biotechnology based on the principle of genome editing has come to the forefront. Genome editing focuses on nuclease-based forms of engineering such as the transcription activator like effector nucleases (TALENS) or the clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated (Cas) systems, and concerns the creation of precise incisions, mutations and substitutions in plant and other eukaryotic cells.
This technology will revolutionise the way we think about enhancing food crops to improve global nutritional status. It is less likely that new varieties of crops which harbour the small nucleotide modifications that are created by genome editing will be subjected to the same strict set of regulations as are currently held for transgenic crops.
As a result, genome editing may very well help plant biotechnologists avoid the same public controversy surrounding GMOs. Genome editing has been performed on crops such as barley, rice, tobacco, maize and arabidopsis, and is currently in a preliminary stage of development.
The generation of biotech food crops with improved attributes, such as increases in iron storage protein or greater levels of folate can provide sufficient levels of these and other much needed micronutrients that are frequently lacking in the diets of developing world.
Not only must these micronutrients be generated at high levels in plants, they must also be readily bioavailable, or absorbed and utilised by the body so that a consumer’s micronutrient status is improved even upon cooking or processing the food in the manner that a particular culture practices.
It is just as important that the biofortified crop be accepted by the community it is generated for and that it is readily adapted by farmers in significant enough numbers to improve a given community’s general nutritional health.
This can at times be problematic as some given populations remain wary of the use of genetically modified foods. The following section provides examples of biofortified food crops using biotechnology that are under development.
In spite of opposition groups, GM crops now account for more than 300 million acres worldwide and are grown by over 17 million farmers in more than 25 countries. The vast majority of the increase in farming of GM crops is in developing countries.
In 2012, the World Health Assembly (WHA) agreed on a set of global targets to hold the world accountable for reducing malnutrition. It is unlikely that these targets will be met within the timeframe set and new sustainable development goals are now being set up with the target date of 2030.
To achieve the goal of providing crops with additional health benefits on a global scale, much work is required and will involve interactions between many disciplines including plant breeders, molecular biologists, nutritionists and even social scientists.
It is not worthwhile to spend the effort generating a biofortified crop for a given population if they are knowledgeable, prepared and not already willing to accept the technology or any changes in appearance of the biofortified crop.
New crop varieties with enhanced nutritional qualities must be evaluated by clinical trials, and select populations who can benefit most from them must be educated so that they understand how these advantages can make a difference in their community’s overall health.
Research and development of nutritionally enhanced ‘orphan crops’ sorghum, millet, and pigeon pea, which are important to the world’s poor but overlooked by industrialized countries, must also be implemented. Cooperative efforts between governments, industry and non-profit organisations will truly eliminate hunger from the world’s rural poor.