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New challenges for plant breeders

Biofortification: Plants instead of pills

Millions of cases of illness and death, especially in developing countries, are caused by a lack of micronutrients like vitamins and trace elements. For this reason, nutritional supplements and industrially fortified foods are distributed in many developing and emerging nations. Now scientists are working on ways of fortifying the most important food crops with e.g. provitamin A, zinc and iron. Some of the methods used involve genetic engineering.

Golden Rice

Golden Rice: The grains contain beta carotene, also known as provitamin A because it is the most important of the substances converted into vitamin A. This turns the rice grains a yellow or orange colour. Photo: International Rice Research Institute (IRRI)

Cassava

Manioc, or cassava, is the most important staple crop in some parts of Africa. Genetic engineering methods are being used to fortify the edible roots with provitamin A, vitamin E, iron and zinc. Photo: cassava.ethz.ch

Sorghum bicolor

Sorghum fortified with micronutrients is due to be available as seed for farmers in 2017/18. Photo: Display garden of the Max Planck Institute for Plant Breeding Research, Cologne

Banana

Australian and African scientists are developing bananas fortified with micronutrients. Photo: Manfred Schütze, pixelio.de

Widespread deficiency symptoms and their consequences

Vitamin A defiency in children

Vitamin A deficiency: increased susceptibility to infection, blindness. According to WHO estimates, around 127 million children of pre-school age are suffering from vitamin A deficiency worldwide. Up to 500,000 go blind every year, and around half of them die within a year of going blind.

Iron deficiency: Anaemia in children

Iron deficiency: anaemia; mental development and learning difficulties, physical development and functional disorders. The WHO estimates that one in two pregnant women in developing countries and one in two children of pre-school age are affected by iron deficiency.

Zinc defiency: Impaired growth in children

Zinc deficiency: growth delays and higher susceptibility to infection among children, leading to higher child mortality rates.

Hunger does not only mean an insufficient calorie intake. In many parts of the world, especially in developing countries, people are suffering from serious health problems caused by a lack of micronutrients. This has also been called ‘silent hunger’.

Micronutrients are substances that the human body needs but cannot produce itself. These include vitamins, trace elements and amino acids. In order to obtain enough micronutrients, one needs a balanced diet, but this is something many people in developing countries cannot afford. Their diets are usually based on one staple crop, such as rice in Asia or cassava in parts of Africa. People usually eat the plant’s storage organs, which mostly contain starch. The consequences of this kind of unbalanced diet include growth and development disorders, increased susceptibility to infection and therefore higher mortality rates, or – in the case of vitamin A deficiency – blindness.

In the last few decades, many developing countries have distributed industrially fortified foods and food supplements containing important micronutrients. Despite some considerable successes, there have been, and still are, a number of problems with them. It is, for instance, often difficult to transport the products to remote rural areas, or to convince those affected that they really should take these foods and supplements regularly. The products also have to be produced and distributed constantly, at a considerable cost. Since the 1990s, scientists have been working on ways of fortifying local food crops with micronutrients in order to address these problems.

Fortified foods and supplements cannot and should not replace a balanced, varied diet. Nevertheless, organisations like the WHO and FAO are placing their hopes in these measures, because the problem of poverty, which means that lots of people are too poor to afford a balanced diet, is unlikely to be resolved even in the medium term.

Biofortification using conventional plant-breeding methods

In 2004, the Consultative Group for International Agricultural Research (CGIAR) launched HarvestPlus, a programme that now involves over 200 scientists at various research institutions worldwide. They are using conventional plant-breeding methods to fortify beans and pearl millet with iron, rice and wheat with zinc, and maize, sweet potatoes and cassava with provitamin A. The scientists are using varieties that are cultivated and consumed in developing countries. The world’s first biologically fortified crop plant to be marketed and consumed was developed within the HarvestPlus programme. It is an African sweet potato variety fortified with provitamin A.

Biofortification using genetic engineering

There are four projects around the world using genetic engineering methods to fortify important staple food crops with micronutrients. They are currently being funded by the Grand Challenges in Global Health Initiative set up in 2003 by the Gates Foundation. All the plants will be made freely available to small farmers in developing countries with no licence fees.

Golden Rice

Golden Rice grains contain beta carotene, also known as provitamin A, which the human body can convert into vitamin A. The beta carotene colours the rice grains yellow or orange. Unmodified rice plants produce carotenoids in their leaves and grain husks, but not in the grains themselves.

The first Golden Rice was developed in the 1990s by an international team led by Ingo Potrykus (ETH Zurich) and Peter Beyer (University of Freiburg). Two genes were inserted into rice plants. The genes contained the information for two enzymes from the carotenoid synthesis pathway. One was isolated from a soil bacterium; the other from a daffodil. Although rice does possess genes for both enzymes itself, they are both disabled in the grains. During the development of Golden Rice 2, the gene from the daffodil was replaced with one from maize.

The grains of the first Golden Rice plants did not contain enough provitamin A in a normal serving to provide a significant proportion of the required daily allowance. An average serving of Golden Rice 2 can provide most of the required daily allowance for people whose diet consists largely of rice. In 2009, a nutritional study showed that the provitamin A from the rice grains can be completely absorbed by the human body, which means it is available for human nutrition.

Over the years, the project has received the support of a number of foundations and companies that have waived their claim to intellectual property rights and licence fees. At the moment, the newly inserted genes are being bred into locally adapted Asian rice varieties using conventional plant-breeding methods in a project led by the International Rice Research Institute. The first varieties are due to be placed on the market in 2013. At the same time, the Philippine Rice Research Institute is working on a type of Golden Rice that has bacterial and virus resistance as well. Since 2005, the Grand Challenges in Global Health Initiative has been financing the international ProVitaminRice Consortium led by Peter Beyer, which is working on ways of fortifying Golden Rice with iron, zinc, vitamin E and proteins as well.

BioCassava Plus

The aim of this project is to fortify the edible roots of the cassava (manioc) plant with provitamin A, vitamin E, iron and zinc, whilst at the same time increasing the protein content and reducing cyanide levels. Other aims of the project are increased storage life and resistance to the cassava mosaic virus.

So far, scientists have managed to fortify the cassava with the planned levels of provitamin A and vitamin E, but the zinc and iron levels are only half as high as those aimed for. They have also managed to develop cassava plants with no cyanide in their roots. This means that there is more nitrogen available in the roots for the production of amino acids, and the protein level is higher than in unmodified plants.

Most of the research work is being carried out at the Donald Danforth Plant Science Center in St. Louis (USA). However, many other scientists are also involved, including some from the state agricultural research institutes in Nigeria and Kenya and from ETH Zurich.

Africa Biofortified Sorghum

The aim of this project is to fortify sorghum with provitamin A, vitamin E, iron, zinc and amino acids. So far, it has been possible to fortify the plant with three important amino acids and to reduce the amount of the kafirin storage protein. The reduced kafirin level makes the sorghum easier to digest. It has also been possible to reduce the amount of phytic acid in the grains, which means that zinc and iron, of which sorghum does actually contain enough, can be absorbed better by the human body and used more easily. The vitamin E content has also been considerably increased.

Most of the research work is being carried out by African scientists and institutions. Pioneer Hi-Bred is involved as an industry partner. The first seeds are due to be made available to farmers in 2017 or 2018.

Bananas with higher levels of micronutrients

The aim of this project is to fortify bananas with provitamin A, vitamin E and iron. For this, promoters were isolated from genes that play an important role in the relevant metabolic pathways in bananas. They were first inserted into bananas in various combinations to achieve improved fortification of the micronutrients mentioned above. Plantains have now been successfully transformed as well. Among the scientists involved in this project are some from the University of Brisbane (Australia), the state agricultural research centres in Uganda and Tanzania and US company ProCell.

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