One strategy for improving human health and the nutrition of resource poor people is increasing the iron content of beans. But what are the challenges for plant breeders?
Biofortification – a good strategy
Biofortification is a good strategy to improve the nutrition of resource poor people for a number of reasons:
• people do not need to change their eating habits – beans are major part of diets in many parts of the world, although, of course, it would always be better if they ate a more varied diet;
• people also do not have to spend more on what they eat to get better nutrition, since improved nutritional beans are not more expensive;
• the strategy is, in theory, more sustainable: once the improved seed varieties are distributed to farmers they can keep growing and selling them, while food fortification initiatives require constant production and distribution of the improved foodstuff;
• biofortified seeds can potentially reach more farmers, for example those living in remote, sparsely populated areas with poor distribution networks, such as in villages not served by roads.
But there are also important difficulties to overcome. For beans, these include the following.
The content of not just iron, but iron in a form capable of being used by the human body, known as bioavailable iron, must be increased.
Developing biofortified beans requires increasing the iron content of bean varieties above 94 microgams per gram. Wild bean varieties can be important sources of genetic diversity. Furthermore the increased levels of bioavailable iron must be retained during processing and cooking.
The level of iron absorption inhibitors must be minimised.
Some studies, including Petry et al. (2012), have shown that iron bioavailability of biofortified beans is low in varieties with high contents of iron absorption inhibitors such as phytic acid and polyphenols. This is something important that must be borne in mind during plant breeding initiatives.
And, very importantly, the biofortified bean must look and taste right.
People are unforgiving about taste, especially for crops that are culturally important and part of their everyday diet. Therefore, the improved varieties must be tasty, cook as fast as non-biofortified varieties, and look right.
The improved bean must accumulate higher levels of bioavailable iron from the soil and be grown under conditions recommended for a specific area.
Simply measuring increased bioavailable iron in research plots may not provide a good indication of how the variety will perform on farmers’ fields. Since plants absorb iron from the soil, testing the accumulation of this nutrient in different soil types, and climatic and agronomic conditions is important to select improved varieties that perform reliably. Different varieties perform better in certain conditions. For example, climbing beans are more productive in hilly areas and hence preferred by many farmers in Rwanda, whereas bush beans are favoured in flat areas, such as in large parts of Uganda. Seed size, colour, and cooking time are also important characteristics.
The biofortified varieties must also be high-yielding, or yield at least as much as non-biofortified varieties, and show resistance to local pests and diseases and to environmental stresses. Since the importance of pathogens that cause diseases changes over time, plant breeding is a continuous process, and increased iron content must hence be incorporated in the collection of characteristics breeders select for. It is not a matter of releasing a biofortified variety just once only.
The biofortified bean variety must conform to local preferences and market requirements.
Improved bean varieties should sell as well or better than the varieties they replace. And this could mean good business, for smallholder farmers and maybe also for small-scale entrepreneurs with seed businesses.
This also means that the success of biofortification initiatives does not only depend on plant breeding efforts: farmers must be able to obtain improved planting materials and information on how to grow them. This requires a functioning agricultural extension and good distribution system for seeds and for good quality fertilisers and pesticides. In other words, a good bean does not introduce itself.
And once farmers get hold of the seeds and the information on how to best to farm them, they also rely on good links with markets for subsequently selling their produce.
An integrated approach
A successful biofortification campaign should be able to demonstrate that the micronutrient levels of the target populations improves when they eat the biofortified varieties. Information on how iron nutrition effects other aspects of nutrition, such as zinc, and health, such as the effect on malaria and TB, is also needed. Improved nutrition goes far beyond plant breeding, but plant breeding is a good start.
Claudia Canales Holzeis is a plant molecular biologist with a near-decade of experience in plant genetics research. She previously worked as Senior Project Officer for the International Service for the Acquisition of Agri-Biotech Applications (ISAAA), based in the Philippines. A graduate of the University of Reading in Environmental Biology, Claudia Canales gained a DPhil. in Plant Genetics at Oxford.