2.4.3. Target values for breeders

Converting the nutrient requirements into target values for breeders is not straight forward as many factors need to be considered (2.7.3. Target values for breeders, Figure 2.4). One of the key factors is the sub population for which the crop is being fortified. Different cultures, countries or population groups within cultures, i.e. children, elderly, woman, people with certain diseases, have different dietary habits and requirements. The crop selected to be biofortified should have an existing consumption pattern that can be identified for the chosen population. That is, if consumed by the whole population in abundance, a food can be effective in reducing deficiencies through biofortification. For example, Lesotho is a country in the south of Africa that has high incidence of vitamin A deficiency. However, introducing yellow cassava in Lesotho will not be an effective strategy to decrease vitamin A deficiency as cassava is not a major staple crop there.

Nutritionists, plant breeders and food technologists established breeding targets for nutrient by crop, based on food consumption in the target population, also taking into account nutrient losses in storage and processing as well as nutrient bioavailability (Hotz and McClafferty 2007). The breeding targets for biofortified crops are often developed to meet the dietary needs and consumption patterns of women and children, as they are the most vulnerable for malnutrition.

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Figure 2.4: Main factors that determine breeding targets for the nutritional value of a crop for a certain sub population. This can be a population defined by culture or health condition, e.g. genetic makeup of people with certain disease that require personalised nutrition.

The HarvestPlus[1] project can serve as a nice example of a project in which clear breeding target values for nutrient content in crops were defined. Taking into account baseline micronutrient content in each crop, HarvestPlus set the following targets for preschool children 4–6 years old and for non-pregnant, non-lactating women of reproductive age (List from : Bouis and Saltzman 2017):

• The total amount of iron in high-iron beans and high-iron pearl millet will provide approximately 60% of the Estimated Average Requirement (EAR). Before breeding for high iron cultivars (baseline), this was 30% of the EAR.

• Zinc in high-zinc wheat and high-zinc rice will provide 60–80% of the EAR. Before breeding for high zinc cultivars this was 40% of the EAR at baseline.

• Provitamin A, the precursor of vitamin A, will provide 50% of the vitamin A EAR in the case of yellow cassava and orange maize, and up to 100% in the case of orange sweet potato. This was 0% provitamin A at baseline.

[1] https://www.harvestplus.org

The breeding target is the sum of the baseline micronutrient content and additional micronutrient content required for each crop and micronutrient combination. In Table 2.4 an example is shown of the breeding targets used by Harvest Plus.

Table 2.4: Example of how the breeding targets for provitamin A, Iron and Zinc (ppm) are used by Harvest Plus for different crops (Bouis and Saltzman 2017).