Major staple crops are often deficient in some of the essential vitamins and minerals and, in many areas of the world, the basic diet does not provide them in sufficient quantities. Thus, malnutrition, with respect to micronutrients like vitamin A, iron and zinc, affects >40% of the world’s population. It is estimated that, of the approximately seven billion people in the world, 60-80% are Fe deficient, over 30% are Zn deficient, and certain social groups do not receive sufficient Ca and Mg in their diets. Biofortification, which is defined as enriching the nutritional properties of edible crops, can be achieved through the combination of agronomy and plant breeding. Among the tools available to plant breeders, induced mutation is highly efficient in altering the genetic constitution of plants. Breeders use radiation to increase the chance of selecting specific desired traits, such as improved nutritional quality.
Mutation breeding includes artificial induction of mutations through irradiation, efficient screening of large mutant populations, and advancing of selected lines to varieties. In comparison to other approaches that have been used for improvement of nutritional quality in crops, mutation breeding is accessible to all Member States, accepted by governments and consumers, and allows the improvement of local varieties that are usually not targeted by other biotechnology procedures.
This CRP aimed to exploit mutant collections in selected crops, integrate tools from genomics, provide new germplasm resources, and deliver solutions to Member States to facilitate breeding for improved nutritional quality of food crops. Both the resulting mutant germplasm resources and the techniques for screening constituted the main expected outputs. These outputs provide breeders with highly valuable breeding material for development of new elite varieties with desired nutritional quality and also with the technology needed to start an own mutation breeding programme aimed at improving nutritional quality.
Throughout the course of the project, new mutant germplasm collections from elite varieties of the target crops barley, sorghum, sweet potato, maize, wheat, tomato, potato, pepper, rice and soybean have been developed. One rice mutant variety (China) and two maize mutant inbred lines (Ukraine) with improved nutritional quality have been officially released. Products with health benefits from rice, wheat and barley mutant lines have been developed and commercialized in China and Peru (Fig. 1 and 2).
This CRP also contributed to an increased knowledge of the metabolic pathways and genes affecting phytate, carotenoids, tocopherol, flavonoids and resistant starch biosynthesis, documented by numerous scientific publications. Efficient phenotypic screening methods for resistant starch, increased carotenoids and increased tocopherols were developed or optimized. These include colorimetric assays for phosphate and phytate for barley and wheat flour and for starch composition in maize and wheat and a method for HPLC analysis of some carotenoids (lutein, zeaxanthin, lycopene, beta-carotene). Moreover, retrotransposon based marker systems were adapted for rapid and robust genotyping of mutant lines. Experts interested in starting a national mutation breeding programme on nutritional quality will benefit from using these screening and analytical techniques, which will facilitate the selection process.
Several sorghum mutants have also been developed (Fig. 3) during the course of this project. Some of them are characterized by suppression of kafirin proteins. These are main sorghum proteins that are identified with poor digestibility and also difficult to extract and modify in an industrial-scale process, thus limiting their use in foods. The suppression of kafirins was counteracted by increased synthesis and accumulation of albumins, globulins and other proteins, thus ensuring the overall improved nutritional value of the seeds.
Within the project more than ten methods for phenotypic screening and analysis of nutritional components were developed or optimized/adapted. The information resulting from this CRP so far was disseminated through outreach activities including farmer days, academic and public lectures, community, workshops, public exhibitions and 40 scientific publications.
Fourteen research institutions have participated in this project from 12 countries: Bulgaria, China, Denmark, Germany, Ghana, India, Kenya, Peru, South Africa, the United Kingdom, Ukraine, and the United States of America.
For more information, please see the CRP description:
https://www.iaea.org/projects/crp/d23028