By specifically targeting the nourishing tissues of the rice grain, the scientists – from the University of Geneva (UNIGE), in collaboration with teams at ETH Zurich and Taiwan’s National Chung Hsing University (NCHU) – succeeded in increasing its vitamin B1 content by three- to fourfold, without compromising agronomic yield.
‘‘Previous attempts at biofortification by other teams had succeeded in increasing the vitamin B1 content of the leaves and bran – the outer layer of rice grains – but not that of the ready-to-eat rice grain,” said first author Teresa Fitzpatrick, professor in the Department of Plant Sciences at the UNIGE Faculty of Science. “In our study, we specifically targeted the increase in vitamin B1 content in the endosperm.”
The results, published in Plant Biotechnology Journal, could help solve a major public health problem in regions where rice is the staple food.
Vitamin B1 in rice is lost during processing
Vitamin B1, also known as thiamine, is an essential micronutrient for human beings. Its deficiency is the cause of numerous diseases of the nervous and cardiovascular systems, such as beriberi.
Rice is the staple crop for half the world’s population, particularly in the tropical countries of Asia, South America, and Africa. Rice grains are low in vitamin B1, and processing steps such as polishing – removing the bran by grating the peripheral layers – reduce it even further, taking 90% with them. In populations where cereals such as rice are the main or sometimes the only food source, vitamin B1 deficiency is common, presenting a major public health problem.
Fitzpatrick’s team, in collaboration with researchers from ETH Zurich and Taiwan’s NCHU, focused on improving vitamin B1 content in the endosperm of rice – the nourishing tissue that makes up the bulk of the seed, and therefore of what is eaten.
They generated rice lines that express a gene that sequesters vitamin B1 in a controlled manner in the endosperm tissues. After growing in glasshouses, harvesting, and polishing the rice grains, they found that the vitamin B1 content was increased.
‘Promising’ experimental crops show potential of biofortification
The lines were then seeded in an experimental field in Taiwan and grown for several years. Characteristics such as plant height, number of stems per plant, grain weight, and fertility were comparable between both modified and unmodified plants.
However, the level of vitamin B1 in rice grains after the polishing stage was increased three- to fourfold in the modified lines. A 300 g bowl of rice from this crop provides one-third of an adult’s recommended daily intake of vitamin B1.
‘‘Most studies of this type are carried out with glasshouse-grown crops. The fact that we have been able to grow our lines under real field conditions, that the expression of the modified gene is stable over time without any of the agronomic characteristics being affected, is very promising,” said Wilhelm Gruissem, professor emeritus at ETH Zurich, and distinguished chair professor and Yushan fellow at NCHU.
