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01 June 2023
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Black rice is packed with healthy metabolites and can be improved to suit agricultural needs.
Pigmented rice varieties have significant nutritional value and can undergo modifications to achieve shorter height and faster growth, according to a recently published study by an international team led by researchers of King Abdullah University of Science and Technology (KAUST) in Saudi Arabia.
The team sequenced the DNA of 51 plants belonging to three black and two red rice varieties, evaluated their genetic variations, and sorted them into four major varietal groups. They also analysed the metabolites and metal ions present in rice grains to identify the most nutritious rice varieties that could become more attractive for farmers.
The analyses revealed that several black rice varieties stand out for their nutritional value. They contain a wide range of metabolites, including antioxidants, carbohydrates, amino acids, lipids, peptides and vitamins. The researchers identified 625 metabolites with about 60% of them significantly more abundant in black than red rice. For example, the analyses revealed the presence of fagomine, a biomolecule that can improve blood glucose management and insulin resistance, which had not been previously identified in rice.
Among all types of rice, the black Indonesian rice, Cempo Ireng, takes the lead: it is the richest in iron and vitamin B2, and could fulfil the daily requirement of these essential elements. However, farmers have been hesitant to cultivate this species due to its extended life cycle, which is two months longer than white rice, and its elongated lax stem that renders it vulnerable to adverse weather conditions and bird attacks. To tackle these issues, the researchers used CRISPR technology to modify three genes in Cempo Ireng that influence flowering time and plant height. These experiments led to plants that reached maturity 27-32 days faster and were 8–16 cm shorter than their original Cempo Ireng counterpart.
“These methods and genomic analyses could be used to introduce multiple traits to pigmented rice and develop new rice varieties that cater to consumer demands for healthier food options. We suggest promoting the substitution of white rice, which may lack essential nutrients, with the more nourishing black rice in our daily dietary habits,” says Magdy M. Mahfouz, bioengineering professor at KAUST.
“This success in reducing the heading date and plant height of Cempo Ireng not only provides a roadmap for generating high-yield pigmented rice varieties, but also highlights the value of genomic breeding technologies for targeted improvement of agronomic traits,” says Guosheng Xiong of Nanjing Agricultural University in China, who was not involved in the study.
Sedeek, K. et al. Multi-omics resources for targeted agronomic improvement of pigmented rice. Nat. Food https://doi.org/10.1038/s43016-023-00742-9 (2023).