Precision breeding has tailor-made new rice varieties will combat the double burden of malnutrition and a pesticide-free environment, says Professor Dr Apichart Vanavichit from the Rice Science Center in Thailand
The world population is projected to increase exponentially to nearly 10 billion people in the year 2050. We will not only need 56% more caloric but also high nutrient foods to feed the future population. Unfortunately, during the next 30 years, climate change will make the task more challenging. Increasing average air temperature and uneven precipitation will not only limit productivity and acreage of rice production, but also nutrient density in rice production in the tropics. The situation is even worse when the prevalence of NCD is rapidly increasing to become a global threat in modern-day and beyond. The cause could be the overconsumption of simple, processed carbohydrate foods in young and elderly populations.
To mitigate the future food shortage, genetic improvement must consider multiple goals to increase yield potential, resistance to biotic and abiotic stresses and nutritional quality. It is worth noting that Thailand is one of the world’s top rice exporters with a strong emphasis on premium rice. If these new varieties are well accepted by consumers and farmers, the country could play a critical role in ensuring the supply chain of high nutrient foods for the world.
Rice for well-being
Consuming high caloric foods over an optimum daily caloric intake is a major cause of obesity and NCD as a consequence. Rice for wellbeing combines functional properties of starch, dietary fibre, prebiotic, antioxidant, nutrients, and micronutrients that can lower the risks of NCDs. Whole grain, in particular, pigmented rice fits all categories of the rice for wellbeing. Dietary fibre-rich whole grain rice prolongs hunger, allowing consumers to optimise their dairy caloric intake more efficiently. Specific dietary fibres help control the glucose spike of meal intake, resulting in a low glycemic index (GI), and consequently, a low risk of obesity and Type 2 diabetes. Also, it provides essential nutrients to enrich microbiota in your gastrointestinal tract that helps in enhancing your immune system against infectious and non-infectious disease such as diarrhoea, irritable bowel syndrome (IBS), inflammable bowel disorder (IBD), and colon cancer, etc. Therefore, breeding for attractive whole grain rice is the most sensible goal of breeding rice for wellbeing.
Rice for wellbeing must be cultivated in eco-friendly practices such as organic, pesticide-free, low carbon/water footprints. However, current rice production technologies depend on high such production inputs like herbicides, inorganic fertilisers, and pesticides which leave toxic chemical and heavy metal residues such as Cd and As in rice grains. As such, rice for wellbeing must be equipped with multiple resistance to diseases and insect pests. We have developed a breeding platform to effectively integrate all genes (QTLs) controlling multiple resistance/tolerance to 2-weeks flash flooding (F), and multiple resistance to bacterial leaf blight (B), leaf/neck blast (B), and brown planthopper (B). Now, nine existing cultivated Thai rice cultivars were successfully improved with the FBBB, enabling farmers for pesticide-free cultivation and food safety products. The most notable example is the newly improved variety called the Thai Jasmine Rice Plus 4 which can readily withstand the biotic and abiotic stresses along with the Jasmine rice grain quality1.
Climate change affects efficient rice cultivation in the rice bowl of Asia, in particular, 70% of Thai rice is grown in the world’s largest rain-fed lowland paddy fields. Extreme heat wave and water stresses during the rice growing season affect seed set and grain quality. As rice pollination is very sensitive to heat and water stresses, we have now successfully improved the seed set of a popular and high yielding Thai rice cultivar called Pitsanulok2. The new version has significantly improved seed set and seed quality in temperatures above 40 0C.
Rice has very low water use efficiency due to its high transpiration cooling and its photosynthetic nature. By collaborative work with the team led by Professor Julie Gray at the University of Sheffield, we isolated low stomatal density mutants (LD) that can improve water-use efficiency (WUE) and maintain high biomass under long-term water stress conditions. Pink Plus 5 and new varieties are in the final stages to fix LD trait with low GI, antioxidants, and FBBB on a high yielding genetic background.
From Riceberry to Rainbow Rice
Whole grain pigmented rice has the richest source of antioxidants due to varieties of anthocyanin, flavonoids, carotenoids, and phenolic compounds in comparison with non-pigmented whole grain rice. Breeding new pigmented rice varieties for superb cooking quality and resistance to multiple biotic and abiotic stresses have been undertaken. Riceberry is a newly selected purple rice from a cross between the world-renowned white Jasmine and the purple JHN rice. Consumers recognise Riceberry by its distinctive appearance, nutritional value, and unique aroma. Riceberry is the most popular model of rice varieties for nutritional studies and social development projects in Thailand2-6. As the most successful whole grain rice variety, Riceberry rice disrupts our mindset about the true value of rice for wellbeing9.
Pigmented rice leaves also offer even greater nutritional benefits. Unlike starchy grains, rice leaves provides 10 to 50 times more bioavailability of minerals and micronutrients because the leaves are free of phytate, an important anionic binder found mostly in rice and cereal grains as well. Additionally, rice leaves contain a higher quantity and quality protein and amino acid similar to green vegetables. We successfully developed new non-GM rice varieties expressing distinctive complex anthocyanin and chlorophyll patterns on the whole leaf area namely Rainbow Rice. The outcome is the disruptive vision of rice plants expressing on leaves with varieties of colours from red, pink, purple, blue, orange, yellow and green stripes similar to a rainbow. The Rainbow Rice leaves have high potential as the richest sources of antioxidants, dietary fibres, micronutrients, and amino acid. Thus, producing innovative food from rice leaves could effectively enhance global food security as well as improve the livelihood of rice farmers who generally live in poverty and underserved, so it could generate an additional stream of income from their existing agricultural product and tourism.
Low glycemic index rice
Soft-texture rice is the most popular and highly competitive in the global market, particularly in the region of Asia. Five newly improved soft rice varieties are tailor-made not only for multiple resistance but also enhancing micronutrients (Zn and Fe) and dietary fibre. Soft and sticky rice varieties normally have a high GI, however. In order to lower its GI, the first step is to maintain the whole grain high dietary fibre of these soft rice varieties. The new cultivar, Sinlex, with soft-texture brown rice has a low GI as instant cooked rice. To develop low GI of white rice (GI 52-55), breeding to reduce starch digestibility by increasing resistant starch and dietary fibre have been genetically improved in the new varieties, Pink Plus 4 and now, Pink Plus 5. Product development from these new low GI rice can be used to lower the risks of obesity and Type 2 diabetes among consumer who prefers white rice and products8.
Center of Excellence
The Center of Excellence on Rice Precision Breeding for Food Security, Quality, and Nutrition, a collaborative platform between the Rice Science Center, Kasetsart University, and the National Center for Genetic Engineering and Biotechnology have ambitious goals to develop new rice varieties by using modern, non-GM, precision breeding technology to tailor-made new rice varieties.
1 Vanavichit A, Kamolsukyeunyong W, Siangliw M, Siangliw JL, Traprab S, Ruengphayak S, Chaichoompu E, Saensuk C, Phuvanartnarubal E, ToojindaT, and Tragoonrung S.2018.Thai Hom Mali Rice: Origin and Breeding for Subsistence Rainfed Lowland Rice System. Rice (2018) 11:20.
2 Daiponmak, W Theerakulpisut, P., Thanonkao, P., Vanavichit, A., Prathepha, P. 2010. Changes of anthocyanin cyanidin-3-glucoside content and antioxidant activity in Thai rice varieties under salinity stress 9. ScienceAsia 36 (4): 286-291.
3 Leardkamolkarn V, Thongthep W, Suttiarporn P, Kongkachuichai R, Wongpornchai S, Vanavichit A. 2011. Chemopreventive properties of the bran extracted from a newly-developed Thai rice: The Riceberry. Food Chem. 125 (3): 978-985.
4 Prangthip, P., Surasiang, R., Charoensiri, R., Leardkamolkarn, V., Komindr, S., Yamborisut, U., Vanavichit, A., Kongkachuichai, R. 2013. Amelioration of hyperglycemia, hyperlipidemia, oxidative stress and inflammation in steptozotocin-induced diabetic rats fed a high fat diet by riceberry supplement. Journal of Functional Foods. 5 (1):195-203.
5 Pitija, K., Nakornriab, M., Sriseadka, T., Vanavichit, A., Wongpornchai, S. 2013. Anthocyanin content and antioxidant capacity in bran extracts of some Thai black rice varieties International Journal of Food Science and Technology. 48 (2):300-308.
6 Kongkachuichai, R., Prangthip, P., Surasiang, R., Posuwan, J., Charoensiri, R., Kettawan, A., Vanavichit, A. 2013. Effect of Riceberry oil (deep purple oil; Oryza sativa Indica) supplementation on hyperglycemia and change in lipid profile in Streptozotocin (STZ)-induced diabetic rats fed a high fat diet. International Food Research Journal. 20 (2): 873-882.
7 Ruengphayak, S., Chaichumpoo, E., Phromphan, S., Kamolsukyunyong, W., Sukhaket, W., Phuvanartnarubal, E., Korinsak, S., Korinsak, S., Vanavichit, A. 2015. Pseudo-backcrossing design for rapidly pyramiding multiple traits into a preferential rice variety. Rice; 8:7 (Developmental history of the Low GI PinK+4).
8 Nounmusig, J., Kongkachuichai, R., Sirichakwal, P.P.,Yamborisut, U., Charoensiri, R. and Vanavichit, A. 2018. The effect of low and high glycemic index based rice varieties in test meals on postprandial blood glucose, insulin and incretin hormones response in prediabetic subjects. International Food Research Journal 25(2): 835-841. (In vivo GI testing of the Low GI PinK+4).
9 Vanavichit, A. 2020. Riceberry Rice: Thailand’s Antioxidant-packed Nutraceutical Superfood. https://researchoutreach.org/articles/
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