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Zinc Biofortification in Rice (Oryza sativa L.)

Written By

Anjali Singh

Submitted: November 2nd, 2021Reviewed: March 9th, 2022Published: April 19th, 2022

DOI: 10.5772/intechopen.104440

Revisiting Plant BiostimulantsEdited by Vijay Meena

From the Edited Volume

Revisiting Plant Biostimulants [Working Title]

Dr. Vijay Singh Meena, Dr. Hanuman Prasad Parewa and Dr. Sunita Kumari Meena

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Rice is a major energy source and micronutrient for more than half of the world’s population, but it lacks enough zinc to meet human nutritional needs. In addition, climate change, especially rising carbon dioxide levels in the atmosphere, is reducing zinc levels in grains. Therefore, rice bio-enrichment has been identified as a major goal for increasing zinc levels in grains to alleviate global zinc deficiency. There is a wide range to accelerate the development of High Zn varieties by applying biotechnology tools such as gene gun method and advanced genomics technology Successful intake and consumption requires an effective rice value chain, quality control and promotion of Zn bio-enriched varieties. Low zinc uptake, transport, and grain load have been identified as major bottlenecks in rice zinc bio enrichment. Nevertheless, the environmental and genetic factors of grain zinc accumulation in rice have not been fully studied. This review critically examines important genetic, physiological, and environmental variables that affect zinc uptake, transport, and utilization in rice. It also studies the genetic diversity of rice germ plasms and provides new genetic tools for bio-enhancement of zinc.


  • rice
  • malnutrition
  • biofortification
  • zinc
  • biotechnology

1. Introduction

Biofortification is the process of increasing the nutrient content of a plant from seed to harvest. This is different from food fortification, which increases the nutritional value of edible crops during processing. Biofortification improves the nutritional value of crops during the plant’s growth stage by embedding micronutrient content in growing crops. Bioenhancement of crops can be achieved by breeding or genetic engineering. In India, this is only done by breeding. Iron, zinc, and vitamin A deficiencies are the focus of bioenhanced research. These are micronutrients that affect most people around the world. In India, pearl millet (iron), wheat (zinc), sorghum (zinc), rice (zinc), sage (iron) and lentils are the main products (iron and zinc). Currently, bio-enriched pearl millet, rice and wheat are available to Indian farmers.

Biofortification, on the other hand, avoids the other three options by focusing on the production of nutrient-rich crops that can be cultivated and propagated using current agricultural practices. Fortification requires the use of unnatural additives, but bio-fortification depends on the natural ability of the plant to produce and store nutrients. Agricultural bioenrichment, also known as bioenrichment, is the use of inorganic fertilizers to improve mineral element concentrations and/or mineral element mobility and soil solubility of edible plant parts. Agricultural bioenhancement is simple and inexpensive, but requires special attention to nutrient supply, application, and environmental impact. Biofortification is the process of improving plant species to increase the nutritional value of the ingested product. The following are some of the key approaches that can be taken with the Plant Breeding Initiative to increase the nutrient content of the foods produced. Rice breeding for higher grain Fe and Zn content, rice breeding for higher grain carotene content, rice breeding for higher grain folic acid content, plant transformation techniques, protoplast transformation, fine particles Transformation with a gun (or microscopic gun), transformation with Agrobacterium tumefaciens, identification and in vitro-transformation tissue selection, gene expression and regulation, protein expression, proteomics. For vitamins in the Fe, Zn, and B complexes, it is necessary to confirm the occurrence of variability among rice genotypes. Therefore, it is possible to select these materials within the breeding program. Simple selection of these superior genotypes in terms of nutritional value, albeit with traditional breeding techniques, may benefit the consumption of rice by the human population (Figure 1)[1].

Figure 1.

Transformation of plants via A. tumefaciens.


2. Benefits of biofortification

In India, a movement similar to the Green Revolution aimed to end hunger. The country is expanding its edible grain production and is now almost self-sufficient as a result of the Green Revolution. The government is implementing several programs and measures to ensure that the population is consuming enough calories. However, the current focus is on improving the nutrient content of the diet. Many people do not get enough nutrients from their food intake, even if they have “sufficient food.” The result is a problem called “hidden hunger.”


3. Zn Deficiency

Human health problems are caused by zinc deficiency. More than half of the world’s population suffers from zinc deficiency. Food fortification improves the trace element content of nutrients and improves nutrition and bioavailability of trace elements. Fortification has made progress in controlling micronutrient deficiencies, but new approaches are needed, especially in developing countries. The process of increasing the natural levels of biologically available nutrients in plants is called bioavailability. Bio-enriched crops are a cost-effective strategy for combating micronutrient deficiencies. Zinc deficiency in plants can be quickly addressed with a variety of effective fertilization techniques.

3.1 Zinc estimation

Seed samples were peeled and polished according to a standardized protocol for analyzing samples with XRF. Seeds were manually washed and peeled using a Harvest Plus-sponsored JLGJ4.5 non-ferrous huller (Jingjian Huayuan International Trade Co., Ltd., Jiangsu Sheng, China). The peeled brown rice was sieved to remove the broken rice grains, and the complete brown rice grains were cleaned with soft tissue paper. With the hands of a trained person, the sample was lightly rubbed on paper for 1 minute with the hands of a gloved person to ensure that non-rice particles were removed. Each brown rice sample was ground on a specially designed K710 non-ferrous rice mill (Krishi International India Ltd., Hyderabad, India) and the ratio of milled rice was calculated based on the weight of white rice to brown rice. Brown rice samples were polished for 90–120 seconds until the desired whiteness was reached, as white rice is the most common method of consumption. White rice was polished in the same way as brown rice. The time between polishing and washing has been reduced to prevent the bran particles from adhering to the polished grain. Using Energy Dispersive XRF (EDXRF) (OXFORD Instruments XSupreme 8000, Highwycombe Bucks, England), each sample of white rice or white rice (5 g) was analyzed on a Harvest Plus-funded IIRR. The fluorescence intensity of each sample was converted to zinc content (mg/kg) by scanning the sample using a pre-standardized method. Use the zinc concentration of brown rice and white rice [1].

Zinc is an important trace element for normal and healthy plant growth and reproduction. Zinc is classified as a micronutrient due to its low levels of 5100 mg kg1 in plant tissue. Iron, copper, zinc, manganese, cobalt, chromium, iodine and selenium are all important micronutrients in the food chain. Many plant enzymes, including functional, structural, and regulatory enzymes, rely on zinc for their activity. Zinc is also beneficial in plant glucose metabolism, sucrose and starch production, protein metabolism, membrane integrity, and auxin metabolism.

Zinc plays an important role not only in the development of the human immune system, but also in the cellular processes of all living organisms. The recommended daily zinc intake for adults is 15 mg. Zinc acts as a catalyst or structural component of various human and plant enzymes. Zinc is required for many essential enzymes such as RNA polymerase, superoxide dismutase, lactate dehydrogenase, alkaline phosphatase, aldolase, and phospholipase. Zinc deficiency can impair the development of embryos, fetuses, newborns and young children, impair the immune system and delay cell recovery. Zinc deficiency is said to be responsible for the prevalence and disability of children under the age of 5 in low-income countries. Zinc supplementation has been shown to reduce visible diarrhea and respiratory illness in humans. Inadequate intake of zinc in the human diet due to zinc deficiency. Zinc deficiency leads to dire conditions such as hair loss, memory loss, and weakness of the body’s muscle tissue that occur in humans. Studies show that adult men need 11 mg of zinc daily and girls need 9 mg. During pregnancy, women should take 1315 mg of zinc daily. 3 mg of zinc per day for babies aged 7 months to 3 years, 5 mg per day for 48-year-old children, 8 mg per day for 913-year-old children Zinc deficiency stores zinc in the shell Because of this, it is common in people who are given grain. Grains are processed into flour. Foods rich in zinc include beef, chicken, almonds, walnuts, oatmeal, yogurt, cheese and milk. The bioavailability of the zinc and iron elements is significantly reduced due to the high content of phytic acid, dietary fiber and tannins, especially in cereal group plants.

It is a term used to refer to the fortification of foods, which increases the content of foods, especially trace elements, thereby improving nutrition and the bioavailability of trace elements. Adding iodine to table salt or adding Fe, Zn, and folic acid to bread crumbs is an example of fortification. The stability of the additive is low, which is a disadvantage in these applications. For example, adding folic acid to rice makes it easier to melt at high temperatures, and cooking rice makes it completely melt. Another drawback is that chemicals can compromise the quality of foods that are mixed in the long term. For example, additives containing iron oxidize and decompose over time, degrading the taste. Applying zinc to soil and/or crop leaves is a rapid way to increase zinc content (Table 1). Despite the fact that applying zinc to crops can increase yields and trace element concentrations, many farmers around the world (especially poor countries) do not. In agricultural bio-enhancement (soil/foliar fertilization, etc.), lowering the phytic acid/zinc molar ratio by reducing the phytic acid content of the crop can increase human Zn absorption.

Rice (Oryza Sativa)Soil, Soil+FoliarÖzcan [2], Özcan et al. [3], Özcan [4], Phuphong et al. [5], Grija Veni et al. [6]

Table 1.

Different methods used for zinc biofortification in rice crops.

A plant’s ability to transport amino acids is critical. Both phloem and xylem are involved in amino acid translocation. As a result, amino acid translocation aids nitrogen recycling between roots and shoots and speeds up the plant’s translocation of immobile nutrients, such as Zn. Furthermore, foliar application of urea to zinc fertiliser increases zinc transport throughout plants. Zinc applications will be a separate approach in the soil application of zinc, taking into account the growth periods of the plants.

3.2 Zinc biofortified rice

Rice is the most important food crop in the world and is trusted by more than half of the world’s population. Asia produces and consumes more than 90% of the world’s rice. India is the second largest rice producer in the world, producing 112.76 million tonnes from 2017 to 2018. Deficiencies or accumulation of important amino acids, micronutrients and vitamins result from an imbalanced supply that alters human metabolism.

According to the World Health Organization, zinc deficiency is the fifth most common cause of illness in developing countries and the eleventh in the world. Globally, the prevalence of zinc deficiency in soil is estimated to be 20%. Zinc deficiency causes diarrhea and respiratory illness, killing 400,000 people worldwide each year. Zinc deficiency is also associated with poor growth, loss of appetite, skin lesions, taste bud disorders, delayed wound healing, hypogonadism, delayed sexual maturation, and impaired immune response. In India, zinc malnutrition causes 1.31 million disability-adjusted life years (DALYs) to be lost each year. Preliminary analysis of rice zinc bio-enhancements in India shows that of the 1.31 million DALYs lost, 0.142 and 456,000 DALYs under pessimistic and optimistic assumptions when zinc bio-enhanced rice is introduced. I found that I could save money. As a “public good of the world”, the International Rice Research Institute and the International Agricultural Research in the form of the Wheat and Corn Improvement Center merged to form the International Agricultural Research Council Group (CGIAR), first carried out and led. it was done. The “Green Revolution” of the 1960s succeeded in improving grain production through the development of high-yielding varieties (HYV). However, HYV grains contain less nutrients. In the case of rice, milling further reduces nutritional levels, namely iron and zinc. Following this, in 1991, CGIAR responded to concerns expressed by the global nutrition community about micronutrient deficiency as a global issue, creating “micronutrient-rich” staple foods under signs of bioenhancement. Started research on. The Harvest Plus Challenge Program was launched by CGIAR in 2003 as a global program aimed at producing bio-enhanced staple crops such as wheat, rice, corn and cassava through plant breeding. Bioenhancement of rice grains with iron and zinc began in 1992 and 1995, respectively.


4. Techniques of biofortification

The major techniques or methods by which crops can be biofortified are mentioned below.

  1. Agricultural practices: This involves using fertilizers to increase the amount of micronutrients in plants grown in soils that are deficient in those nutrients.

  2. Traditional plant breeding: This is to create sufficient genetic variation in crop plants using traditional breeding methods, for example, to achieve high content of B. micronutrients. It involves mating types over several generations to produce nutritious plants and other desirable traits. In India, bio-enriched plants are produced only using this technology.

  3. Genetic engineering/engineering: This involves adding DNA to the organism’s genome to create new or altered traits, such as traits. B. Disease resistance to be introduced (Figures 2 and 3).

Figure 2.

Managing zinc deficiency through agronomic approach.

Figure 3.

Managing zinc deficiency through Particle Gun method.

4.1 Technology efficacy of zinc biofortification in rice

The current zinc intake from common rice varieties was determined based on the per capita consumption of 220 grams of rice per day. Improved zinc intake from bio-enriched rice varieties was calculated assuming that India’s current rice consumption pattern is maintained and bio-enriched rice varieties are being adopted as a technology.

Zinc is a component that contains more than 300 enzymes to repair cell damage, maintain fertility, synthesize proteins, and boost immunity among many important functions in human health [7]. Symptoms of zinc deficiency, large or small, can cause stunting, eczema, hair loss, delayed sexual maturation, and mental illness. Sustainable supply of dietary supplements (fertilization) and bioenrichment requires urgent efforts to overcome micronutrient deficiencies. Provision of supplementation through zinc fertilization of rice can increase zinc levels in rice [8]. However, this method is less effective due to nutritional loss from runoff, leaching, and the evaporation process. Therefore, a new strategy to overcome malnutrition of micronutrient is by the mean of biofortification. Biofortification provides a costeffective and sustainable solution in tackling the lack of nutrients supply [9]. This method is one of the plant breeding strategies to increase the zinc content in rice while improving the nutrition capacity with relatively low cost. Breeding materials are conventionally formed (hybridization and selection) or nonconventional (another culture and gene transformation). High zinc levels rice produced by these, inexpensive cost, production can be consumed directly by the middle to lower community as a source of energy and sources of nutrients [10]. As a result of these findings, rice has a high micronutrient content. Rice with a high micronutrient content can help customers get more micronutrients and overcome micronutrient insufficiency.


5. Biofortification challenges

Some of the challenges faced in biofortification and introducing biofortified food grains as part of the daily diet in India are discussed below.

  • Due to the colour changes in the grain, people hesitate to accept biofortified food as in the case of golden rice.

  • Farmers also should adopt this on a large scale.

  • The initial costs also could be a barrier for people to implement.

Zinc deficiency is a serious problem in developing countries where white rice is the staple food. The creation of bio-enriched rice varieties in India was sought with the help of Harvest Plus, the Biotechnology Department, and the Indian Agricultural Research Council due to the high genetic diversity of white rice’s high zinc content. Through the All-India Collaborative Rice Improvement Project (AICRIP), the Indian Rice Research Institute (IIRR) has enabled the release of rice varieties and is supporting India’s rice bioenhancement program. Different sets of germ plasms from several national institutions have been characterized for zinc content in IIRR of brown rice using energy dispersive X-ray fluorescence spectroscopy. This indicates that the zinc range is 7.3–52.7 mg/kg. Assessment of zinc content in various wild germ plasm mapping populations, native varieties, and cultivars demonstrated the feasibility of favorable rebinding of high zinc and high yields. Nine genotypes from genetic resources and 344 strains from the mapping population showed zinc levels of _28 mg/kg in white rice, meeting the target zinc levels set by Harvest Plus. Through AICRIP biofortification trial constituted since 2013, 170 test entries were nominated by various national institutions until 2017, and four biofortified rice varieties were released. Only the test entry with target zinc content, yield, and quality parameters is promoted to the next year; thus, each test entry is evaluated for 3 years across 17 to 27 locations for their performance. Multilocation studies of two mapping populations and AICRIP biofortification trials indicated the zinc content to be highly influenced by environment. The bioavailability of a released biofortified rice variety, viz., DRR Dhan 45 was found to twice that of control IR64. The four released varieties generated through traditional breeding had technology efficacy ranging from 48 to 75 percent, with zinc consumption of 38 to 47 percent and 46 to 57 percent of the RDA for male and female, respectively. The results of germplasm characterization and population mapping for zinc content, as well as the construction of a national evaluation system for the release of biofortified rice varieties, have been reviewed in the context of the five biofortification programme criteria.


6. Conclusions

Bio-enrichment of zinc-enriched rice is an effective means of combating zinc malnutrition in rice-dominated developing countries. Some progress has been made in understanding the molecular basis of zinc accumulation. By developing bio-enriched rice varieties with high zinc content in white rice, with domestic and international funding in India, we are addressing zinc deficiency, especially in developing countries where rice is an important staple food. .. Plants are at the top of the food chain and produce large amounts of nutrients for consumption by other species. As a result, enhancing the uptake of minerals from the soil and increasing their mobility and bioavailability in the edible parts of plants benefits human and animal nutrition. In addition, future bioenhancement will be needed to fully understand the number of nutrients in soil and plant ecosystems. This is a potential means of significantly impacting the nutritional problems of human health and providing more nutrients to the world’s population.



I would first like to thank my supervisor, Assistant Professor Dr. O.P.Verma, whose expertise was invaluable in formulating the research questions and methodology. Your insightful feedback pushed me to sharpen my thinking and brought my work to a higher level. In addition, I would like to thank my parents and my husband for their wise counsel and sympathetic ear. You are always there for me, who provided stimulating discussions as well as happy distractions to rest my mind outside of my research.


Conflict of interest

No conflict of interest.


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Written By

Anjali Singh

Submitted: November 2nd, 2021Reviewed: March 9th, 2022Published: April 19th, 2022