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Developing rice (Oryza sativa) varieties high in iron (Fe) and zinc (Zn) content is a veritable approach for reversing the increasing trend of micronutrient deficiency affecting sub-Saharan Africa (SSA) countries, including Nigeria. The lack of empirical data on the amount of iron and zinc in rice grains of cultivated varieties hinders breeders’ ability to design effective breeding programs to develop crops rich in vital micronutrients to combat hidden hunger affecting human populations. The objective of this study was to screen available rice germplasms in Nigeria and determine their innate iron and zinc contents as a stepping stone to rice grain quality improvement. This study, therefore, screened sixty-one rice germplasms (48 improved varieties and 13 landraces) for Fe and Zn content. The experiment was carried out in March 2021 at the National Cereals Research Institute (NCRI), Badeggi, Niger State. Samples were prepared and digested, while iron and zinc concentrations were determined with the aid of an Atomic Absorption Spectrometry machine (iCE 300 AA02134104 v1.30). Observations recorded varied significantly for iron and zinc among the various genotypes examined. Many cultivated varieties commonly grown by the farmers exhibited abysmal low Fe and Zn concentrations (FARO-44 (Fe: 4.03, Zn: 4.26), FARO-52 (Fe: 3.43, Zn: 5.09) and FARO-67 (Fe: 3.73, Zn: 4.79). On the other hand, FARO 27 and NGB 00782, with outstanding Fe content of 16.69 mgkg−1, were good sources of Fe, whereas NGB 00791 (16.73 mgkg−1) appeared to be best for Zn. Considering genotypes that combined high content of both Fe and Zn, FARO-16 (Fe: 10.46, Zn: 15.32) and FARO-66 were most suitable for selection as donor parents.

Introduction

Rice (Oryza sativa L.) serves as a staple food that provides primary calories for more than 3.5 billion people across the world [1]. Though it is highly consumed globally, rice contains a limited amount of vital elements like iron and zinc that a man needs every day for optimal performance of his body system [2].

Iron is a vital constituent of blood, whereas zinc serves as a major co-factor for many important enzymes that stimulate good health in human beings [3]. In order to promote good health, 3 g–4 g and 1.5 g–2.5 g of Fe and Zn, respectively, must be found in the body of an average adult [4].

Zinc, being a vital stimulator of many enzymes, including regulatory proteins, also offers valuable tasks in the expression of several genes and the synthesis of DNA and RNA [5]. Most often, zinc deficiency usually mimics anemia caused by Fe deficiency in the human body because zinc is believed to have an influence on the absorption of iron in the intestines [6]. Researchers have also reported a high rate of child mortality globally because of inadequate intake of Fe and Zn [7].

According to research findings of Karen et al. [4], meat and cereal crops have been identified as the main sources where Fe and Zn are obtained by human beings for their daily needs. The bioavailability of Fe and Zn, therefore, will help the teaming rice consumers, especially in vulnerable sub-Saharan African countries, to combat the menace of lack of essential micronutrients in their diet [8]. Meanwhile, research has reported significant progress made over the years by the International Rice Research Institute (IRRI) in fortifying rice grain with vital micronutrients such as provitamin A (b-carotene), iron (Fe) and zinc (Zn) content through biofortification [9]. However, adoption and adaptation of most of these research findings is low across the various vulnerable African countries. The aim of this research, therefore, is to determine the variability of Fe and Zn contents among the available rice genotypes in Nigeria for selection purposes. This is to enable breeders to obtain useful information to design appropriate improvement programs to enhance the grain quality of major rice genotypes in Nigeria.

Materials and Methods

Sourcing of Germplasms

Sixty-one rice germplasms used for this research were sourced from different locations, which include National Cereal Research Institute, Badeggi, Niger State, National Center for Genetic Resources and Biotechnology, Ibadan, Oyo State, National Agricultural Seed Council Abuja, including from various lead farmers major rice producing states like Nasarawa and Taraba. They are:

• FARO-4, FARO-15, FARO-16, FARO-17, FARO-19, FARO-20, FARO-21, FARO-22, FARO-24, FARO-27, FARO-31, FARO-32, FARO-33, FARO-34, FARO-37, FARO-38, FARO-41, FARO-44, FARO-45, FARO-49, FARO-51, FARO-52, FARO-56, FARO-57, FARO-58, FARO-61, FARO-62, FARO-63, FARO-64, FARO-65, FARO-66, FARO-67, NCRO-48, NGB-00773, NGB-00775, NGB-00777, NGB-00778, NGB-00779, NGB-00781, NGB-00782, NGB-00783, NGB-00784, NGB-00786, NGB-00789, NGB-00791, NGB-00794, NGB-00827, NGB-00887, JASMIE, ATIME-EJU, GORKOCHA, MAI-ALURI, TUDU GAMBO, CHINA KARGO, D-BURI, N/ ALASKA, JANKARA, ALOGANI, YAR’ ADIZA, YAR’MAS, CD.

Screening of Grains for Micronutrient

All rice samples were screened in the biotech laboratory of the NCRI in March 2020. The screening started with sample preparation, digestion, and reading of the elements with an Atomic Absorption Spectrometry machine (iCE 300 AA02134104 v1.30).

Procedure for Samples Preparation

This involves cleaning 10 g of each sample by sieving with appropriate sieve material and dehusking with the help of a simple hand dehusker. Samples were then ground with Thomas Willey milling machine (Model ED-5) to become smooth powder.

Digestion of Samples

All samples were digested according to the procedure below:

Samples were digested in 250 cm3 glass conical flask covered with glass. 1 g of the already prepared sample was digested in 20 cm3 of Nitric Acid (HNO3) on a hotplate at a temperature of 110 °C for three hours. After evaporation to near dryness, the sample was diluted with 20 cm of 2% (v/v with H2O) nitric acid and transferred into 50 cm3 volumetric flask after filtering through Whatman no. 42 filter paper and diluted to 100 cm3 with deionized water [10]. The filtrates were separately analyzed using iCE 300 AA02134104 v1.30 Thermo Scientific Atomic Absorption Specrophotometer (AAS).

According to a report [11], the concentration (C) is calculated in mgkg−1 as:

C = ( X Y ) × V × 1000 / W × 1000

where

C – concentration/content of item

X – concentration of Sample

Y – concentration of blank

V – volume of flask used.

W weight of sample

Results

Biofortification is a technique for crop improvement through conventional breeding, which starts with the collection and screening of several germplasm. This will enable breeders to identify and select promising lines with desirable characteristics. Accordingly, Table I presented the record obtained for iron content and revealed wide variability between the different germplasms, with Fe content ranging between 0.07 mgkg−1 and 16.69 mgkg−1. Two varieties (FARO-27 and NGB 00782) recorded the highest value of 16.69 mgkg−1 each. Next to the topmost value was 15.48 mgkg−1 obtained in FARO-19 and NGB-00777. The next genotypes were FARO-20, FARO-31, and NGB 00779 with 15.18 mgkg−1. JASMIE followed next, recording 15.2 mgkg−1. Varieties FARO-38, NGB-00794, and ALOGANI (landrace) recorded (14.88 mgkg−1).

S/NO GENOTYP Fe (mg/kg) SD QLTVE ASMT S/NO GENOTYP Fe (mg/kg) SD QLTVE ASMT
1 FARO 4 4.34 ±0.0001 Low 32 FARO 67 3.73 ±0.0001 Low
2 FARO 15 0.99 ±0.015 Low 33 NCRO 48 3.73 ±0.002 Low
3 FARO 16 10.46 ±0.0007 High 34 NGB 00773 10.46 ±0.0008 High
4 FARO 17 4.03 ±0.0037 Low 35 NGB 00775 15.48 ±0.0003 High
5 FARO 19 15.48 ±0.0001 High 36 NGB 00777 4.34 ±0.0003 Low
6 FARO 20 15.18 ±0.0002 High 37 NGB 00778 3.73 ±0.0007 Low
7 FARO 21 14.88 ±0.0004 High 38 NGB 00779 15.18 ±0.0004 High
8 FARO 22 10.43 ±0.0008 High 39 NGB 00781 0.67 ±0.0204 Low
9 FARO 24 4.33 ±0.0002 Low 40 NGB 00782 16.69 ±0.0003 High
10 FARO 27 16.69 ±0.001 High 41 NGB 00783 1.89 ±0.0132 Low
11 FARO 31 15.18 ±0.0002 High 42 NGB 00784 3.73 ±0.0000 Low
12 FARO 32 2.2 ±0.0125 Low 43 NGB 00786 10.54 ±0.002 High
13 FARO 33 10.46 ±0.0009 High 44 NGB 00789 10.49 ±0.0004 High
14 FARO 34 3.73 ±0.0002 Low 45 NGB 00791 10.41 ±0.0003 High
15 FARO 37 3.43 ±0.0001 Low 46 NGB 00794 14.88 ±0.0007 High
16 FARO 38 14.88 ±0.0005 High 47 NGB 00827 10.6 ±0.0002 High
17 FARO 41 3.73 ±0.0026 Low 48 NGB 00887 3.73 ±0.0006 Low
18 FARO 44 4.03 ±0.0001 Low 49 THAI JASMIE 15.2 ±0.0005 High
19 FARO 45 0.07 ±0.0206 Low 50 ATIME-EJU 10.49 ±0.0003 High
20 FARO 49 10.59 ±0.0011 High 51 GORKOCHA 2.51 ±0.0093 Low
21 FARO 51 10.6 ±0.0005 High 52 MAI-ALURI 10.49 ±0.0005 High
22 FARO 52 3.43 ±0.0002 Low 53 TUDUGAMBO 10.49 ±0.0007 High
23 FARO 56 3.12 ±0.0044 Low 54 CARGO 4.34 ±0.0004 Low
24 FARO 57 4.34 ±0.0002 Low 55 DOGO-BURI 10.49 ±0.0006 High
25 FARO 58 2.21 ±0.0088 Low 56 ALASKA 3.73 ±0.0006 Low
26 FARO 61 4.03 ±0.0004 Low 57 JANKARA 10.41 ±0.0008 High
27 FARO 62 3.72 ±0.0046 Medium 58 ALOGANI 14.88 ±0.0003 High
28 FARO 63 10.44 ±0.0006 High 59 YAR’ ADIZA 4.03 ±0.0005 Low
29 FARO 64 2.51 ±0.009 Low 60 YAR’ MAS 3.11 ±0.0081 Low
30 FARO 65 10.62 ±0.0004 High 61 T/CD 4.03 ±0.0006 Low
31 FARO 66 10.54 ±0.0005 High
Table I. Grain Iron (Fe) of Sixty-One Rice Germplasms

Other genotypes with Fe content ranging from 10.0–11.0 mgkg−1 include FARO-65 (10.62 mgkg−1), while FARO-51 and NGB-00287 had 10.60 mgkg−1 each. FARO-49 contained 10.59, FARO-66 and NGB-00786 had 10.54 each. The next after that include ATIME-EJU, MAI-ALURI, TUDU GAMBO and BURI containing 10.49 mgkg−1 each. While FARO-16, FARO-33 and NGB 00773 contained 10.46 mgkg−1, FARO-63 and FARO-22 contained 10.44 and 10.43 respectively. Both NGB-00791 and JANKARA had 10.41 mgkg−1, while all other genotypes, including the commonly grown commercial varieties, contained abysmal low Fe content, which is less than 5.0 mgkg−1.

Similarly, the records, as shown in Table II, expressed variations in zinc contents of between 3.76 and 16.73 (mgkg−1) among the various rice genotypes investigated. Genotype NGB-00791 recorded the highest Zn content of 16.73 mgkg−1, while FARO-49 with 15.39 mgkg−1 came next. This was followed by MAI-ALURI (a landrace) with 15.46 mgkg−1, while FARO-49 and TUDU GAMBO had 15.39 mgkg−1 each. Both FARO-16 and NGB-00773 came next with 15.32 mgkg−1 and 15.31 mgkg−1 respectively. FARO-33 and FARO-66 obtained 15.25 mgkg−1 and 15.10 mgkg−1, respectively, while FARO-51 and NGB-00827 recorded 15.02 mgkg−1 each. NGB-00789 and BURI had 14.88 mgkg−1 each, followed by FARO-65 and NGB-00786 with 14.81 mgkg−1 each. FARO-22 and JANKARA obtained 14.53 mgkg−1 and 13.87 mgkg−1, respectively. All other genotypes recorded very low amounts of Zn below 6.0 mgkg−1, with FARO-44 and FARO-67 containing 4.61 mgkg−1 and 4.79 mgkg−1, respectively.

S/NO GENOTYP Zn (mg/kg) SD QLTVE ASMT S/NO GENOTYP Zn (mg/kg) SD QLTVE ASMT
1 FARO 4 4.19 0.004 Low 32 FARO 67 4.79 0.0059 Low
2 FARO 15 5.13 0.0005 Low 33 NCRO 48 4.59 0.0036 Low
3 FARO 16 15.32 0.003 High 34 NGB 00773 15.31 0.0047 High
4 FARO 17 4.59 0.0025 Low 35 NGB 00775 4.23 0.0047 Low
5 FARO 19 4.39 0.0045 Low 36 NGB 00777 4.26 0.0033 Low
6 FARO 20 5.2 0.0022 Low 37 NGB 00778 5.23 0.0018 Low
7 FARO 21 4.92 0.0044 Low 38 NGB 00779 4.97 0.003 Low
8 FARO 22 14.53 0.003 High 39 NGB 00781 4.67 0.0034 Low
9 FARO 24 4.56 0.0048 Low 40 NGB 00782 4.22 0.0014 Low
10 FARO 27 3.86 0.0019 Low 41 NGB 00783 4.39 0.004 Low
11 FARO 31 5.13 0.0016 Low 42 NGB 00784 5.27 0.0036 Low
12 FARO 32 4.19 0.003 Low 43 NGB 00786 14.81 0.0056 High
13 FARO 33 15.25 0.0024 High 44 NGB 00789 14.88 0.0042 High
14 FARO 34 5.25 0.0015 Low 45 NGB 00791 16.73 0.0032 High
15 FARO 37 5.2 0.0005 Low 46 NGB 00794 4.95 0.001 Low
16 FARO 38 5.17 0.0022 Low 47 NGB 00827 15.02 0.0054 High
17 FARO 41 4.61 0.0032 Low 48 NGB 00887 4.71 0.0048 Low
18 FARO 44 4.26 0.0048 Low 49 THAI JASMIE 5.23 0.0006 Low
19 FARO 45 4.09 0.003 Low 50 ATIME-EJU 15.31 0.0055 High
20 FARO 49 15.39 0.0022 High 51 GORKOCHA 4.06 0.0011 Low
21 FARO 51 15.02 0.0048 High 52 MAI-ALURI 15.46 0.0028 High
22 FARO 52 5.09 0.0056 Low 53 TUDUGAMBO 15.39 0.0029 High
23 FARO 56 3.86 0.0019 Low 54 CARGO 3.76 0.0002 Low
24 FARO 57 4.64 0.0043 Low 55 DOGO-BURI 14.88 0.0036 High
25 FARO 58 5.09 0.0036 Low 56 ALASKA 5.22 0.0047 Low
26 FARO 61 4.66 0.0049 Low 57 JANKARA 13.87 0.0031 High
27 FARO 62 3.96 0.002 Low 58 ALOGANI 4.93 0.0005 Low
28 FARO 63 15.32 0.0009 High 59 YAR’ ADIZA 4.74 0.0025 Low
29 FARO 64 3.98 0.0037 Low 60 YAR’ MAS 4.04 0.0014 Low
30 FARO 65 14.81 0.0041 High 61 T/CD 4.87 0.0028 Low
31 FARO 66 15.1 0.0034 High
Table II. Grain Zinc (Zn) of Sixty-One Rice Germplasms

Discussion

The results obtained from the screening revealed wide variability of iron and zinc content in the rice germplasms examined. This conforms the result by Nagarathna et al. [12], which expressed a wide genetic variability range of 8.4 mgkg−1–50 mgkg−1 Zn content in rice.

Many improved varieties and landraces contained a fair amount of Fe and Zn, but the study did not determine their location in the grain.

Most of the old varieties and landraces were found to contain appreciable Fe and Zn content. This was in agreement with a published report by Aladejana and Faluyi [13] that wild varieties of crops are reservoirs of desirable character useful for several genetic improvement research, including high yield. Varieties NGB 00782 and FARO 27 recorded the highest Fe (16.69 mgkg−1), while NGB 00791 had the highest Zn content of 16.73 mgkg−1.

Meanwhile, as with many of the improved varieties tested, the grains of FARO-44, FARO-52, and FARO-67 were very low in Fe and Zn. This could probably be attributed to the fact that yield and resistance to biotic and abiotic stresses are the prominent breeding targets in sub-Saharan Africa so as to cater to the food needs of the ever-increasing population in spite of nutritional quality. The study also revealed a positive correlation between the two elements, as varieties with low Fe are also low in zinc content. The above corroborates a report by Karen et al. [4] that Fe and Zn deficiency occur concurrently in the human body.

Conclusion and Recommendations

Since the majority of the resource-poor farm families grow FARO-44, FARO-52, and FARO-67 (due to their resilient and high-yielding characteristics) and rely on them as sources of their daily diet might be deficient in iron and zinc, varieties NGB 00782, FARO 27 and NGB 00791 could be exploited to improve the deficient commercial lines via hybridization to develop elite rice with high content of essential micronutrients like iron and zinc. Alternatively, both FARO 16 and FARO 66, which combined high concentrations of both Fe and Zn, could also be considered for selection as donor parents to develop varieties rich in Fe and Zn content for vulnerable populations. Field trials are also recommended on some landraces, such as TUDU GAMBO and MAIALURI that showed appreciable amounts of iron and zinc for genetic purity and further improvement research.

References

  1. Senguttuvel P, Padmavathi G, Jasmine C, Sanjeeva RD, Neeraja CN, Jaldhani V, et al. Rice biofortification: breeding and genomic approaches for genetic enhancement of grain zinc and iron contents. Front Plant Sci. 2023;14:1138408. doi: 10.3389/fpls.2023.1138408.
     Google Scholar
  2. Peramaiyan P, Craufurd P, Kumar V, Seelan LP, McDonald AJ, Balwinder-Singh KA, et al. Agronomic biofortification of Zinc in rice for diminishing malnutrition in South Asia. Sustainability. 2022;14:7747. doi: 10.3390/su14137747.
     Google Scholar
  3. Swamy BPM, Descalsota GIL, Nha CT, Amparado A, Inabangan-Asilo MA, Manito C. Identification of genomic regions associated with agronomic and biofortification traits in DH populations of rice. PLoS One. 2018;13(8):e0201756. doi: 10.1371/journal.pone.0201756.
     Google Scholar
  4. Karen HC, Lim LJ, Riddell CA, Nowson AOB, Ewa AS. Iron and Zinc nutrition in the economically-developed world: a review. Nutrients. 2013;5:3184–211.
     Google Scholar
  5. Garcia-Oliveira AL, Chander S, Ortiz R, Menkir A, Gedil M. Genetic basis and breeding perspectives of grain Iron and Zinc enrichment in cereals. Front Plant Sci. 2018;9:937, 1–13. doi: 10.3389/fpls.2018.00937.
     Google Scholar
  6. Graham RD, Knez M, Welch RM. How much nutritional iron deficiency in humans globally is due to an underlying zinc deficiency? Adv Agron. 2012;115:1–40. doi: 10.1016/B978-0-12-394276-0.00001-9.
     Google Scholar
  7. Black RE, Victora CG, Walker SP, Bhutta ZA, Christian P, de Onis M. Maternal and child under nutrition and overweight in low-income and middle-income countries. Lancet. 2013;382:427–51.
     Google Scholar
  8. Jena KK, Nissila EAJ. Genetic improvement of rice (Oryza sativa L.). In Genetic Improvement of Tropical Crops. Cham: Springer, 2017, pp. 111–27.
     Google Scholar
  9. Andersson MS, Saltzman A, Virk PS, Pfeiffer WH. Progress update: crop development of biofortified staple food crops under HarvestPlus. Africa J Food Agric, Nutr Dev. 2017;17:11905–35.
     Google Scholar
  10. Adedeji SA, Kakulu ES, Dauda SM. Analytical method for comparison of suitable wet digestion methods for heavy metal analysis in soil around a cement industry. Int J Res Sci Innov. 2020;7(6):41–7.
     Google Scholar
  11. Eddy NO, Ndibuke MO, Ndibuke EO. Heavy metals in sediment from cross river at Oron. Africa J Environ Pollut Health. 2004;3(5):21–6.
     Google Scholar
  12. Nagarathna TK, Shankar AG, Udayakumar M. Assessment of genetic variation in Zn acquisition and transport to seed in diversified germplasm lines of rice (Oryza sativa L.). J Agric Technol. 2010;6:171–8.
     Google Scholar
  13. Aladejana F, Faluyi JO. Agro-botanical characteristics of some West Africa indigenous species for a genome complex of the genus Oryza Linn. Int J Bot. 2007;3:229–39.
     Google Scholar