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INTRODUCTION

Rice (Oryza sativa L.) is a staple food in several countries, especially Asia. Rice grain contains carbohydrates, protein, fat, and fiber (Zhou et al., 2002) , and it is also a good source of phytochemicals (Chakuton et al., 2012; Ghasemzadeh et al., 2018;

Pereira-Caro et al., 2013). Currently, phytochemicals in rice grains receive more attention due to their antioxidant properties. Important phytochemicals in rice grain include tocopherols, dietary fibres, oryzanols, vitamins, phenolic compounds, and ferulic acids are beneficial to human health (Ghasemzadeh et al., 2018; Kim et al., 2014; Longvah & Prasad, 2020). Ferulic acid (FA) is a low molecular weight phenolic acid, a common component of the outer layers of cereal grains (Zupfer et al., 1998). The most abundant phenolic acid in rice is ferulic acid accounting for approximately 40-57% of total phenolic acid (Yu et al., 2016). It is found in dietary strand

fractions, and its free form has essential functions for protecting human health (Guo & Beta, 2013). Ferulic acid has a high antioxidant effect that will lessen the risk of diseases like cancer and diabetes (Boz, 2015;

Srinivasan et al., 2007; Zduńska et al., 2018).

At present, many genotypes of good rice have been developed for many important traits such as high aroma, resistance to environmental stresses, and valuable phytochemicals. In improving rice genotypes with good qualities, genetic variation of germplasm is an essential factor for success in breeding programs. Diverse germplasm sources with sufficient variations in target traits can increase production efficiency. Diversity of ferulic content is found in barley. The ferulic acid contents of 18 barleys range from 365 to 605 µg/g dry weight (Zupfer et al., 1998). In 53 local rice cultivars in Malaysia, the ferulic acid contents differed significantly among cultivars and ranged from 714.0 to 2,034.0 µg/g (Sing et al., ARTICLE INFO

Keywords:

DPPHGermplasm Landrace rice Phenol

Phytochemicals Article History:

Received: August 8, 2021 Accepted: December 15, 2021

*⁾ Corresponding author:

E-mail: chorkaew.an@kmitl.ac.th

ABSTRACT

Ferulic acid is a potent antioxidant in rice. The objective of this study was to evaluate the variations in ferulic acid and antioxidant capacity among landrace rice genotypes. The experiment is conducted under paddy field conditions in two locations. It uses a randomized complete block design with three replications, and the treatments consist of 24 landrace rice genotypes. Data are collected for yield and yield components, ferulic acid, and antioxidant capacity. Rice genotypes are significantly different for plant height, number of panicles per plant, number of seeds per panicle, 1,000 - seed weight and grain yield. Grain yields of 24 rice genotypes ranged from 1,476.9 to 4,348.1 kg/ha, and G24 is a good source for high grain yield. Variations in ferulic acid content and antioxidant capacity are found among genotypes. Ferulic acid contents range from 11.56 to 45.68 mg/100 g seed, and antioxidant capacity determined by the DPPH method ranged from 15.46 to 86.26%. G4 has the highest ferulic acid content and antioxidant capacity. These two genotypes are promising for parents in breeding programs targeting improved ferulic acid content, antioxidant capacity, and yield.

ISSN: 0126-0537Accredited First Grade by Ministry of Research, Technology and Higher Education of The Republic of Indonesia, Decree No: 30/E/KPT/2018

Cite this as: Aninbon, C., Srihanoo, C., & Phakamas, N. (2022). Genotypic variations in ferulic acid, antioxidant capacity and yield components of Thai landrace rice genotypes. AGRIVITA Journal of Agricultural Science, 44(1), 55–64. http://doi.org/10.17503/agrivita.v44i1.3084

Genotypic Variations in Ferulic Acid, Antioxidant Capacity and Yield Components of Thai Landrace Rice Genotypes

Chorkaew Aninbon^1*), Chayut Srihanoo²⁾ and Nittaya Phakamas¹⁾

1)Faculty of Agricultural Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand

2)Faculty of Natural Resources, Rajamangala University of Technology Isan, Phang Khon, Sakon Nakhon 47160, Thailand

2015). Moreover, Yu et al. (2016) reported that ferulic acid contents in Chinese rice ranged from 155.64 to 271.10 µg/g. However, 24 Thai landrace rice genotypes have not been evaluated for their content of ferulic acid and antioxidant capacity.

Therefore, the objective of this study was to assess the variation of ferulic acid and antioxidant capacity among 24 landrace rice genotypes. The results will be used in rice breeding programs.

MATERIALS AND METHODS Plant Materials and Experimental Design

Twenty-four genotypes of landrace rice were collected in Thailand for this study. For convenient presentation, these genotypes were designated as G1 to G24. All genotypes are photo-period sensitive, requiring a short day to induce flowering. These genotypes were evaluated in a randomized complete block design with three replications at two locations.

Location 1 (L1) was conducted in Nakhon Nayok province in the central region of Thailand (14°10’

N, 101°6’ E), and location 2 (L2) was carried out in Sakon Nakhon province in the Northeast of Thailand (17°19’ N, 103°49’ E) during July – December 2018.

The experiment was conducted in paddy fields under irrigated conditions in the primary growing season. Plot size was 3 × 5 m with a spacing of 20 cm between plants and 50 cm between rows. There were 72 plots totally for each location.

Cultural Practice

The seedlings of 25-day old were transplanted at the rate of 1 plant per hill in the same day on 13 July 2018 in both locations. Mixed chemical fertilizer formula 16-20-0 of N-P-K was applied at the 156.25 kg/ha rate at 15 days after transplanting (DAT). This research applied Nitrogen fertilizer in urea (46-0-0) at the rate of 62.50 kg/ha at the pre-heading stage.

Weed control and chemical pest control were done as necessary.

Data Collection Climate Data

Climate data of two locations, including rainfall (mm), relative humidity (%), and minimum and maximum air temperature, were recorded by the nearest weather stations throughout the experiment period.

Yield Components

Five plants in each subplot were randomly chosen at the flowering stage, and the data of plant

height were recorded. The same plants in each plot were also used to record the number of tillers per plant and the number of panicles per plant.

The seed yield of each subplot was measured at the harvest stage, and the seeds were sundried at approximately 13% moisture content and weighted for grain yield. One thousand seeds were randomly chosen and weighted to determine one thousand seed weight.

Ferulic Acid Determination by HPLC

Ferulic acid was determined according to the method suggested by Sawetavong et al.

(2010) with minor modification. Twenty-four × 50 g of each dehusked rice sample were grounded into a fine powder, and 24 × 1.0 g of the pieces were sub-sampled for ferulic acid analysis. The powdered samples were loaded into flasks, and 4 ml of methanol was added to each sample. The samples were mixed in a vortex mixer for 1 minute at room temperature, transferred to a water bath for 3 minutes at 30^οC, and then centrifuged for 5 minutes at 2,500 rpm. The rice extracts were collected and filtered through a 0.45 µm pore size syringe filter before injection into the C16 HPLC column. The mobile phase was methanol: acetic acid (99.5: 0.5 v/v). The flow rate was 1.2 ml/minute, and the UV detector was 326 nm.

DPPH Scavenging Activity

The DPPH radical scavenging activity of each extract was determined using the method Kaur et al. (2017) suggested with some modifications. Rice extract (0.1 ml) was added to 2.9 ml freshly prepared solution of 0.1 mmol/l methanolic solutions of DPPH. The control sample contained 1 ml methanol without extract plus the methanolic solution of DPPH (2.9 ml). After that, the sample was incubated for 30 minutes in the dark at room temperature. The absorbance at 517 nm was measured using a UV- visible spectrophotometer. The percent inhibition activity was calculated as formula 1).

Scavenging activity (%) = [(A control−A sample) / A control] × 100% ... 1) where A control is the absorbance of control samples and A sample is the absorbance of test samples read at 517 nm.

Data Analysis

Data were analyzed statistically according to a randomized complete block design using the SAS program. Duncan’s Multiple Rang Test (DMRT)

compared means at 0.05 and 0.01 probability levels.

Cluster analysis was done by STATISTICA 7 program.

RESULTS AND DISCUSSION Combined Analysis of Variance

The locations are significantly different for plant height, number of panicles per plant, number of seeds per panicle, 1000-seed weight, and ferulic acid content (Table 1). The interactions between location and genotype are significant for all traits.

Therefore, the data in each site are reported.

Climate Data

Climate data are different between locations (Fig. 1). Rain falls are 2,424.5 mm in L1 and 390.8 mm in L2. Relative humidity range from 64 to 95% in L1 and 57 to 94% in L2. Maximum temperatures (Tmax) were 23.4°C in L1 and 31.8°C in L2. Minimum temperatures (Tmin) were 17.6°C in L1 and 22°C in L2.

Yield Components

In Nakhon Nayok location (L1), the plant height of 24 landrace rice genotypes ranges from 127.73 to 174.83 cm. G20 has the highest plant height, whereas G3 is the lowest for this trait. The panicles per plant range from 7.66 to 15.50 panicles (Table 2). The highest number of panicles per plant is G24, followed by G4 and G20 with the vales of 15.50, 15.00, and 12.33 panicles per plant, respectively. The numbers of seeds per panicle range from 123.67 to 218.33 seeds. The genotype with the highest number of seeds per panicle is G12 (218.33 seeds per panicle), and the genotype with the lowest number of seeds per panicle is G13 (123.67 seeds per panicle). One thousand seed weights range from 21.80 to 33.40 g. Variation in grain yield was observed among 24 landrace rice genotypes grown in Nakhon Nayok province. Grain yields ranged from 1476.9 to 4313.9 kg/ha. G4 has the highest grain yield, followed by G24, and G15 has the lowest.

In Sakon Nakhon location (L2), plant heights varied from 91.16 to 133.41 cm. G7 has the highest plant height, followed by G20 and G4 with the values of 133.41, 127.25, and 170.41 cm, respectively (Table 3). The number of panicles per plant is highest in G24, with a value of 12.16 panicles per plant, and the lowest genotype for this trait is G10. The numbers of seeds per panicle range from 121.75 to 244.08.

The highest genotype for the number of seeds per panicle is G21, whereas the lowest genotype is G5.

One thousand seed weights of 24 rice genotypes range from 23.00 to 41.60 g. Grain yields ranged from

1,671.9 to 4,348.1 kg/ha. The highest genotype for grain yield in Sakon Nakhon location is G24, followed by G23 and G14, whereas the lowest genotype for grain yield was G5.

On average, the Nakhon Nayok location has taller plants and more panicles per plant than the Sakon Nakhon location. In contrast, the Sakon Nakhon location has more seeds per panicle, heavier seeds, and higher grain yield than the Nakhon Nayok location (Table 2, Table 3). The average grain yield in Sakon Nakhon location (2,899.5 kg/ha) is higher than in Nakhon Nayok location (2,659.1 kg/ha). The results are due to the higher rainfall in Nakhon Nayok province during the vegetative phase. This condition promotes the higher vegetative growth of rice in this location.

This study’s grain yields of landrace genotypes range from 1,476.9 to 4,348.1 kg/ha. In the previous research, two landrace rice varieties have grain yields in the range of this study in which Leum Pua and Hom Dong had grain yields of 1,880.5 and 2,376.1 kg/ha, respectively (Rodnuch et al., 2019). Dhakal et al. (2020) also find that grain yields of 30 landrace rice varieties in Nepal range from 1,630-3,260 kg/ha. The results in this study indicate that this germplasm has variation in grain yield, and G24 is the best variety for genetic resources of high grain yield because the grain yield of this variety is high in both locations.

Ferulic Acid Content

Landrace rice genotypes in both locations are significantly different for ferulic acid content (Table 4). In Nakhon Nayok location (L1), G4 has the highest ferulic acid content (41.10 mg/100 g seed) followed by G22 (38.43 mg/100 g seed) and G6 (34.76 mg/100 g seed), whereas G24 have the lowest ferulic acid content (11.56 mg/100 g seed). In Sakon Nakhon location (L2), G4 also has the highest ferulic acid content (45.68 mg/100 g seed) followed by G6 (39.23 mg/100 g seed) and G1 (31.23 mg/100 g seed), whereas G21 has the lowest ferulic acid content (12.39 mg/100 g seed).

Ferulic acid accounts for the highest level in bran fraction in grain and is vital for protecting human health. Yu et al. (2016) studied individual phenolic acids in 20 rice varieties in China, and they found that ferulic acid was most abundant in rice, comprising 40-57% of total phenolic acid. In this study, colored genotypes have higher ferulic acid content than white genotypes (G4 G22 G6 in L1 sand G4 G6 and G1 in L2).

Table 1. Mean squares from combined analysis of variance for plant height, number of panicles per plant (Pa./Plant), number of seed per panicle (Seed/Pa.), 1,000-seed weight (1,000 SW), grain yield, ferulic acid content and antioxidant capacity (DPPH) of 24 rice genotypes across the location.

Source df Plant height

(cm) Pa./

plant Seed/Pa. 1,000 SW (g) Grain yield (kg/ha)

Ferulic content (mg/ 100 g

seed)

DPPH (%) Location (L) 1 46519.3** 35.9* 2837.7* 19164.9** 43367.4^ns 132.56** 1.8^ns

L*REP 4 1163.9 45.3 372.4 0.2 93752.3 19.31 166.0

Genotypes

(G) 23 433.9** 13.9** 2475.3** 10.9** 46638.6** 342.29** 2437.4**

L*G 23 211.9** 6.3* 1727.8** 8.1** 27850.5** 32.83** 170.9**

Error 92 121.6 3.2 473.6 0.3 11715.5 5.81 16.5

Total 143

CV (%) 8.58 18.11 12.93 3.63 24.24 11.47 11.73

Remarks: ns, * and ** = non-significant, significant at P ≤ 0.05 and significant at P ≤ 0.01, respectively.

Fig. 1. Rainfall, relative humidity (mm), maximum temperature (Tmax) and minimum temperature (Tmin) during August – December 2018 of Nakhon Nayok and Sakon Nakhon provinces.

Table 2. Means for plant height, number of panicles per plant (Pa./Plant), number of seed per panicle (Seed/Pa.), 1,000-seed weight (1,000 SW) and grain yield of 24 landrace rice genotypes grown at Nakhon Nayok province.

No. Land race Plant height (cm) Pa./plant Seed/Pa. 1,000 SW (g) Grain yield (kg/ha) G1 Glam Fueang 143.33^bcd 11.56^b-e 148.33^d-i 28.23^b-e 2,896.7^bcd

G2 Ei Tia 152.50^a-d 8.50^de 199.33^ab 25.26^gh 2,599.9^bcd

G3 Mali Hom 127.73^d 9.33^cde 149.33^d-i 23.77ⁱ 1,916.3^d

G4 Glam Luem Phua 161.83^ab 15.00^ab 177.67^b-f 25.03^g-i 4,313.9^a G5 Nhiao Dang 2 153.83^a-d 9.16^cde 180.67^bcd 28.83^bc 2,879.1^bcd

G6 Mali Dum 137.83^bcd 8.00^e 136.00^ghi 28.33^b-d 1,766.1^d

G7 Mali Duang Doem 141.17^bcd 8.33^de 168.67^b-h 23.86ⁱ 2,006.4^d

G8 Nang Nual 156.50^a-c 11.16^b-e 150.67^c-i 25.43^gh 2,550.1^bcd

G9 Whan 2 154.17^a-d 9.66^cde 166.33^b-h 24.46^g-i 2,352.5^cd

G10 Mhag Hai 142.67^bcd 7.66^e 134.67^hi 33.40^a 2,059.3^d

G11 Lhueang Thong 151.33^a-d 9.66^cde 178.67^b-e 24.36^hi 2,602.7^bcd

G12 Ta Nan 146.50^bcd 9.83^cde 218.33^a 27.20^de 3,502.3^abc

G13 Ma Yom 131.67^cd 10.00^cde 123.67ⁱ 27.50^c-e 2,064.5^d

G14 Khaw Hom 152.17^a-d 10.83^cde 160.33^c-h 28.93^b 3,029.5^bcd G15 Hom Nual 141.50^bcd 9.66^cde 163.33^c-h 24.23^hi 1,476.9^d G16 Hom Nang Nual 1 140.17^bcd 12.83^abc 176.00^b-f 25.16^ghi 3,802.3^ab G17 Hom Nang Nual 2 146.17^bcd 10.66^cde 142.67^f-i 26.90^ef 2,775.4^bcd

G18 Nhiaw Ma Li 139.33^bcd 8.16^de 155.00^c-i 24.26^hi 1,851.3^d

G19 Hom Sa Ngiam 148.00^a-d 8.50^de 186.00^bc 27.13^de 2,626.4^bcd

G20 Tong Ma Ang 174.83^a 12.33^a-d 169.00^b-h 27.53^c-e 3,404.6^abc

G21 Khaw 141.67^bcd 11.50^b-e 173.00^b-f 25.80^fg 3,073.1^bcd

G22 Mali Nil Boran 142.33^bcd 10.16^cde 171.00^b-g 21.80^j 2,251.4^cd G23 Jaw Mali Dang 144.17^bcd 11.33^b-e 143.33^e-i 23.77ⁱ 2,309.9^cd G24 Siw Gliang 144.00^bcd 15.50^a 161.67^c-h 23.88ⁱ 3,709.0^ab

Max 174.83 15.50 218.33 33.40 4,313.9

Min 127.73 7.66 123.67 21.80 1,476.9

Average 146.47 10.39 163.90 26.04 2,659.1

Remarks: Means in the same column followed by the same letter were not significantly different at P ≤ 0.05 by DMRT.

Table 3. Plant height, number of panicles per plant (Pa./Plant), number of seed per panicle (Seed/Pa.), 1,000-seed weight (1,000 SW) and grain yield of 24 landrace rice genotypes grown at Sakon Nakhon province.

Genotypes Plant height (cm) Pa./plant Seed/Pa. 1000-seed weight (g) Grain yield (kg/ha)

G1 108.91^b-f 9.91^abc 148.33^f-j 33.90^c 2,934.4^a-e

G2 114.83^a-e 10.66^ab 205.17^a-d 25.16^jk 3,479.4^a-d

G3 92.33^e-f 10.50^abc 143.00^g-j 24.00^kl 2,623.8^b-e

G4 120.41^a-d 10.50^abc 178.00^c-i 25.80^ij 2,985.0^a-e

G5 96.00^ef 7.50^a-d 121.75^j 30.14^efg 1,671.9^e

G6 91.16^f 9.50^abc 155.75^e-j 32.70^dc 2,917.5^a-e

G7 133.41^a 11.25^ab 184.17^b-h 23.63^kl 2,969.4^a-e

G8 111.41^a-f 10.58^abc 134.17^ij 25.76^ij 2,183.8^cde

G9 111.66^a-f 10.00^abc 150.25^e-j 29.43^fg 2,630.5^b-e

G10 113.58^a-f 4.91^d 157.08^d-j 37.96^b 1,733.1^e

G11 119.91^a-d 9.41^a-d 186.25^b-g 24.55^jkl 2,582.5^b-e

G12 114.58^a-f 9.00^a-d 136.75^hij 30.83^ef 2,266.3^cde

G13 119.16^a-d 5.91^cd 195.67^b-f 29.51^fg 2,079.4^de

G14 98.33^def 10.28^abc 198.08^b-e 31.63^de 3,827.5^abc

G15 119.25^a-d 9.41^a-d 145.42^g-j 29.53^fg 2,429.4^b-e

G16 112.75^a-f 9.08^a-d 212.17^abc 25.77^ij 2,994.4^a-e

G17 122.00^ab 9.83^abc 162.75^d-j 27.40^hi 2,604.4^b-e

G18 111.00^a-f 9.25^a-d 153.83^e-j 41.30^a 3,514.3^a-d

G19 109.25^b-f 9.00^a-d 227.92^ab 30.25^efg 3,728.8^a-d

G20 127.25^ab 10.16^abc 180.17^b-i 31.06^ef 3,389.4^a-e

G21 100.08^c-f 7.25^bcd 244.08^a 28.70^gh 3,211.9^a-e

G22 103.16^c-f 9.25^a-d 181.83^b-i 23.00^l 2,352.5^cde

G23 99.91^c-f 10.08^abc 163.50^d-j 41.60^a 4,132.5^ab

G24 102.25^c-f 12.16^a 180.67^b-i 33.10^dc 4,348.1^a

Max 133.41 12.16 244.08 41.60 4,348.1

Min 91.16 4.91 121.75 23.00 1,671.9

Average 110.52 9.39 172.78 29.80 2,899.5

Remarks: Means in the same column followed by the same letter were not significantly different at P ≤ 0.05 by DMRT.

Table 4. Means for ferulic acid content (FA) and DPPH of 24 landrace rice genotypes grow in Nakhon Nayok province and Sakon Nakhon province.

Genotypes Pericarp color

Nakhon Nayok Sakon Nakhon

FA content

(mg/ 100 g seed) DPPH

(%) FA content

(mg/ 100 g seed) DPPH (%)

G1 Black 26.94^cd 37.40^c 31.23^c 36.23^cd

G2 White 16.28^f-i 24.66^d-f 17.37^f-i 31.16^d-g

G3 White 19.28^e-h 19.53^f 16.32^g-i 42.80^c

G4 Black 41.10^a 63.91^b 45.68^a 70.20^b

G5 Red 23.51^c-e 85. 39^a 17.74^f-i 84.17^a

G6 Black 34.76^b 68.28^b 39.23^b 68.13^b

G7 White 19.72^e-g 22.11^f 16.68^g-j 29.76^d-h

G8 White 15.27^ghi 22.13^f 17.42^f-i 32.60^c-f

G9 White 19.93^e-g 22.78^ef 15.62^h-k 27.90^d-j

G10 White 24.63^c-e 29.07^de 19.32^efg 34.06^cde

G11 White 16.40^f-i 20.83^f 14.88^i-l 25.13^d-k

G12 White 18.52^e-f 25.12^def 16.76^g-j 22.43^f-k

G13 White 27.63^cd 21.87^f 20.86^e 22.66^f-k

G14 White 13.48^hi 21.87^f 14.12^jkl 21.30^g-k

G15 White 28.42^c 25.35^def 21.84^e 23.02^e-k

G16 White 16.43^f-i 24.90^def 16.62^g-j 16.03^k

G17 White 14.32^ghi 21.94^f 13.07^kl 17.70^ijk

G18 White 19.90^efg 22.22^f 17.96^fg 29.70^d-h

G19 White 19.97^efg 29.96^d 15.29^h-l 16.93^jk

G20 White 22.29^d-f 29.91^d 25.64^d 28.00^d-j

G21 White 16.03^ghi 25.12^def 12.39^c 15.46^k

G22 Black 38.43^ab 64.41^b 21.87^e 28.36^d-i

G23 Red 22.38^d-f 82.94^a 21.12^ef 86.26^a

G24 White 11.56ⁱ 22.94^ef 13.18^kl 19.16^h-k

Max 41.10 85.39 45.68 86.26

Min 11.56 19.53 13.07 15.46

Average 21.97 34.78 20.09 34.55

Remarks: Means in the same column followed by the same letter were not significantly different at P ≤ 0.05 by DMRT.

A previous study shows that ferulic acid content is higher in pigmented rice than non- pigmented rice (Goufo & Trindade, 2014).

Chakuton et al. (2012) found that the 53 colored Thai rice genotypes showed the highest total phenolic content (TPC) than those non-colored.

Ghasemzadeh et al. (2018) also find that ferulic acid content is the highest in black rice, followed by red and brown rice, respectively. This study’s ferulic acid contents range from 11.56 to 45.68 mg/100 g seed. According to Boz (2015), ferulic content in cereals including brow rice was 42 mg/100 g seed, which was in the range of ferulic content in this study. Moreover, Zupfer et al. (1998) found that ferulic acid contents in 18 barleys ranged from 34.32 to 57.97 mg/100 g, which had a higher range than this study. Also, a similar result is found in 17 ryes plants (Andreasen et al., 2000). The G4 and G6 have high ferulic content in both locations. The results indicate that these genotypes can be used as parental lines in breeding programs for rice’s high ferulic content.

Antioxidant Capacity

Antioxidant capacity is measured by DPPH radical scavenging activity. The antioxidant capacity values are significantly different among rice genotypes in both locations (Table 1, Table 4). Sites are not considered other for antioxidant capacity, whereas the interaction between place and genotype was significant (Table 1). The antioxidant capacity values range from 19.53 to 85.39% in L1 and 15.46 to 86.26% in L2. Mean antioxidant capacity values were 34.78 and 34.55 in L1 and L2, respectively.

The results are similar to those reported previously. Kaur et al. (2017) find that the mean value of antioxidant capacity (DPPH) in grains of ten rice cultivars was 35.0%. However, Bhat & Riar (2017) measured antioxidant capacity (% DPPH) in seven rice brans in methanol, and they found that the values of antioxidant capacity in rice bran ranged from 67.3 to 91.6%. The range of antioxidant capacity in their study is much higher than the range in this study. The previous reports indicated that antioxidant capacity was more elevated in bran rice than whole grain rice.

Fig. 2. Dendrogram of 24 landrace rice genotypes based on ferulic acid content, antioxidant capacity (DPPH) and grain yield.

In this study, G5 had the highest antioxidant capacity (85.39%) in Nakhon Nayok (L1), followed by G23 (82.94%) and G6 (68.28%), whereas G3 has the lowest antioxidant capacity (19.53%). In Sakon Nakhon location (L2), G23 has the highest antioxidant capacity (86.26%) followed by G5 (84.17%) and G6 (68.13%), whereas G21 is the lowest for antioxidant capacity (15.46%). The results indicate that G5, G6, and G23 are good parents for improving antioxidant capacity in rice.

Cluster Analysis

Twenty-four landrace rice genotypes have been divided into three groups (similar coefficient

= 65 %) based on ferulic acid content, antioxidant capacity, and grain yield (Fig. 2). Group 1 consisted of 15 genotypes with moderate ferulic acid content, high antioxidant capacity, and low yield. Group 2 has only G24 with white pericarp, the highest number of panicles per plant, and grain yield, but it has the most deficient ferulic acid and the lowest antioxidant capacity. Group 3 has high ferulic content, moderate antioxidant capacity, and moderate grain yield.

The objectives of this study are to evaluate the diversity of ferulic acid content and to identify the best genotypes for use in a breeding program aiming to develop superior genotypes for ferulic content and yield by grouping the landrace rice into three groups based on ferulic acid content, antioxidant capacity and grain yield. For example, cluster 2 is characterized by high grain yield, and G24 was the only member of this group. Group 3 is characterized by high ferulic acid content. Group 3, consisting of G4 and G22, should be particularly interesting for breeding programs because they had high ferulic acid content. The results indicate that grain yield is not related to ferulic acid content. G24 has a high yield, whereas G4 and G22 have high ferulic acid content. However, all of them can use as parental lines in the breeding program for high ferulic acid content and grain yield.

CONCLUSION AND SUGGESTSION

Rice accessions grown in the Northeast has higher grain yields than those grown in the central region of Thailand, which shows higher vegetative growth. Still, their performance for ferulic acid content and antioxidant capacity is similar. Variations in grain yield, yield components ferulic acid content, and antioxidant capacity are observed among rice accessions in both locations.

The interactions between site and genotype are significant for all characters under study. However, the genotypes performing well across areas for individual characters are identified. The interesting genotypes include G24 with high grain yield, G4, and G22 with high ferulic acid content. These genotypes should be used as parents to generate segregating populations for further selections of superior genotypes or crossed with high-yielding modern varieties to improve ferulic acid content. However, the table quality of cooked rice is an essential character for the consumers’ acceptance. Disease resistance, insect pest resistance, and tolerance to adverse environments are also significant, and these characters should be further evaluated.

ACKNOWLEDGEMENT

The authors are grateful to King Mongkut’s Institute of Technology Ladkrabang [2563-02-04- 008] for providing financial supports to this research.

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