Acta agriculturae Slovenica, 121/1, 1–10, Ljubljana 2025
doi:10.14720/aas.2025.121.1.19926 Original research article / izvirni znanstveni članek
Beneficial effect of organic and inorganic forms of selenium on yield and 
nutritional characteristics of beetroot
Nadezhda GOLUBKINA 1, 2, Vladimir ZAYACHKOVSKY 1, Pavel POLUBOYARINOV 3, Zarema AMA-
GOVA 4, Agnieszka SĘKARA 5, Otilia Cristina MURARIU 6, Alessio Vincenzo TALLARITA 7, Gianluca 
CARUSO 7
Received October 06, 2024; accepted December 18, 2024
Delo je prispelo 6. oktober 2024, sprejeto 18. december 2024
1 Federal Scientific Vegetable Center, Moscow region 143072, Russia
2 Corresponding author: segolubkina45@gmail.com; tel.+7-903-118-50-30 (Nadezhda Golubkina)
3 Medical Faculty, Department of General and Clinical Pharmacology, Penza State University, 440026 Penza, Russia
4 Chechen Scientific Institute of Agriculture, 366021Gikalo, Grozny, Chechen republic, Russia
5 Department of Horticulture, Faculty of Biotechnology and Horticulture, University of Agriculture, 31-120 Krakow, Poland
6 Department of Food Technology, ‘Ion Ionescu de la Brad’ Iasi University of Life Sciences, 700490 Iasi, Romania
7 Department of Agricultural Sciences, University of Naples Federico II, 80055 Naples, Italy
Beneficial effect of organic and inorganic forms of selenium 
on yield and nutritional characteristics of beetroot
Abstract: Beetroot (garden beet) is an essential compo-
nent of the human diet and a source of biologically active com-
pounds, valuable for the pharmaceutical and food industry. To 
increase the content of essential nutrients and develop a func-
tional food product with enhanced antioxidants, the effect of 
foliar sodium selenate and selenocystine supply on yield and 
biochemical characteristics of two table beet cultivars (Marusia 
and Nezhnost) was assessed. Compared to the untreated con-
trol, foliar application of 26.4 mM sodium selenate increased 
root yield by 1.20-1.25 times, monosaccharide content by 1.49-
2.25 times, betalain pigments by 1.56-2.17 times and total an-
tioxidant activity (AOA) by 1.38-1.79 times, whereas the sele-
nocystine supply increased the same parameters by 1.44-1.85, 
1.64-3.4, 1.28-1.50 and 1.31-1.33 times, respectively. Compared 
to pulp, root peel demonstrated 2-2.6 times higher levels of 
betalain pigments, 1.9-2.4 times higher levels of polyphenols 
(TP), and 1.5-2.2 times higher antioxidant activity. Significant 
varietal differences in biochemical characteristic changes due 
to organic and inorganic Se supply were recorded. Taking into 
account the relatively low Se biofortification levels of roots (3-
3.5 in pulp and 7-12 in peel), the results of the present research 
prove the importance of Se application mostly to improve beet-
root yield, antioxidant content, including betalain pigments, 
and root peel utilization as a significant source of pharmaceu-
ticals.
Key words: Beta vulgaris L. ssp. vulgaris var. vulgaris; anti-
oxidant status; betalain pigments; selenate; selenocystine; yield
Ugodni učinki organskih in anorganskih oblik selena na pri-
delek in prehranske lastnosti rdeče pese 
Izvleček: Rdeča pesa je bistvena sestavina človeške 
prehrane in vir biološko aktivnih snovi, ki so pomembne 
za farmacevtsko in prehrambeno industrijo. Za povečanje 
vsebnosti esencialnih hranil in razvoj funkcionalnih preh-
rambenih produktov s povečano vsebnostjo antioksidantov 
je bil ocenjen vpliv foliarnega dodajanja natrijevega selenata 
in selenocistina na pridelek in biokemične lastnosti dveh sort 
rdeče pese (Marusia in Nezhnost). V primerjavi s kontrolo 
je foliarno dodajanje 26,4 mM natrijevega selenata povečalo 
pridelek rdeče pese za 1,20-1,25 krat, vsebnost monosahari-
dov za 1,49 do 2,25 krat, vsebnost betalaina za 1,56-2,17 krat 
in celokupno antioksidacijsko aktivnost (AOA) za 1,38-1,79 
krat. Dodajanje selenocistina je iste paramatre povečalo za 
1,44-1,85, 1,64-3,4, 1,28-1,50 in 1,31-1,33 krat. V primerjavi 
s pulpo je olupek rdeče pese izkazal 2-2,6 krat večje vsebnost 
betalaina, 1,9-2,4 krat večje vsebnosti polifenolov (TP) in 1,5-
2,2 krat večjo antioksidacijsko aktivnost. Pri dodatkih organ-
skega in anorganskega Se so bile ugotovljene tudi značilne ra-
zlike v biokemičnih lastnostih med sortama rdeče pese. Glede 
na relativno majhno kopičenje Se v koreninskem gomolju 
rdeče pese (3-3,5 krat v pulpi in 7-12 krat v olupu) rezultati 
raziskave dokazujejo pomen dodajanja selena, predvsem za 
povečanje pridelka, vsebnosti antioksidantov vključno z beta-
lainom in uporabo olupkov kot pomemben vir farmacevtsko 
zanimivih snovi.
Ključne besede: Beta vulgaris L. ssp. vulgaris var. vulgaris; 
stanje antioksidantov; betalaini; selenate; selenocistin; pridelek
Acta agriculturae Slovenica, 121/1 – 20252
N. GOLUBKINA et al.
1 INTRODUCTION
Beetroot (Beta vulgaris L. ssp. vulgaris var. vulgaris) 
is one of the most important root vegetables, an out-
standing source of biologically active compounds and 
nutrients, such as carbohydrates, betalain pigments (Da 
Silva et al., 2019), polyphenols and vitamins (Wruss et 
al., 2015). Among sugar beet, fodder beet, mangold (leaf 
beet) and beetroot, the latter plays a special role in hu-
man nutrition, health maintenance and pharmacology 
(Zhang et al., 2016). 
Betalains are known to be the main antioxidants in 
beetroot (Czapski et al., 2009), and have important ef-
fects such as cardio-protective and analgesic effects (Lun-
dberg & Weitzberg, 2005; Sadowska-Bartosz & Bartosz, 
2021), as well as antimicrobial, anticancer, antilipidemic 
activity, hepato- and neuroprotective, antidiabetic, anti-
inflammatory and immuno-modulatory, reduce systolic 
and diastolic blood pressure, and normalize blood glu-
cose level (Fu et al., 2020). Furthermore, betalain pig-
ments of beetroot are highly valued as food coloring pig-
ments (Chikara et al., 2019), thus contributing to quality 
improvement. Different factors affect beetroot yield and 
quality, such as genetic peculiarities, environmental con-
ditions, light intensity, soil characteristics, fertilization 
technique including microbial supply, water availability, 
etc. (Agic et al., 2018), phytohormones and growth stim-
ulators, humic and amino acids (El-Gamal et al., 2016), 
soil bacteria (Rašovský et al., 2022). 
In recent years, much attention has been paid to 
growth stimulation and antioxidant properties of Se 
compounds (Hegedűsová et al., 2021; Khan et al., 2023). 
At low concentrations, Se may promote photosynthesis, 
enhance protein synthesis, protect plants against biotic 
and abiotic stresses, elicit monosaccharide increase, and 
activate the formation of phytohormones (Liu et al., 
2023). 
Biofortification of beetroot with Se has not been a 
common technique so far. Only Sentkowska & Pyrzynska 
(2023) described the accumulation of SeMet in beetroot 
juice, though the Se biofortification conditions have not 
been indicated. Besides, in previous experiments, low 
efficiency of foliar Se biofortification of root vegetables, 
such as carrots, was recorded (De Oliveira et al., 2018). 
According to the Periodic Table of Elements, Se mimics 
the chemical properties of S, forming appropriate salts 
(selenates Se+6, and selenites Se+4) and Se-amino acids 
(Se-2): selenomethionine (SeMet) and selenocysteine (Se-
Cys). Among them, selenates are the most mobile, sele-
nites the most toxic and Se-amino acids are characterized 
by the highest bioavailability to plants (Dinh et al., 2019). 
Up to date, selenates have been used most frequently for 
plant biofortification (Malagoli et al., 2015), whereas Se-
amino acid application was restricted because of their 
high cost. In 2022, an effective non expensive synthesis 
of selenocystine (SeCys2) was developed (Poluboyarinov 
et al., 2022), providing the opportunity to investigate this 
compound’s efficiency for plant biofortification more in-
tensively.
The present work aimed to evaluate the efficiency of 
sodium selenate and selenocystine (SeCys2) foliar supply 
on yield and nutritional quality of beetroot.
2 MATERIAL AND METHODS
2.1 EXPERIMENTAL DESIGN
The research was conducted on beetroot (Beta vul-
garis L. ssp. vulgaris var. vulgaris) in 2022-2023 at the ex-
perimental fields of Federal Scientific Vegetable Center, 
Russia (55°39.510 N, 37°12.230 E). The mean values of 
monthly temperature and humidity during the crop cy-
cles are presented in Table 1.
Plants were grown in a loam sod-podzolic soil with 
the following characteristics: pH 6.2; 2.12 % organic mat-
ter; 1.32 mg-eq 100 g-1 hydrolytic acidity; 18.5 mg kg-1 
mineral nitrogen; 21.3 mg kg-1 ammonium nitrogen; sum 
of the absorbed bases as much as 93.6  %; 402 mg kg-1 
mobile P; 198 mg kg-1 exchangeable K; 1 mg kg-1 S; 10.95 
mg kg-1 Ca; 2.05 mg kg-1 Zn; 0.86 mg kg-1 B; and 220 µg 
kg-1 Se. The soil quality was assessed using the certified 
methods described in the agrochemical workshop (Cart-
er & Gregorich, 2008), and its mineral composition was 
determined by an AAS Shimadzu GFA-7000 spectropho-
tometer (Shimadzu, Kyoto, Japan). 
Seeds were sown on 8-10 May with a density of 2.9 
plants per m2 (50 × 70 cm). The experimental protocol 
was based on the factorial combination between two red 
beetroot cultivars selected at the Federal Scientific Veg-
etable Center (Nezhnost and Marusia) and two Se treat-
ments (50 mg l-1 of sodium selenate solution, 26.4 mM; 
Table 1: Mean values of monthly temperature and precipitation 
in 2022 and 2023
Month
Temperature (oC) Precipitation (mm)
2022 2023 2022 2023
May 10.7 12.7 61 35
June 18.9 16.8 42 71
July 20.7 18.5 91 151
August 21.9 19.7 4 63
September 10.1 15.0 75 6
October 7.2 5.5 58 114
Acta agriculturae Slovenica, 121/1 – 2025 3
Beneficial effect of organic and inorganic forms of selenium on yield and nutritional characteristics of beetroot
87 mg l-1 of SeCys2 solution, 26.4 mM) plus an untreated 
control (water foliar spray). The plants were sprayed with 
the mentioned solutions twice: at the stage of beetroot 
formation (10-13 July) and 14 days later (1-4 August). A 
split plot design was used for the treatment distribution 
in the field, with three replicates, and each experimen-
tal unit covered a 9.8 m2 surface area. Before sowing, the 
soil was accurately ploughed at 40 cm depth, and during 
the growing season, hoeing and manual weeding were 
carried out according to the needs determined through 
constant monitoring. The fertilization was performed 
twice during the crop cycles (30 June and 30 July) using 
30 kg ha-1 of N15P15K15. The irrigation was activated when 
the soil humidity dropped to 80 % of the available water 
capacity at 20 cm depth. Plants were harvested on 4-8 
October.
2.2 SAMPLE PREPARATION 
After harvesting and removing soil particles, the 
roots were separated from the aerial parts of 10 plants, 
washed with distilled water, dried with filter paper, and 
0.5 mm peel was removed using a special knife. Both 
root pulp and peel were homogenized and used to deter-
mine betalain pigments, nitrates, and total dissolved sol-
ids (TDS). The remainder of the beetroot fractions was 
dried at 70 °C to constant mass and homogenized, and 
the resulting powders were used to determine the total 
antioxidant activity (AOA), total polyphenols (TP), and 
carbohydrate content.
2.3 DRY MATTER 
The dry matter content was determined gravimetri-
cally by drying beetroot samples at 70 °C for 72 hours. 
The results were expressed as a mass/mass percentage of 
dry matter (% m/m).
2.4 NITRATES  
Nitrates in beetroot pulp samples were assessed us-
ing ion-selective electrode with an ionomer Expert-001 
(Econix Inc., Moscow, Russia). 
2.5 TOTAL DISSOLVED SOLIDS (TDS)
Total dissolved solids were analyzed on water ex-
tracts of beetroot pulp using a portable conductometer 
HM Digital TDS-3 (South Korea, Seoul). The results 
were expressed in mg kg-1 d. m.
2.6 SELENIUM 
The selenium content was measured using the mi-
cro-fluorimetric method based on the acidic digestion of 
dried homogenized samples with a mixture of nitric and 
perchloric acids, subsequent conversion of selenate (Se+6) 
to selenite (Se+4) using a solution of 6 N HCl and fluores-
cence value determination of piazoselenol, formed as a 
result of a condensation between Se+4 and 2,3-diaminon-
aphtalene (Alfthan, 1984). The analysis was performed in 
hexane at λ emission 519 nm and λ excitation – 376 nm. 
As an external standard, Se-fortified mitsuba stem pow-
der with a Se content of 1865 µg kg−1 (Federal Scientific 
Vegetable Center) was used. The results were expressed 
in µg kg-1 d m, as mean of three replications.
2.7 TOTAL POLYPHENOLS (TP) 
The total polyphenols (TP) were determined in 70 % 
ethanol extracts of dried peel/pulp samples using the Fo-
lin–Ciocâlteu colorimetric method with some modifica-
tions (Golubkina et al., 2020). The extraction of samples 
was performed at 80 °C (1 h.) using a 70 % ethanol/water 
solution while the condensation with Folin–Ciocâlteu re-
agent was managed in the presence of saturated Na2CO3 
solution at room temperature. The polyphenol concen-
tration was calculated based on the absorption value of 
the resulting mixture at 730 nm by a spectrophotometer 
(Unico 2804 UV, Suite E Dayton, NJ, USA) using the ex-
ternal standard solution of 0.02 % gallic acid. The results 
were expressed as mg of gallic acid equivalent per g of 
dry mass (mg GAE g-1 d. m).
2.8 ANTIOXIDANT ACTIVITY (AOA) 
The antioxidant activity of beet roots and leaves was 
assessed on 70  % ethanolic extracts of dry samples us-
ing a redox titration method (Golubkina et al., 2020). The 
values were expressed in mg gallic acid equivalents (mg 
GAE g-1 d. m.).
2.9 BETALAIN PIGMENTS
The betalain pigment analysis was carried out spec-
trophotometrically on water extracts of homogenized 
beetroot pulp and peel using the absorption values at 
535 nm (betacyanins, extinction 60,000) and 485 nm 
(betaxantins, extinction 48,000) according to Bucur et al. 
(2016). The results were expressed in mg g-1 f. m.
Acta agriculturae Slovenica, 121/1 – 20254
N. GOLUBKINA et al.
2.10 SUGARS 
The monosaccharides were determined using the 
ferricyanide colorimetric method, based on the reac-
tion of monosaccharides with potassium ferricyanide 
(Swamy, 2008). Total sugars were analogically deter-
mined after acidic hydrolysis of water extracts with 
20  % hydrochloric acid. Fructose was used as an ex-
ternal standard. The results were expressed in % per 
dry mass.
2.11 STATISTICAL ANALYSIS 
The data were statistically processed using the 
analysis of variance (ANOVA), and the mean separa-
tions were performed through the Duncan’s test at p < 
0.05 probability level, using the SPSS software version 
29 (IBM, Armonk, NY, USA).
3 RESULTS AND DISCUSSION
3.1 YIELD AND BIOMETRICAL PARAMETERS 
Our previous investigation regarding Savoy cab-
bage biofortification with Se demonstrated a signifi-
cantly higher growth stimulation effect of selenocys-
tine than sodium selenate (Antoshkina et al., 2023). 
The present results were in accordance with the men-
tioned observation indicating high prospects of se-
lenocystine supply in beetroot production (Table 2, 
Figure 1). Furthermore, the possibility of increasing 
beetroot yield by 1.44-1.66 times using selenocystine 
and by 1.20-1.26 times via foliar application of sodium 
selenate was recorded under low Se concentration not 
exceeding 26.4 mM. In this respect, similar beneficial 
effect of inorganic forms of Se was recorded on the two 
cultivars studied and significant varietal differences in 
the case of selenocystine application (Figure 1). The 
data presented in Table 2 also indicate the increase of 
root marketability due to Se supply with higher effi-
ciency of organic Se compared to sodium selenate. No 
significant differences in the dry matter content be-
tween control and Se-treated plants were recorded. 
3.2 CARBOHYDRATES, NITRATES AND TOTAL 
DISSOLVED SOLIDS (TDS)
The accumulation of carbohydrates is one of the 
most important characteristics of beetroot. In the pre-
sent study, Se treatment did not change the total sugar 
content in roots but significantly increased the con-
centration of minor monosaccharides (Table 3). 
The results were in accordance with the corre-
sponding phenomenon of monosaccharide increase 
for environmental stress alleviation, improving pho-
tosynthesis, osmotic homeostasis, protein synthesis 
and membrane stabilization (Sami et al., 2016). De-
Parameter Treatment ‘Nezhnost’ ‘Marusia’
Mass (g) Control 157 ± 15 c 165 ± 16 b
Se+6 197 ± 19 b 198 ± 19 a
SeCys2 290 ± 28 a 237 ± 25 a
Yield (t ha -1) Control 46.9 ± 4.7 c 49.5 ± 4.8 c
Se+6 59.1 ± 6.0 b 59.4 ± 5.8 b
SeCys2 78.0 ± 7.7 a 71.2 ± 7.0 a
Marketability 
level (%)
Control 91.0 ± 0.9 e 94.0 ± 0.9 cd
Se+6 93.5 ± 0.9 d 96.2 ± 0.9 ab
SeCys2 95.6 ± 0.9 bc 98.2 ± 0.9  a
Length (cm) Control 12.2 ± 1.0 a 5.1 ± 0.5 a
Se+6 12.6 ± 1.0 a 5.5 ± 0.5 a
SeCys2 12.2 ± 1.0 a 5.5 ± 0.5 a
D i a m e t e r 
(cm)
Control 5.0 ± 0.5 b 5.1 ± 0.5 b
Se+6 5.2 ± 0.5 a 5.4 ± 0.5 b
SeCys2 5.9 ± 0.5 a 6.0 ± 0.6 a
Dry mass (%) Control 18.8 ± 1.7 a 18.8 ± 1.8 a
Se+6 18.4 ± 1.6 a 19.0 ± 1.8 a
SeCys2 17.5 ± 1.6 a 18.5 ± 1.8 a
Table 2: Yield, biometrical and growth parameters of beet roots
For each parameter, values with the same letters do not differ statisti-
cally according to Duncan test at p < 0.05.
Figure 1: Changes in beetroot yield due to Se application. 
Values with the same letters do not differ statistically according 
to Duncan test at p < 0.05
Acta agriculturae Slovenica, 121/1 – 2025 5
Beneficial effect of organic and inorganic forms of selenium on yield and nutritional characteristics of beetroot
spite the significant varietal differences in Se effect on 
monosaccharide accumulation, SeCys2 showed higher 
efficiency than selenate, increasing the monosaccha-
ride levels by 1.8-3.4 times compared to 1.5-2.2 times 
recorded under sodium selenate application. Never-
theless, considering the low monosaccharide accu-
mulation levels in beetroot, the mentioned phenom-
enon did not have a significant effect on disaccharides 
whose concentration was over 10 times higher than 
the levels of monosaccharides.
Beetroot belongs to a group of vegetables capable 
of accumulating high concentrations of nitrates, thus 
being highly valuable in supporting human health, 
preventing hypertension and protecting against car-
diovascular diseases (Brzezinska-Rojek et al., 2023; 
Dos S.Baião et al., 2020) via regulation of gene expres-
sions of proteins and enzymes involved in the nitric 
oxide synthesis. Selenium is known to affect nitrogen 
metabolism, usually decreasing the nitrate content in 
plants (Golubkina et al., 2018; Pilon-Smits & Quinn, 
2010). In the present investigation, we did not record 
significant differences between beetroot plants sup-
plied with Se and control plants regarding nitrate ac-
cumulation. 
The lack of significant differences in total dis-
solved solids (TDS) between control and Se treated 
plants corresponds to the same situation referring to 
total sugars in roots. 
3.3 BETALAIN PIGMENTS
Among beetroot natural antioxidants, betalain 
pigments are considered the most valuable (Fu et al., 
2020; Sadowzka-Nartosz & Nartosz, 2021). The results 
of the present investigation revealed that sodium se-
lenate supply increased the total betalain content by 
2.16 times (‘Marusia’) and 1.55 times (‘Nezhnost’), 
while selenocystine produced a lower effect, with 1.5 
and 1.28 times increase, respectively (Table 4, Figure 
2). Contrary, though the initial levels of betalain pig-
ments were much higher in peel than in pulp, the pig-
ment content changes due to Se application were low-
er in ‘Nezhnost’ (1.18-1.19 for both forms of Se) and 
higher in ‘Marusia’ (1.39 (SeCys2)-1.64 (Se
+6) times). 
Betalain peel/pulp ratio in control and SeCys2 treated 
plants of both cultivars was equal to 2.54, whereas a 
slightly lower value was recorded for selenate supplied 
plants (2.27). 
Furthermore, the varietal differences between 
the two cultivars tested revealed that the magnitude 
of betalain pigment increase upon Se supply may be 
due to either differences in the intensity of pulp or peel 
pigment accumulation (Figure 2).
According to literature data, red pigments beta-
cyanins account for approximately 75–95  % of beet-
root pigments, the remaining 5–25  % being yellow 
betaxanthins (Delgado-Vargas et al., 2000; Ninfali & 
Angelino, 2013). Betaxanthin content in roots of in-
vestigated cultivars reached 67-68  % and showed a 
slight tendency to the increase up to 70-71  % under 
Parameter Treatment cv. Nezhnost cv. Marusia
Monosaccha-
rides (% d. m.)
Control 3.76 ± 0.33 c 2.58 ± 0.22 b
Se+6 8.15 ± 0.80 b 3.85 ± 0.34 a
SeCys2 12.79 ± 1.12 a 4.22 ± 0.40 a
Total sugar 
(% d. m.)
Control 72.50 ± 7.01 a 73.10 ± 7.00 a
Se+6 68.00 ± 6.62 a 67.80 ± 6.55 a
SeCys2 66.80 ± 6.45 a 66.20 ± 6.51 a
Nitrates 
(mg kg-1 d. m.)
Control 1055 ± 110 a 1282 ± 120 a
Se+6 1204 ± 110 a 1442 ± 140 a
SeCys2 1159 ± 110 a 1429 ± 140 a
TDS (%) Control 3.97 ± 0.40 a 3.80 ± 0.35 a
Se+6 4.28 ± 0.40 a 4.14 ± 0.40 a
SeCys2 3.76 ± 0.38 a 4.37 ± 0.42 a
Table 3: Content of carbohydrate, nitrate and total dissolved 
solids in beetroot roots
For each parameter, values with the same letters do not differ statisti-
cally according to Duncan test at p < 0.05.
Figure 2: Effect of selenium biofortification on betalain pig-
ment content in pulp (a) and peel (b) of beetroot. Values with 
the same letters do not differ statistically according to Duncan 
test at p < 0.05
Acta agriculturae Slovenica, 121/1 – 20256
N. GOLUBKINA et al.
Se supply (Table 4). The betacyanin/betaxantin ratios 
were close to 1.9:1 in peel and 2.2:1 in pulp and were not 
significantly affected by Se supply.
The predominant accumulation of betalain pig-
ments in beet root peel is well documented (Kujala et al., 
2002; Slatnar et al., 2015), indicating great prospects of 
peel utilization as a valuable source of natural pigments. 
The significance of high betalain pigment accumu-
lation in peel and pulp of beetroot relates to the nutri-
tional value increase due to Se supply and the possibility 
of betalain utilization as food colorant (Calva-Estrada 
et al., 2022). Indeed, betalains are widely used as food 
colorants due to their prominent and consistent colours 
at pH 3–7. The development of packaging films incor-
porated with betalains is used as the colorimetric indi-
cators and smart packaging films capable of improving 
the functional properties of packaging films, including 
higher water resistance, tensile strength, elongation at 
break, and antioxidant and antimicrobial activities (Abe-
di-Firoozjah et al., 2023).
3.4 TOTAL ANTIOXIDANT ACTIVITY (AOA) 
AND POLYPHENOLS (TP)
According to literature data, beet roots contain a 
significant amount of catechins and polyphenolic acids, 
including ferulic, protocatechuic, vanillic, caffeic and 
others, providing increased antioxidant activity of root 
ethanolic extracts (Kavalcova et al., 2015; Platosz et al., 
2020). The main beet root flavonoids are rutin, kaemph-
erol, rhamnetin, rhamnecitrin and astragalin (Sentkows-
ka & Pyrzynska, 2020).
The analysis of the total antioxidant activity (AOA) 
using 70 % ethanolic extracts of beet roots revealed sig-
nificant increase in the parameter due to Se supplemen-
tation (Table 4, Figure 3). 
Contrary, TP levels did not differ significantly be-
tween control and Se treated plants, reaching 10.9-12.8 
mg GAE g-1 d. m. in pulp and 23.7- 26.2 mg GAE g-1 d. m. 
in peel. The beneficial effect of Se on beetroot antioxidant 
activity was greater in ‘Nezhnost’ than ‘Marusia’ (Figure 
3), contrary to water soluble betalain pigments whose 
level was higher in cultivar Marusia roots, compared to 
‘Nezhnost’ (Figure 3 a,b).
Furthermore, ‘Marusia’ did not demonstrate dif-
ferences in the AOA between organic and inorganic Se 
supply, while ‘Nezhnost’ showed more intensive AOA 
increase under selenate application. The latter phenom-
enon may be connected with varietal differences in poly-
phenol content of roots. However, there is no data about 
the mechanism of Se effect on polyphenol accumulation 
Parameter Treatment
‘Nezhnost’ ‘Marusia’
Pulp Peel Pulp Peel
Betacyanin 
(mg g-1)
Control 1.34 ± 0.15 b 3.40 ± 0.31 a 1.20 ± 0.11 c 3.07 ± 0.29 b
Se+6 2.13 ± 0.20 a 3.98 ± 0.36 a 2.73 ± 0.24 a 5.10 ± 0.49 a
SeCys2 1.81 ± 0.17 a 4.16 ± 0.40 a 1.89 ± 0.16 b 4.34 ± 0.41 a
Betaxantin 
(mg g-1)
Control 0.64 ± 0.06 b 1.79 ± 0.16 a 0.60 ± 0.05 c 1.67 ± 0.15 b
Se+6 0.94 ± 0.09 a 2.14 ± 0.20 a 1.18 ± 0.10 a 2.69 ± 0.24 a
SeCys2 0.72 ± 0.07 b 2.02 ± 0.19 a 0.81 ± 0.08 b 2.27 ± 0.20 a
Total betalain pigments
(mg g-1)
Control 1.97 ± 0.16 b 5.19 ± 0.50 b 1.80 ± 0.17 c 4.74 ±  0.44 b
Se+6 3.07 ± 0.29 a 6.12 ± 0.60 a 3.91 ± 0.36 a 7.79 ± 0.75 a
SeCys2 2.53 ± 0.23 a 6.18 ± 0.60 a 2.70 ± 0.25 b 6.61 ± 0.62 a
AOA 
(mg GAE g-1 d. m.)
Control 20.6 ± 2.0 c 40.5 ± 3.8 b 19.4 ± 1.5 b 41.9 ± 4.0 b
Se+6 36.8 ± 3.3 a 55.9 ± 5.2 a 26.8 ± 2.4 a 49.4 ± 4.0 a
SeCys2 27.0 ± 2.5 b 52.3 ± 5.0 a 25.8 ± 2.3 a 52.4 ± 5.0 a
TP
(mg GAE g-1 d. m.)
Control 11.1 ± 1.0 a 25.8 ± 2.2 a 11.4 ± 1.0 a 25.2 ± 2.3 a
Se+6 11.3 ± 1.0 a 22.7 ± 2.0 a 13.1 ± 1.0 a 24.8 ± 2.3 a
SeCys2 10.4 ± 0.9 a 22.7 ± 2.0 a 13.8 ± 1.0 a 28.6 ± 2.4 a
Table 4: Antioxidant levels in beetroot as affected by organic and inorganic forms of Se
For each parameter, values with the same letters do not differ statistically according to Duncan test at p < 0.05. 
Acta agriculturae Slovenica, 121/1 – 2025 7
Beneficial effect of organic and inorganic forms of selenium on yield and nutritional characteristics of beetroot
and further studies are needed to reveal the mechanism 
of these changes.
3.5 SE ACCUMULATION
Our previous investigations on Se biofortification of 
shallot (Golubkina et al., 2019) and Savoy cabbage (An-
toshkina et al., 2023) demonstrated higher biofortifica-
tion levels under SeCys2 supply, compared to the values 
recorded in selenate treated plants. The present results 
indicate that the mentioned effect greatly depends on 
plant part and varietal differences in beetroot. Indeed, 
beet leaves were the most sensitive to Se supply, able to 
accumulate up to 1200 µg Se kg-1 d. m. in case of Secys2 
treated plants, with 1.35 times lower values in case of se-
lenate supplementation (Table 5). 
A less pronounced effect was recorded in beetroot 
where Se accumulated predominantly in root peel. The 
lowest biofortification levels were recorded in root pulp 
reaching only 3-3.5 times (Figure 4). 
3.6 CORRELATION ANALYSIS
The correlation analysis between the parameters 
tested indicated a significant beneficial effect of pulp 
monosaccharide content and peel Se levels on beet root 
yield and a positive effect of Se on betalain accumulation 
in pulp and peel (Table 6). 
Furthermore, antioxidant activity of fat-soluble an-
tioxidants and root yield were significantly affected by Se 
accumulation both in pulp and peel. Indeed, Se supply 
demonstrated a significant relationship with root yield, 
Figure 3: Effect of organic and inorganic forms of Se on 
antioxidant activity of beet root pulp (a) and peel (b). Values 
with the same letters do not differ significantly according to 
Duncan test at p < 0.05
Plant part Treatment ‘Nezhnost’ ‘Marusia’
Pulp Control 33 ± 3 d 44 ± 4 c
Se+6 120 ± 10 ab 133 ± 13 a
SeCys2 100 ± 9 b 128 ± 11 a
Peel Control 38 ± 3 d 50 ± 5 c
Se+6 345 ± 30 b 361 ± 33 b
SeCys2 458 ± 41 a 355 ± 31 b
Leaves Control 29 ± 2 d 39 ± 3 c
Se+6 900 ± 79 b 910 ± 76 b
SeCys2 1220 ± 98 a 1235 ± 100 a
Table 5: Selenium accumulation in beet roots under organic 
and inorganic Se supply (µg Se kg-1 d. m.)
For each parameter, values with the same letters do not differ statisti-
cally according to Duncan test at p < 0.05. 
Figure 4: Selenium biofortification levels of beet root pulp (a) 
and peel (b). Values with the same letters do not differ statisti-
cally according to Duncan test at p < 0.05
Acta agriculturae Slovenica, 121/1 – 20258
N. GOLUBKINA et al.
betalain pigment accumulation and total antioxidant ac-
tivity. It is interesting that antioxidant characteristics (in-
cluding Se) of beet root peel directly correlate both with 
root yield values and accumulation of water-soluble beta-
lain pigments, and indicate the importance of the ‘edge’ 
effect for plant adaptation (Golubkina et al., 2023).
4 CONCLUSION
From research carried out on selenium biofortifica-
tion of beetroot, it arose that the organic and inorganic 
Se supply to beetroot plants significantly enhanced yield 
and quality of roots, compared to control plants, though 
showing low efficiency in producing beetroots with Se 
levels suitable to compensate Se deficiency in humans. 
Sodium selenate had a significantly higher beneficial ef-
fect on betalain pigment levels and fat-soluble antioxi-
dant content, in comparison with SeCys2, which led to 
higher root yield and monosaccharide levels. Overall, the 
outcome obtained from the present study allows to infer 
that Se biofortification of beetroot plants is a useful strat-
egy to encourage yield and nutritional quality of roots. 
5 FUNDING STATEMENT
This research did not receive any specific grant from 
funding agencies in the public, commercial, or not-for-
profit sectors that could be construed as a conflict of in-
terest or that might have appeared to influence the work 
reported in this paper.
6 AUTHOR CONTRIBUTIONS
 Conceptualization: N.G. and G.C.; formal analy-
sis: N.G., A.S., O.C.M., and A.V.T.; investigation: N.G., 
V.Z., P.P. and Z.A.; methodology: N.G., A.S., O.C.M., and 
A.V.T.; validation, N.G., A.S., O.C.M., and G.C.; draft 
manuscript writing, N.G., O.C.M., and A.V.T.; manu-
script revision and final editing, N.G., A.S., and G.C. All 
authors have read and agreed to the published version of 
the manuscript. 
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