Pigmented radish (Raphanus sativus): Genetic variability, heritability and inter-relationships of total phenolics, anthocyanins and antioxidant activity

Abstract

Radish (Raphanus sativus L.) is an important salad vegetable grown and consumed throughout the world for fleshy roots which has numerous categories-varying in root colour, size, shape and flavour. The uses of coloured radishes in the salads and their anthocyanins as colourants are gaining popularity because of the colour characteristics, health benefits as well as antioxidant activities. However, information on the genetic variability, heritability and interrelationship of total phenolics, anthocyanins and antioxidant activities in pigmented radish is very limited, but prerequisite to initiate breeding programme; and therefore investigated in the present study. Radish genotypes were significantly diverse for all the antioxidants; differed by 4.98-fold for total phenolics, 36.16-fold for anthocyanins content, 4.96-fold for FRAP activity and 4.03-fold for CUPRAC activity; and the genotypes accounted for >97% of total variations. The meager differences between phenotypic and genotypic coefficient of variation reveals the greater role of genotypes and lesser influence of the environment on the biosynthesis and accumulation of antioxidants. Significantly positive correlations along with higher magnitude for anthocyanins content, total phenolics, FRAP activity and CUPRAC activity (r= 0.823 to 0.964) could be used as indirect selection criteria for improving levels of antioxidant compounds. The estimates of heritability and genetic advance indicate the role of additive and non-additive genes for biosynthesis of antioxidants and root development, respectively; therefore, recurrent selection would be the best breeding approach to improve both the traits simultaneously in coloured radish.

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1Scientist (e mail: bksinghkushinagar@yahoo.co.in),
2Scientist (e mail: tanmay_iari@rediffmail.com), 3Scientist (e
mail: pradip9433@gmail.com), 4SRF (e mail: tripathiajay17@
gmail.com), 4Director (e mail: bsinghiivr@gmail.com), 5PC (e
mail: singhvns@gmail.com), AICRP-VC.
Research Articles
Indian Journal of Agricultural Sciences 87 (12): 1600–6, December 2017/Article
Pigmented radish (Raphanus sativus): Genetic variability, heritability and inter-
relationships of total phenolics, anthocyanins and antioxidant activity
B K SINGH1, T K KOLEY2, PRADIP KARMAKAR3, AJAY TRIPATHI4, BIJENDRA SINGH5 and MAJOR SINGH6
ICAR-Indian Institute of Vegetable Research (IIVR), Shahanshahpur, Varanasi, Uttar Pradesh 221 305
Received: 16 April 2017; Accepted: 26 July 2017
ABSTRACT
Radish (Raphanus sativus L.) is an important salad vegetable grown and consumed throughout the world for eshy
roots which has numerous categories– varying in root colour, size, shape and avour. The uses of coloured radishes in the
salads and their anthocyanins as colourants are gaining popularity because of the colour characteristics, health benets
as well as antioxidant activities. However, information on the genetic variability, heritability and inter-relationship of
total phenolics, anthocyanins and antioxidant activities in pigmented radish is very limited, but pre-requisite to initiate
breeding programme; and therefore investigated in the present study. Radish genotypes were signicantly diverse
for all the antioxidants; differed by 4.98-fold for total phenolics, 36.16-fold for anthocyanins content, 4.96-fold for
FRAP activity and 4.03-fold for CUPRAC activity; and the genotypes accounted for >97% of total variations. The
meager differences between phenotypic and genotypic coefcient of variation reveals the greater role of genotypes
and lesser inuence of the environment on the biosynthesis and accumulation of antioxidants. Signicantly positive
correlations along with higher magnitude for anthocyanins content, total phenolics, FRAP activity and CUPRAC
activity (r= 0.823 to 0.964) could be used as indirect selection criteria for improving levels of antioxidant compounds.
The estimates of heritability and genetic advance indicate the role of additive and non-additive genes for biosynthesis
of antioxidants and root development, respectively; therefore, recurrent selection would be the best breeding approach
to improve both the traits simultaneously in coloured radish.
Key words: Anthocyanins, Antioxidants, Correlation, Inheritance, Radish, Raphanus sativus, Variability
Radish (Raphanus sativus L., 2n=2x=18), Brassicaceae
family, is an important vegetable grown and consumed
throughout the world for eshy edible roots (hypocotyls)
which are eaten as crunchy salad, cooked or preserved by
salting, pickling, canning and drying. Also, the soft leaves
are cooked and used as a leafy vegetable. Radish is an
ancient crop, native to the eastern Mediterranean and the
Middle East. Moreover, central China, central Asia and India
appear to have been secondary centers where differing forms
were evolved during the course of domestication. The rst
record about radish consumption in human nutrition date
back to about 2700 BC in the ancient Egypt, however its
cultivation started in China and Korea about 400 BC (George
and Evans 1981, Kaneko and Matsuzawa 1993). Radish has
numerous categories, varying in root colour, size, shape,
avour and period of maturity; moreover differences in leaf
morphology were also observed. The ancient varieties were
long and tapering rather than cylindric, apically bulbous,
elliptic or spherical. The different forms of radishes arose
in the various time sequences, i.e. black radishes were the
earliest in cultivation, white radishes were being cultivated
in Europe by the 1500's, and red and round radishes were
developed in the 1700's. In the West, commonly, the radish
is seen as a small-rooted, short-season vegetable; while in
the Far East and Asian countries, a diverse, large-rooted and
long-season radish is widely grown. In India, it is grown
in one or the other parts of the country almost throughout
the year because of the varied climatic conditions, and its
stable and productive cultivars, economic importance and
increasing demand.
The black to red colour of radish is due to anthocyanins,
the most versatile polyphenols and a class of pigments
responsible for the red, purple and blue colours of many
vegetable, fruits and cereals. They have nutraceutical,
colourant and anti-oxidative properties (Delgado-Vargas
and Paredes-Lopez 2003, Giusti and Wrolstad 2003,
Horbowicz et al. 2008, Pojer et al. 2013, Jing et al. 2014).
Within the plant, they play a role as key antioxidants and
pigments contributing to the colouration of various plant
parts. Given their antioxidant properties, i.e. acting as free
radical scavengers, anthocyanins in general have ability to

1601December 2017]
17
GENETIC VARIABILITY FOR ANTHOCYANINS AND ANTIOXIDANTS IN PIGMENTED RADISH
lower the LDL cholesterol and the risk of cardiovascular
disease (Ross and Kasum 2002, Prior and Wu 2006, Castilla
et al. 2008), to prevent obesity (Prior and Wu 2006, Peng
et al. 2011), to inhibit the formation and progression of
atherosclerosis (Estruch et al. 2004, Iwasaki-Kurashige et
al. 2006), diabetes (Iwasaki-Kurashige et al. 2006), certain
cancers (Ross and Kasum 2002, Prior and Wu 2006, Wang
and Stoner 2008), to improve visual function (Kramer
2004, Ghosh and Konishi 2007), oxidative stresses and
age-related diseases (Tsuda 2012, Pojer et al. 2013). Within
the plant, they play a role as pigments contributing to the
colouration of various plant parts. Moreover, they act as
antioxidants protecting cells against environmental stresses
such as ultraviolet and high intensity light, wounding,
cold temperature and water stress (Mo et al. 1992, Koes
et al. 1993, Li et al. 1993, Dixon and Palva 1995, Holton
and Cornish 1995, Shirley 1996, Chalker-Scott 1999,
Gould et al. 2002, Misyura 2014). Furthermore, uses of
anthocyanins as colourants have gained prominence as a
result of legislative action and consumers’ concerns over
the use of synthetic additives in foods. Among the various
anthocyanins, pelargonidine (acylated pelargonidin-3-
sophoroside-5-glucoside) and cyanidine (acylated cyaniding-
3-sophoroside-5-glucoside) are responsible for red/pink
and purple/violet colour of the roots in radish, respectively
(Giusti and Wrolstad 1996, Tatsuzawa et al. 2010). The
absence of anthocyanins resulted in a white colour. The
uses of coloured radish in the salads or as garnish gaining
popularity in India as it makes salad more nutritious,
healthier and attractive appearance. Radish anthocyanins
have been applied as natural colourants due to their tinctorial
power (i.e. colour intensity), stability, colour characteristics,
health benets as well as antioxidant activities (Giusti and
Wrolstad 1996, Giusti et al. 1998, Matsufuji et al. 2007,
Rahman et al. 2006). Most of the Brassica vegetables are
good source of antioxidants, ultimately beneting the human
and plant health (Singh 2007, Soengas et al. 2011, Singh
et al. 2010, Cartea et al. 2011, Kapusta-Duch et al. 2012).
Generally, the pigmented radish contains higher amounts
of anthocyanins, phenolic compounds and antioxidant
activity than non-pigmented radish. The authors have
estimated 20-250% higher antioxidants in coloured-rooted
radishes as compared to white-rooted commercial/ national
check cultivars, namely Japanese White and Kashi Shweta
(unpublished data). The daily intake of anthocyanins in the
USA diet is estimated to be as much as 180–255 mg/day
(McGhie and Walton 2007). Genetically, the presence or
absence of anthocyanins in grape skin is qualitative in nature,
i.e. controlled by oligogenes, while anthocyanins content is
quantitative character and controlled by polygenes (Liang et
al. 2009). The antioxidants and yield contributing traits are
genetically regulated and can be improved simultaneously
through various breeding approaches. Hence, the opportunity
to develop coloured radish genotypes/varieties with
higher antioxidants is great. To the best of our knowledge
and available literatures, very fragmented information
is available on genetic variability, heritability and inter-
relationship of total phenolics, anthocyanins and antioxidant
activities in radish. Therefore, the present study was assumed
with the objective to estimate antioxidants’ variability, their
heritability and inter-relationship for possible exploitation
to breed the genotypes/varieties having higher antioxidant
content/activity as well as better yield potential.
MATERIALS AND METHODS
Twenty-four lines, including eleven of pink-rooted and
thirteen of purple colour, comprised the basic experimental
materials, were evaluated for this study. All the coloured-
rooted genotypes are developed and maintained at ICAR-
Indian Institute of Vegetable Research (ICAR-IIVR),
Shahanshahpur, Varanasi, Uttar Pradesh. The details of
morphological traits of basic experimental materials used are
given in Table 1.
Crop was raised during 2014-2015 at the Research
Farm, ICAR-IIVR, Varanasi, Uttar Pradesh. The Farm is
located at 25°10’55’’ N latitude and 82°52’36’’ E longitude
Table 1 Details of basic experimental materials
Genotype Root colour-
Exterior
Root shape Leaf
division-
Incision
(LDI)
Petiole
colour
VRRAD 88 Pink* Iciclical Lyrate Green
VRRAD 125 Pink Iciclical Lyrate Pink
VRRAD 126 Light pink Iciclical Lyrate Green
VRRAD 127 Pink Elliptical Sinuate Pink
VRRAD 127-1 Pink Obtriangular Sinuate Pink
VRRAD 128 Purple Iciclical Lyrate Purple
VRRAD 128-1 Purplish
white
Iciclical Sinuate Purple
VRRAD 128-2 Light purple Iciclical Sinuate Purple
VRRAD 129 Purple* Iciclical Lyrate Purple
VRRAD 130 Pink Iciclical Lyrate Pink
VRRAD 130-1 Light pink Iciclical Lyrate Green
VRRAD 130-2 Purple Iciclical Lyrate Purple
VRRAD 130-3 Dark purple Iciclical Lyrate Purple
VRRAD 130-4 Dark purple Iciclical Lyrate Purple
VRRAD 131 Purple Iciclical Lyrate Purple
VRRAD 131-1 Purplish
white
Iciclical Lyrate Purple
VRRAD 131-2 Pink Iciclical Sinuate Pink
VRRAD 132 Purple Iciclical Lyrate Purple
VRRAD 134 Light purple Obtriangular Lyrate Purple
VRRAD 135 Purple Iciclical Lyrate Purple
VRRAD 136 Pink Obtriangular Lyrate Pink
VRRAD 143 Pink Iciclical Lyrate Pink
VRRAD 143-1 Pink Iciclical Sinuate Green
VRRAD 143-2 Purple Iciclical Sinuate Purple
*Shoulder colour

1602 [Indian Journal of Agricultural Sciences 87 (12)
18
SINGH ET AL.
with an altitude of 85 m above the mean sea level,
and receives an annual rainfall of 1050-1100 mm. Soil
preparation, sowing and other agronomic practices were
carried out uniformly to get better morphological expression
(Singh and Karmakar 2015). The seeds were sown at 1.0-1.5
cm interval in double row of 7-8 cm apart and 25-28 cm
wide ridge with the spacing of about 80 cm between each
pair of ridges. Each genotype comprises three ridges of
5.50 m long and triplicated in a randomized block design.
The crop was unvaryingly fertilized with optimum doses
of chemical fertilizers, i.e. 80 kg N, 40 kg P2O5 and 30 kg
K2O per hectare which were supplied as urea, single super
phosphate and muriate of potash, correspondingly. Half of
the N, and full P2O5 and K2O were applied as basal dressing
at time of ridges preparation, while remaining half dose of
N was furrow-dressed at 30 days after sowing. After seed
germination, thinning was done 10-12 days after sowing
keeping the distance in between the plants about 5-6 cm
apart for proper root development.
Each genotype in replicated trial was harvested at
marketable stage (horticultural maturity) i.e. 50 days after
sowing. Ten roots of each randomly selected and leaves
were cut manually. The roots were washed thoroughly
with normal tap water to remove adhering soil and other
extraneous matters. A representative of the edible root part
was taken for subsequent assay and estimation on fresh
weight (FW) basis.
Radish was minced with stainless steel knife and
homogenized using a warring blander. An aliquot of 25
g the commuted radish was extracted with 100 ml of
methanol/0.1% HCl (v/v) for 2 h under dark condition. After
centrifugation at 13000 rpm for 15 min, the supernatant
was recovered and the extract residues were re-extracted
with the same method. The combined supernatant were
evapourated to dryness and re-dissolved in distilled water.
The total monomeric anthocyanins content (anthocyanins)
was determined through measuring absorbance at 520 nm
against the blank on a UV–Visible spectrophotometer by
the pH-differential method (Wrolstad et al. 2005). Pigment
content was expressed as total monomeric anthocyanins
equivalents (μg/g FW).
Water soluble phytochemicals of radish were extracted
according to the method reported previously (Chu et al.
2002) with slight modication. For the extraction of soluble
nutraceuticals, 5 g of the edible part of radish was weighed
and homogenized with 80% ethanol (1:2 w/v) using a
chilled warring blender for 5 min. The sample was then
further homogenized using a polytron homogenizer for
an additional 3 min to obtain a thoroughly homogenized
sample. The homogenates were centrifuge at 13000 rpm
for 15 min. The supernatant were collected and stored at
-20 °C until analysis of total phenolics, ferric reducing
antioxidant power (FRAP) and cupric reducing antioxidant
capacity (CUPRAC) activity.
Total phenol was estimated spectrophotometrically
using Folin–Ciocalteu reagent (Singleton et al. 1999).
Aliquots (100 μl) of hydrophilic extract were mixed with 2.9
ml of deionized water, 0.5 ml of Folin–Ciocalteu reagent and
2.0 ml of 20% Na2CO3 solution. The mixture was allowed
to stand for 90 min and absorption was measured at 760 nm
against a reagent blank in UV–Visible spectrophotometer.
Results were expressed as gallic acid equivalent (mg
GAE/100 g FW).
The FRAP activity was performed according to the
procedure described by Benzie and Strain (1996). FRAP
reagent was prepared by mixing 300 mM acetate buffer (pH
3.6), 10 mM TPTZ in 40 mmol HCl and 20 mmol FeCl3 in
the ratio 10:1:1 (v/v/v). Three milliliter (3 ml) of the FRAP
reagent was mixed with 100 μl aliquot of hydrophilic extract
in a test tube and vortexed in the incubator at 37°C for 30
min in a water bath. Reduction of ferric-tripyridyltriazine
to the ferrous complex formed an intense blue colour which
was measured on a UV–Visible spectrophotometer at 593
nm. Results were expressed in terms of Trolox equivalent
(μmol TE/g FW).
The cupric ion reducing antioxidant capacity of root was
determined according to the method of Apak et al. (2008).
Briey, according to the protocol 100 μl of hydrophilic
extract was mixed with 1 ml each of CuCl2 solution (1.0
× 10-2 mol/l), neocuproine alcoholic solution (7.5 × 10-3
mol/l), and NH4Ac (1 mol/l, pH 7.0) buffer solution and
1 ml of water to make the nal volume 4.1 ml. After 30
min, the absorbance was recorded at 450 nm against the
reagent blank. Standard curve was prepared using different
concentration of Trolox and results were expressed in terms
of μmol TE/g FW.
The data were analysed statistically for analysis
of variance (Panse and Sukhatme 1967), estimation of
variability (Burton and DeVane 1953) and correlation (Searle
1961). The standard error for genotypes was calculated as
per Singh and Chaudhary (1977). The variability estimates
(genotypic and phenotypic variance; and genotypic and
phenotypic coefcient of variation) were worked out
through analysis of variance, while correlation coefcients
were determined by covariance and variance between traits.
Broad-sense heritability (h2b) for each trait was calculated
by multiplying the ratio of genotypic variance (Vg) to
phenotypic variance (Vp) with 100, i.e. h2b=(Vg/Vp)*100.
Moreover, genetic advance (GA) as percentage of mean
was computed through dividing the factor of square root of
phenotypic variance (Vp½), h2b and selection differential
constant (k) at 5% (i.e. 2.06) by its mean, i.e. GA as % of
mean=(Vp½* h2b*k)/mean.
RESULTS AND DISCUSSION
Nowadays, the breeders are giving due consideration
for the improvement of nutritional qualities as well as yield
potential. Like yield, nutritional improvement in crops also
requires sufcient genetic variation for phytochemical in
the gene pool. The mean square (Table 2) showed that
total phenolics, anthocyanins, FRAP value and CUPRAC
value, and root weight of radish varied signicantly (P <
0.01) among the 24 genotypes of coloured radish. Highly
signicant mean squares for antioxidants and root weight

1603December 2017]
19
phytochemicals (Chander et al. 2008, Singh et al. 2011,
Mahan et al. 2013, Harakotr et al. 2015). The magnitudes of
Vp and PCV were slightly higher than their corresponding
Vg and GCV for antioxidants, but the magnitude was wider
for root weight. The lower differences between Vp and
Vg, and PCV and GCV for total phenolics, anthocyanins,
FRAP and CUPRAC activity indicate the higher role of
genotypes and lesser inuence of the environment on the
biosynthesis and accumulation of antioxidants because the
anthocyanins’ presence and content is governed by dominant
polygenes (Liang et al. 2009). While, there is considerable
impact of environments on root yield of radish indicated
by comparatively higher differences between Vp and Vg,
and PCV and GCV. The root yield is a complex trait that
depends on several growth and component traits, and various
quantitative trait loci. The respective PCV and GCV were
high for total phenolics (40.4% and 40.8%), anthocyanins
(96.5% and 97.1%), FRAP value (35.3% and 35.8%) and
CUPRAC value (30.3% and 30.9%); while it was low for
root weight (8.5% and 10.5%). The trait having greater
GCV possesses a higher magnitude of variability and thus,
presents a better possibility of exploitation for improvement
in radish through various breeding approaches. Singh et
al. (2010), Singh et al. (2011) and Harakotr et al. (2015)
also reported stronger effects of genotypes for antioxidant
enzymes in cabbage, phenols and anthocyanins in strawberry,
and antioxidant content and activity in corn, respectively.
Kumar et al. (2014) also reported higher degree of Vg and
GCV for root length and root weight in radish.
Heritable portion of variation can be deduced by
computing the heritability in broad-sense and genetic advance
as percentage of mean (Table 4). High heritability (>80%)
was estimated for total phenolics (98.1%), anthocyanins
(98.7%), FRAP value (96.9%) and CUPRAC value (95.8%).
High heritability for a trait indicates that a large portion
of phenotypic variance is contributed through genotypic
variance and therefore, a reliable selection can be made
for these traits. Moreover, moderate heritability (50-80%)
was estimated for root weight (65.7%) which indicates a
considerable inuence of environment on root development.
These ndings are getting support from estimates of
indicate the presence of sufcient natural variation among
radish genotypes that could be effectively harnessed through
various breeding approaches. The mean performance,
standard error and range (Table 3) also showed large
variation for various antioxidants; while narrow range
of variation for root weight. Total phenolics differed by
4.98-fold (12.4-61.7 mg/100 g FW), anthocyanins content
by 36.16-fold (4.6-166.3 µg/g FW), FRAP value by 4.96-
fold (1.14-5.66 µmol/g FW), CUPRAC value by 4.03-fold
(2.73-11.01 µmol/g FW) and root weight by 1.37-fold
(120.1-164.8 g) among various genotypes. Previous study
has reported that the anthocyanins content in different
radish cultivars varied from 47-530 µg/g FW (Guisti et al.
1998). Furthermore, Karmakar et al. (2013) also reported
sufcient variation for antioxidant content and activity
(total phenolics, ascorbic acid, total carotenoids, DPPH-
RSA, ABTS-RSA and CUPRAC assay) in the parents and
hybrids of ridge gourd.
There was large contribution of radish genotypes to
total variations for total phenolics (97.98%), anthocyanins
(98.90%), FRAP activity (98.44%) and CUPRAC activity
(97.91%); while medium contribution for root weight
(66.29%). These results reveal that the genotypes are main
source of variations for total phenolics, anthocyanins and
antioxidant activity in radish; hence, it would be possible
to improve the content/activity of antioxidants by selection.
In corn and strawberry too, the researchers have reported
higher contribution of genotypes to the total variations
for anthocyanin, phenols, antioxidant activity and other
Table 2 Mean squares for total phenolics, anthocyanins, FRAP
activity, CUPRAC activity and root weight in coloured
radish genotypes
Source of
variation
df Mean square
Total
phenolics
Anthocy-
anins
FRAP
activity
CUPRAC
activity
Root
weight
Replication 2 5.7 32.8 0.02 0.06 184.3
Genotype 23 403.9** 4803.2** 3.73** 8.61** 511.6**
Error 46 2.6 20.8 0.04 0.12 75.8
**Signicant at P< 0.01
Table 3 Estimates of variance and coefcient of variation for total phenolics, anthocyanins, FRAP activity, CUPRAC activity and
root weight in coloured radish genotypes
Antioxidant Mean±SEm Range Difference in fold CGTV (%) Vg Vp GCV (%) PCV (%)
Total phenolics
(mg/100 g FW)
28.6±0.9 12.4-61.7 4.98 97.98 133.8 136.4 40.4 40.8
Anthocyanins (μg/g
FW)
41.4±2.6 4.6-166.3 36.16 98.90 1594.1 1615.0 96.5 97.1
FRAP activity
(μmol/g FW)
3.15±0.11 1.14-5.66 4.96 98.44 1.23 1.27 35.3 35.8
CUPRAC activity
(μmol/g FW)
5.55±0.20 2.73-11.01 4.03 97.91 2.83 2.95 30.3 30.9
Root weight (g) 141.6±5.0 120.1-164.8 1.37 66.29 145.2 221.1 8.5 10.5
FW, Fresh weight; SEm, Standard error of mean; CGTV, Contribution of genotypes to the total variation; Vg, Genotypic variance;
Vp, Phenotypic variance; GCV, Genotypic coefcient of variation; PCV, Phenotypic coefcient of variation
GENETIC VARIABILITY FOR ANTHOCYANINS AND ANTIOXIDANTS IN PIGMENTED RADISH

1604 [Indian Journal of Agricultural Sciences 87 (12)
20
coefcient of variation (GCV and PCV) reported in Table 3.
Mahan et al. (2013) also estimated high heritability (broad
and narrow sense) for total phenolic content in corn. The
efcacy and potentiality of the traits under selection could
be revealed by an assessment of genetic gain. Heritability
values along with genetic advance as percentage of mean,
together, are more useful tools for selection than either of
them alone. Genetic advance as percentage of mean ranged
from 14.2-197.4% for antioxidants and root weight in radish.
It was high for anthocyanins content (197.4%) followed by
total phenolics (82.5%), FRAP activity (65.35%), CUPRAC
activity (61.1%), and low for root weight (14.2%). In
the present study, a high heritability accompanied with
a high genetic advance for total phenolics, anthocyanins,
FRAP value and CUPRAC value clearly reect the role of
additive genes, and thus, a high genetic gain is expected
from selection and hybridization for these traits. This
nding is in accordance to Singh et al. (2011) for phenol
and anthocyanins content in strawberry. In ridge gourd too,
Karmakar et al. (2013) found the role of additive genes for
various phytonutrients and antioxidants (total phenolics,
ascorbic acid, total carotenoids, DPPH-RSA, ABTS-RSA
and CUPRAC assay). Furthermore, Mahan et al. (2013)
also observed role of additive genes for phenolic content
in corn through the estimates of narrow sense heritability
and combining ability. Moreover, root weight showed
a low genetic advance along with moderate heritability
and consequently, reected the regulation of aforesaid
trait through non-additive genes that could be harnessed
effectively through heterosis, synthetics and hybridization
in coloured radish. Present result is in concurrence with the
ndings of Kutty and Sirohi (2003), and Kumar et al. (2012)
for root weight. Realizing the importance of additive and
non-additive genes for biosynthesis of antioxidants and root
development, respectively; recurrent selection would be the
best breeding approach to improve both traits antioxidants
and root yield simultaneously.
The inter-relationship among antioxidants and root
weight was analyzed to determine the direction and
magnitude of association at the genotypic and phenotypic
levels (Table 5). Genetic associations provide basic criteria
for selection. The correlation coefcients at genotypic
level were higher in magnitude than of the corresponding
phenotypic correlation coefcients. Highly signicant
positive correlations, ranged from 0.823-0.964, were
observed for all the antioxidants, namely total phenolics,
anthocyanins, FRAP value and CUPRAC value. Previous
studies also conrmed a signicant positive correlation
among phenols, anthocyanins and antioxidants in corn
(Hu and Xu 2011, Zilic et al. 2012, Rodriguez et al. 2013,
Harakotr et al. 2015), strawberry (Singh et al. 2011) and
carrot (Koley et al. 2014). In contrast to these ndings,
Kallithraka et al. (2005) reported statistically insignicant
correlation between total anthocyanins content and
antioxidant capacity in Greek grape cultivars at harvest
stage. However, there were no correlations between
radish root weight and antioxidants (0.078-0.195) in the
present study. Nevertheless, negative correlations between
fruit weight and antioxidants were reported by Hanson
et al. (2004), Connor et al. (2005) and Karmakar et al.
(2013) in tomato, raspberry and ridge gourd, respectively.
Phenotypic correlation coefcients, in general, were slightly
lower in magnitude than of the corresponding genotypic
correlation coefcients especially for antioxidants which
indicate the lesser inuence of environmental interactions
on the genotypic expression. In this study, there was
strongest positive association between total phenolics and
anthocyanins content (0.964) because anthocyanins are the
phenolic subgroup with same biosynthetic pathway. As
anthocyanins content is directly related to total phenolics
and antioxidant activity in coloured radish, opportunity to
breed varieties/genotypes with high antioxidants is great.
In conclusion, sufcient amount of genotypic variation
were estimated for total phenolics, anthocyanins, FRAP
activity and CUPRAC activity among coloured radish
genotypes. High heritability was estimated for all the
antioxidant compounds indicated that a large portion of
Table 4 Estimates of heritability, genetic advance (GA) and GA
as percentage of mean for total phenolics, anthocyanins,
FRAP activity, CUPRAC activity and root weight in
coloured radish genotypes
Antioxidant Heritability
(%)
GA GA as percentage
of mean (%)
Total phenolics 98.1 23.6 82.5
Anthocyanins 98.7 81.7 197.4
FRAP activity 96.9 2.2 71.5
CUPRAC activity 95.8 3.4 61.1
Root weight 65.7 20.1 14.2
GA: Genetic advance
Table 5 Correlation coefficient between total phenolics,
anthocyanins, FRAP activity, CUPRAC activity and
root weight in coloured radish genotypes
Antioxidant Total
phenolics
Antho-
cyanin
FRAP
activity
CUPRAC
activity
Root
weight
Total phe-
nolics
g0.964** 0.918** 0.940** 0.165
p0.948** 0.899** 0.908** 0.125
Anthocya-
nins
g 0.859** 0.908** 0.083
p 0.833** 0.882** 0.078
FRAP
activity
g 0.862** 0.195
p 0.823** 0.163
CUPRAC
activity
g 0.132
p 0.123
Root
weight
g
p
**Signicant at P< 0.01; g, Genotypic level; p, Phenotypic
level.
SINGH ET AL.

1605December 2017]
21
variance is contributed through genotypic variance and a
reliable selection could be made for antioxidant compounds.
The signicant positive correlations among total phenolics,
anthocyanins content, FRAP value and CUPRAC value
could be used as indirect selection criteria for improving
the levels of antioxidants. Examining the involvement
of additive and non-additive genes for biosynthesis of
antioxidants and root development, respectively; recurrent
selection would be the best breeding approach to improve
the both traits antioxidant concentration and root yield
simultaneously. The information, therefore, gained from
this study could be used in future breeding programmes to
improve the yield and antioxidant levels of radish.
ACKNOWLEDGEMENTS
The authors would like to express their special thanks to
the Director, ICAR-Indian Institute of Vegetable Research,
Shahanshahpur, Varanasi, Uttar Pradesh, India for nancial
support during the present research work. The authors
declare that there are no conicts of interest.
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