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European Journal of Applied Sciences – Vol. 10, No. 1
Publication Date: February 25, 2022
DOI:10.14738/aivp.101.11606. Otusanya, M. O. (2022). Tuber Minerals and Phenolic Compounds in Calcium Nitrate Foliar-Sprayed Dioscorea Alata Var. Agbodo
and D. rotundata Var. Amula. European Journal of Applied Sciences, 10(1). 176-184.
Services for Science and Education – United Kingdom
Tuber Minerals and Phenolic Compounds in Calcium Nitrate
Foliar-Sprayed Dioscorea Alata Var. Agbodo and D. rotundata Var.
Amula
Otusanya, M.O.
ABSTRACT
Calcium Nitrate foliar spray for the management of anthracnose disease was
assessed in Dioscorea alata variety Agbodo and D. rotundata var. Amula in two
experiemental plots in COLPANT Farms, College of Plant Science and Crop
Production, Federal University of Agriculture, Abeokuta, Ogun State in Nigeria. The
design in each plot was randomized complete block (RCBD) with three replications.
Mounds were 1 metre (m) by 1m and about 80cm high, with inter-replicate inter- row and intra-row spacing of 1m, 1m and 0.5m respectively. One metre (1m) clear
border was maintained on each of the four sides of each plot. Each replicate had 18
plants. Calcium Nitrate foliar spray at the rates 0mgl-1, 5mgl-1 and 10mgl-1 was
applied without surfactant at twelve weeks after planting (12 WAP). Anthracnose
incidence and severity results are presented in another paper. But tubers in the
plots were sampled at 24 WAP in order to determine, Calcium nitrate foliar spray of
5mgl-1 and 10mgl-1 without surfactant, effect on tuber minerals, namely Calcium
(Ca), Magnesium (Mg), Nitrogen (N), Phosphorus (P), Potassium (K) and Sulphur (S),
as well as Tuber Total Phenolic Compounds (TPC) and yield. The results of yield,
TPC and the tuber minerals are presented in this paper. Statistical analysis was
carried out separately for each plot. Tuber Number Per Plant (TNPP) and Tuber
Weight Per Plant (TWPP) were similar across treatments for water Yam Agbodo and
white guinea yam Amula. TNPP overall means are 4.43 and 3.16 for Agbodo and
Amula respectively. TWPP overall means are 2.00kg (or 20.00 tonsha-1) and 1.91kg
(or 19.10 tonsha-1) for Agobdo and Amula respectively. Yield (tuber fresh weight) is
similar to that obtained in a report of Calcium nitrate foliar spray for anthracnose
control in Dioscorea species (two improved and one local variety), but which had
relatively higher spray concentrations of 0 to 12000 milligram per litre and with
surfactant in the spray liquid. Tuber Ca, Mg, N and P were significantly higher in the
treatments than the control in water yam Agbodo as follows: Ca in mg/100g dm is
21.48 (10mgl-1) > 19.16 (5mgl-1) > 16.31 (Control); Mg in mg/100gdm is 24.53
(10mgl-1) > 21.22 (5mgl-1) > 19.02 (control); N in percent (%) is 1.86 (10mgl-1) >
1.37 (5mgl-1) > 0.95 (control); P in mg/100g dm is 56.27 (10mgl-1) > 53.14 (5mgl-1)
> 49.76 (control). K in mg/100g dm in Agbodo is 807.70 (10mgl-1) higher than
770.60 (control). S and Total Phenolic Compounds (TPC) of Agbodo were overall
means 4.68% and 5.58mg Gallic Acid Equivalent per gram dry matter
(5.58mgGAE/gdm) respectively. In white guinea Yam Amula, TPC and five of the
minerals were higher significantly in the treatments than the control as follows:
TPC in mgGAE/gdm is 5.92 (10mgl-1) > 5.39 (5mgl-1) > 4.82 (control); Ca in
mg/100gdm is 18.22 (10mgl-1) > 16.45 (5mgl-1) > 14.49 (Control); N in % is 1.80
(10mgl-1) > 1.11 (5mgl-1) > 0.91 (control); P in mg/100gdm is 54.82 (10mgl-1) >
50.84 (5mgl-1) > 48.59 (control); K in mg/100gdm is 812.44 (10mgl-1) > 793.29
(5mgl-1) > 759.22 (control); S in % is 6.42 (10mgl-1) > 5.23 (5mgl-1) > 4.48 (control).
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Otusanya, M. O. (2022). Tuber Minerals and Phenolic Compounds in Calcium Nitrate Foliar-Sprayed Dioscorea Alata Var. Agbodo and D. rotundata
Var. Amula. European Journal of Applied Sciences, 10(1). 176-184.
URL: http://dx.doi.org/10.14738/aivp.101.11606
Mg in white Yam Amula was overall mean of 20.19mg/100gdm, similar across
treatments. A numerical comparison may be made of the two species (two varieties)
because statistical analysis was carried out separately in the two experimental
plots. Thus numerically (not statistically) overall means were higher in Agbodo in
yield (TNPP and TWPP), TPC, Ca, Mg, N, P and K, than Amula. Amula was numerically
higher in Sulphur only than Agbodo. Phenolic compounds reports of association
with defence mechanisms in crop plants because they exhibit anti-fungal, anti- bacterial and anti-viral properties is discussed. Phenolic compounds reports of
exhibition of antioxidant or free radical scavenging properties that boost immunity
against diseases caused by free radical reactions such as cancer, diabetes, aging and
cardio vascular diseases, as well as analgesic and anti-inflammatory properties is
also discussed. This is to draw attention to inputs during Crop Protection Research
such as this study which will effect synthesis of, or increase phenolic compounds in
the edible food yams for disease resistance as well as for health benefits. Increase
in calcium in this study would enhance disease resistance due to calcium role in the
enhancement of the integrity of intracellular cementing materials. Magnesium and
phosphorus requirement in yams is reported to be low, thus the increase in this
study will ensure yams receive the optimum of the two elements. Lastly, Nitrogen
and Potassium increase is to be emphasized for recommendation of 5mgl-1 and
10mgl-1 calcium nitrate foliar spray in Dioscorea species as the two are the most
important for optimum yield in yams.
INTRODUCTION
Calcium Nitrate Foliar Spray for control of Anthracnose disease in two improved and one local
variety of Dioscorea species was reported, with five concentrations between 0mgl-1 and
12000mgl-1 (Otusanya et al., 2017). Yield obtained in the first year was similar across
treatments. Yield in the second year however, was significantly higher than the control, after a
change in rate and time of the foliar spray. In a second study, relatively lower concentrations of
5 and 10 milligram per litre of calcium nitrate foliar spray without surfactant were evaluated
for anthracnose control in two Nigerian local varieties of Dioscorea alata and D. rotundata
namely Agbodo and Amula respectively. The results of Yield, Tuber Total Phenolic Compounds
and six tuber minerals (Calcium, Magnesium, Nitrogen, Phosphorus, Potassium and Sulphur) in
the study are presented in this paper.
MATERIALS AND METHOD
Planting Material
Tubers of Dioscorea alata variety Agbodo and D. rotundata variety Amula were sourced from
the Osiele Yam market in Abeokuta, Ogun State, Nigeria. Agbodo is a Yoruba (South West
Nigeria) local name and the variety is widely grown in the South West region of Nigeria. Amula
is widely grown in Benue State in the middle belt region of Nigeria (Shiriki et al., 2015). But
Amula has also been adopted in South West Nigeria and other parts of the country as farmers
refer to it as a good yielding variety.
Field Experiment
Two experiments were carried out in two separate plots in COLPLANT (College of Plant Science
and Crop Production Fatms), Federal University of Agriculture, Abeokuta FUNAAB, Ogun State,
Nigeria. Each was RCBD (Randomized Complete Block) with three replications. Mounds in each
replicate were 1metre (m) by 1m, and about 80cm high, with inter-replicate, inter-row, and
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
Services for Science and Education – United Kingdom
intra-row spacing of 1m, 1m and 0.5m respectively. A clean border of 1m space was maintained
on each of the four sides of each plot. Each replicate had eighteen mounds. The two experiments
were of calcium nitrate foliar spray at the rates 0mgl-1 (control) 5mgl-1 and 10mgl-1 applied
without surfactant at 12WAP (Weeks after planting), to evaluate calcium nitrate effect on
anthracnose incidence and severity, and the results have been presented elsewhere.
However tubers from the plots were analysed for effect of the spray solution on tuber quality
in terms of mineral content and total phenolic compounds. The tuber analysis results as well as
tuber yield at 24 WAP are presented in this paper.
Tuber Sampling and Processing for Analysis at 24 WAP
Tuber sampling was along the diagonal transect of each plot replicate. Wooden spoons were
used to move soil away from tubers within the mound and the shoots attached cut away with a
sharp stainless steel knife. Mounds were then closed up with soil for the final harvest the
following day. Tubers were removed in triplicate per treatment per replicate. Sampled plants
were tagged so as to have a correct record of total number of tubers produced by the plant and
tuber weight per plant in the final harvest. The tubers were cleared of soil, washed in tap water
and left to dry on top of laboratory benches under low-speed ceiling fans. After drying, they
were sliced into thin chips with stainless steel knives and left to dry in labelled plastic trays on
the bench tops for about four days. They were milled after drying with a Hammer and Bull Mill.
The milled samples were transferred to the Biological Tetfund Laboratory in FUNAAB and the
Biotechnology centre in FUNAAB for tissue analysis. Total phenolic compounds and mineral
analysis of Calcium (Ca) Magnesium (Mg) Nitrogen (N) Phosphorus (P) Potassium (K) and
Sulphur (S) in the samples was according to standard methods of the A.O.A.C (1990/2000).
Havest at 24 WAP
The final harvest was done one day after the tuber sampling for analysis. Dislodging tubers from
within the mounds was in the same way as for the tubers harvested for analysis, to avoid
bruising or wounding. Total number of tubers per plant was recorded as well as weight of
tubers per plant using a field top loading mettler balance (field scale).
Statistical Analysis
Data obtained were analysed with SAS 2000 version 9.1.1 and means separated with Tukey’s
Honest Studentized Range (HSD) test.
RESULTS AND DISCUSSION
Dioscorea alata variety Agbodo and D. rotundata variety Amula were sprayed in two separate
experimental plots in COLPLANT (College of Plant Science & Crop Production, Federal
University of Agriculture, Abeokuta, Nigeria) FARMS with Calcium Nitrate rates 0mgl-1
(control) 5mgl-1 and 10mgl-1 for the management of Anthracnose disease. Tubers were sampled
in the two plots at 24 WAP, to assess the effect of the spray solution on tuber minerals and tuber
total phenolic compounds. In the first report of Calcium nitrate foliar spray to control
Anthracnose in two improved varieties and one local variety of Dioscorea species in Nigeria,
there were four differences in methodology namely variety as well as rate and time of spray
solution application and addition of surfactant (Otusanya et al., 2017). In the cited report, rate
and time of calcium nitrate foliar spray were 0mgl-1 to 12000mgl-1 (5 treatments) at emergence
and thereafter bi-weekly until 12 weeks after planting (12 WAP) in the first year. And 0mgl-1to
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Otusanya, M. O. (2022). Tuber Minerals and Phenolic Compounds in Calcium Nitrate Foliar-Sprayed Dioscorea Alata Var. Agbodo and D. rotundata
Var. Amula. European Journal of Applied Sciences, 10(1). 176-184.
URL: http://dx.doi.org/10.14738/aivp.101.11606
12000mgl-1 calcium nitrate (4 treatments) applied at 12WAP and 20WAP in the second year. In
this study rate and time of calcium nitrate foliar spray were 0mgl-1 to 10mgl-1 (3 treatments)
applied at 12WAP only. The tuber fresh yield, tuber total phenolic compounds and tuber
minerals, analysed separately for the two varieties are presented and discussed.
Tuber Number Per Plant (TNPP) and Tuber Weight Per Plant (TWPP) were not significantly
different across treatments in the water yam Agbodo or in white guinea yam Amula. TNPP
overall mean is 4.43 and 3.16 in Agbodo and Amula respectively as shown in Table 1. TWPP is
overall mean 2.00kg (or 20tons ha-1) and 1.91kg (or 19.10tons ha-1) in Agbodo and Amula
respectively (Table 1). Otusanya et al., (2017) reported 1.85kg (or 18.50tons ha-1) in the
750mgl-1 Ca(NO3)2 treatment and 1.76kg (or 17.60tons ha-1) in the 12000mgl-1 treatment, both
significantly higher than the control of 1.24kg (or 12.40tons ha-1) in the second year. Yield in
this study is similar to the cited report, despite the four differences mentioned earlier.
Surfactant was not used in the spray solution in this study to avoid its scorching effects because
the optimum had not been determined for Calcium nitrate in Dioscorea species. Significantly
higher yield in treatments in the report of Otusanya et al., (2017) was mainly due to interaction
effect in the improved variety TDa 92-2, as there was no significant interaction in the second
improved variety which is a different species, white yam TDr 131 or in the third variety, the
local D. alata variety Iberekodo. This ability in the improved variety TDa 92-2, may be due to
genetic specificity which explains variability in growth, carbon fixation and nutrient uptake
between species (Diby et al., 2004).
However, tuber TPC and minerals were higher in the treatments over the control in this study.
Water yam Agbodo tuber Ca, Mg, N and P were significantly higher in the two Ca(NO3)2
treatments than the control as shown in Table 2 thus: Ca in mg/100gdm is 21.48(10mgl-1) >
19.16 (5mgl-1) > 16.31 (Control). Mg in mg/100gdm is 24.53(10mgl-1) > 21.22 (5mgl-1) > 19.02
(control). N in percent (%) is 1.86 (10mgl-1) > 1.37 (5mgl-1) > 0.95 (control). P in mg/100gdm
is 56.27 (10mgl-1) > 53.14 (5mgl-1) > 49.76 (control). K in mg/100gdm in Agbodo is higher in
the 10mgl-1 treatment than the control, 807.70 (10mgl-1) > 770.60 (control), (Table 2). S and
TPC were similar across treatments in Agbodo and have overall means of 4.68% and 5.58mg of
Gallic Acid Equivalent per gram dry matter respectively (Table 2).
In white guinea yam Amula, TPC and five of the six minerals were significantly higher in the two
calcium nitrate treatments than the control (Table 2) as follows: TPC in mg GAE/gdm is 5.92
(10mgl-1) > 5.39 (5mgl-1) > 4.82 (control); Ca in mg/100gdm is 18.22 (10mgl-1) > 16.45 (5mgl- 1) > 14.49 (control); N in % is 1.80 (10mgl-1) > 1.11 (5mgl-1) > 0.91 (control); P in mg/100gdm
is 54.82 (10mgl-1) > 50.84 (5mgl-1) > 48.59 (control); K in mg/100gdm is 812.44 (10mgl-1) >
793.29 (5mgl-1) > 759.22 (control); S in % is 6.42 (10mgl-1) > 5.23 (5mgl-1) > 4.48 (control). The
sixth mineral Mg was similar across treatments in Amula, with overall mean of
20.19mg/100gdm as shown in Table 2.
Separate experimental plots were used for Agbodo and Amula thus values/results obtained for
the two species may only be compared numerically. Generally numerically not statistically,
overall means were higher in water yam Agbodo in Yield (both tuber number per plant and
tuber weight per plant), total phenolic compounds and five of the six minerals (calcium,
magnesium, nitrogen, phosphorus and potassium) than white yam Amula (Table 2). Amula was
numerically higher only in sulphur (5.38%) content than Agbodo (4.68%), (Table 2).
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Phytochemicals or secondary metabolites such as phenolic compounds occur naturally in
plants and form part of the plant defence mechanisms against disease because they exhibit anti- microbial, anti-bacterial and anti-viral properties. Marie et al., (2005) reported 79.3mg/kg
phenolic compounds in variety St. Vincent of D. alata in Jamaica, which is lower than that
obtained in D. alata var. Agbodo in this study. Martin Kouakou et al., (2010) reported that higher
phenolic compound content of over 200mg/100g dry weight of the proximal portions of the
two yam species D. alata variety Florido and D. cayenensis-rotundata complex variety Krengle
was responsible for higher resistance to microbial attack in those portions than the distal
portions, which had lower phenolic compound content. The phenolic compound value obtained
in the latter report is also lower than that in this study for either water yam Agbodo or white
yam Amula. Phenolic compounds extracted (acqeous and ethanolic extracts) from the Yam
Peels of tubers of Dioscorea bulbifera and D. alata (collected from Nat. Root Crop Res. Inst.,
Umudike Yam Barn in South East region of Nigeria) exhibited various anti fungal actions in a
dose-dependent manner, and at 40% concentration exhibited higher inhibitory action on
Botryodipodia theeobromae than standard Griseofulvin a fungicide (Eleazu et al., 2013). B.
theobromae is one of the three important economic storage pathogens of yams in Nigeria (Dania
et al., 2012). The phenolic compound Catechin of the value 12 to 69mg catechin/100g fresh
weight were reported in cultivars Abii, Ekpe, Nwopoke, Obiaturugo and Okwocha of Dioscorea
rotundata, and 304 to 513mg/100g fresh weight of catechin in cultivars Ominelu and UM 680
of Dioscorea alata (Ozo et al., 1984). The concentrations are of the cultivar fresh weight and are
lower than the TPC obtained in this study. Ozo et al., (1984) also reported that the two cultivars
Uminelu and UM 680 of D. alata, cultivar Adu of Dioscorea bulbifera, cultivar Oku of Dioseorea
cayenensis and cultivar Ona of Dioscorea dumetorum, all had higher phenolic compound content
than the five cultivars Abii, Ekpe, Nwopoke, Obiaturugo and Okwocha of Dioscorea rotundata.
The ten cultivers of five species in the latter report (of Ozo et al., 1984) are edible food yams
from the South East region of Nigeria. Graham – Acquaah et al. (2014) reported a similar range
as that of Ozo et al., 1984, of 20-37mg catechol/100g in Puna and Bayere Fitaa in Ghana. The
latter two cultivars are important and cultivar Puna is the most preferred white guinea yam
cultivar for export and local consumption in Ghana (Erio William Cornelius, 1998). Polyphenols
have also been reported to be associated with antioxidant activity or free radical scavenging
properties which boost immunity against diseases caused by free radical reactions such as
cancer, cardiovascular diseases, diabetes and aging (Lubag et al., 2008; Sonibare and Abegunde
2012; Bhandarii and Kawabata 2004; Cornago et al., 2011). Others regulate processes such as
the reduction of cholesterol absorption, and others exhibit analgesic and anti-inflammatory
properties (Avula et al., 2012, 2014; Alamu et al., 2014; Zang et al., 2014; Padhan et al., 2020;
Price et al., 2017). Total phenolic compounds increase in this study and the facts stated in the
foregoing cited reports, draw attention to phenolic compounds synthesis in the edible Food
yams (and some potentially useful wild relatives) during Yam Crop Protection research, during
Yam Breeding Research and during Yam Soil Fertility Research, which have enormous potential
for development of drugs for human health benefits. Gibney et al., 2009 and Lanham – New et
al., 2010 report that research is on to establish recommended daily intake (RDA values) for
these Bioactive Compounds (Phenolics) but it is generally agreed currently that they have
positive influence on human health, and that when they are consumed as part of a balanced
diet, the benefits are significant (Halliwell and Gutteridge, 2007).
Calcium maintains the intergrity of intracellular cementing materials (Polycarp et al., 2012).
The increase in calcium in the two varieties in this study, thus resulted in enhancement of
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Otusanya, M. O. (2022). Tuber Minerals and Phenolic Compounds in Calcium Nitrate Foliar-Sprayed Dioscorea Alata Var. Agbodo and D. rotundata
Var. Amula. European Journal of Applied Sciences, 10(1). 176-184.
URL: http://dx.doi.org/10.14738/aivp.101.11606
resistance to nematodes and pathogenic attack. The latter especially microbial pathogens are
responsible for the highest losses in stored yams (Cornelius and Oduru, 1999). Phosphorus is
not a limiting nutrient in yam production because mycorrlizal associations (with fungi) in Yam
roots allow uptake of the mineral element (Obigbesan and Agboola, 1978). Uptake of
Magnesium by yams (Dioscorea spp.) is also reported to be low (Obligbesan and Agboola, 1978;
O’Sullivan and Jenner, 2006). Thus Phosphorus increase in both varieties and Magnesium
increase in variety Agbodo in this study means that 5mgl-1 and 10mgl-1 calcium nitrate foliar
spray ensures optimum uptake of the two mineral elements by Dioscorea species tubers.
Nitrogen and Potassium both increased in the two varieties in this study and these two mineral
elements are the most important for optimum yield in Dioscorea species (Degras, 1993; Diby et
al., 2011; O’Sullivan, 2008).
Calcium, Magnesium, Nitrogen, Phosphorus, Potassium and Sulphur are all essential dietary
minerals in the human diet, playing vital roles in the body metabolic processes (Polycarp et al.,
2012).
Table 1: Tuber Yield in Calcium Nitrate Foliar – Sprayed D. alata var. Agbodo and D. rotundata
var. Amula
TUBER NUMBER PER PLANT
(TNPP)
TUBER WEIGHT PER PLANT (TWPP) kg
CALCIUM
NITRATE
FOLIAR SPRAY
AGBODO AMULA AGBODO AMULA
Kg (Tonsha- 1)
Kg (Tonsha- 1)
0 4.80a 2.93a 1.62a (16.20) 1.87a (18.70)
5 4.15a 2.73a 2.48a (24.80) 1.73a (17.30)
10 4.34a 3.83a 1.89a (18.90) 2.13a (21.30)
OVERALL MEAN 4.43 3.16 2.00 (20.00 1.91 (19.10)
Means in the same column followed by the same letter are not significantly different at P ≤ 0.05,
Tukey’s HSD Test
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Table 2: Tuber Total Phenolic Compounds and Tuber Minerals in Calcium Nitrate Foliar- Sprayed D. alata variety Agbodo and D. rotundata variety Amula
AGBODO AMULA
TPC mgGAE/gdm
Ca(NO3)2 0 5 10 mgl-1
Calcium mg/100gdm
0 5 10
Magnesium mg/100gdm
0 5 10
Nitrogen %
0 5 10
Phosphorus mg/100gdm
0 5 10
Potassium mg/100gdm
0 5 10
Sulphur %
0 5 10
5.58
5.61a 5.56a 5.57a
18.98
16.31c 19.16b 21.48a
21.59
19.02c 21.22b 24.53a
1.362
0.95c 1.37b 1.86a
53.06
49.76c 53.14b 56.27a
789.45
770.60b 790.05ab 807.70a
4.68
4.81a 5.02a 4.21a
5.34
4.82c 5.39b 5.92a
16.35
14.49c 16.45b 18.22a
20.19
20.10a 20.37a 20.09a
1.273
0.91c 1.11b 1.80a
51.42
48.59c 50.84b 54.82a
788.32
759.22c 793.29b 812.44a
5.38
4.48c 5.23b 6.42a
Means aligned horizontally followed by the same letter are not significantly different at P ≤ 0.05,
Tukey’s HSD Test.
Overall means for the two Dioscorea spp. Are indicated in vertical columns.
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