Vol. 14(11), pp. 443-450, November 2020
DOI: 10.5897/AJPS2020.2029
Article Number: 5BE534F65512
ISSN 1996-0824
Copyright © 2020
Author(s) retain the copyright of this article
http://www.academicjournals.org/AJPS
African Journal of Plant Science
Full Length Research Paper
Evaluation of plant extracts for the management of
Cercospora leaf spot of groundnut
(Arachis hypogaea L.)
Moses Neindow*, Elias Nortaa Kunedeb Sowley and Frederick Kankam
Department of Agronomy, Faculty of Agriculture, University for Development Studies, P. O. Box TL 1882,
Nyankpala Campus, Tamale, Ghana.
Received 8 June, 2020; Accepted 15 October, 2020
Groundnut (Arachis hypogaea L.) is a leguminous crop with high economic and nutritional value.
However, increased production is hampered by Cercospora leaf spot (CLS) caused by Cercospora
arachidicola and Cercosporidium personatum. Studies were conducted in vitro and in vivo to evaluate
the efficacy of aqueous extracts of desert date seed (DDSE), neem seed (NSE), jatropha seed (JSE) and
tobacco leaf (TLE) for the management of CLS. The antifungal activities of 25, 50, 75 and 100 g/l
concentrations of each of the plant extracts was assessed in vitro on potato dextrose agar using the
food poison technique. The field study was a factorial experiment consisting of 18 treatments laid in a
Randomised Complete Block Design with four replications over two cropping seasons. The in vitro
results revealed that all the botanicals at 100 g/l recorded the highest inhibition percentages. DDSE at
100 g/l significantly (P < 0.001) inhibited the highest mycelia growths compared to other levels of plant
extracts used with inhibition percentages of 90.33 and 84.96% in C. arachidicola and C. personatum,
respectively. Three out of the four aqueous extracts (DDSE, NSE and JSE) at 100 g/l significantly (P <
0.05) lowered disease incidence, severity and defoliation in the field and increased yield. Pod yield was
significantly (P < 0.05) higher in plants treated with JSE, NSE, DDSE and Topsin-M, compared to those
treated with TLE and the negative control plants. For most of the parameters, DDSE produced similar
results as Topsin-M followed by NSE and JSE. Farmers can adopt DDSE, NSE and JSE as alternatives
to fungicides leading to minimal effect on the environment since they are biodegradable.
Key words: Cercospora leaf spot, plant extracts, groundnut, incidence, severity, aqueous.
INTRODUCTION
Ghana is a major producer of groundnuts (Arachis
hypogaea L.) in West Africa with nearly all production
coming from northern Ghana (DAI and Nathan
Associates, 2014). Despite its economic importance in
the northern parts of Ghana, its current average yield of
0.8 t/ha is not up to its potential yield of 2.5 to 3.0 t/ha
*Corresponding author. E-mail: neindowmoses@gmail.com.
Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution
License 4.0 International License
444
Afr. J. Plant Sci.
(Kombiok et al., 2012; Tanzubil et al., 2017). This large
yield gap is attributable to diversity of production
constraints, notably pests and diseases, low inherent
yielding varieties, low and high temperatures at certain
growth stages of the crop, non-irrigated cultures and
increased cultivation on marginal lands among others
(Ambang et al., 2011; Tshilenge-Lukanda et al., 2012).
Nonetheless, Cercospora leaf spot (CLS) caused by
Cercospora arachidicola and Cercosporidium personatum
is the most destructive foliar disease in West Africa
(Mohammed et al., 2019).
Control of CLS with fungicides is effective but it largely
depends on inorganic fungicide applications which are
too expensive for indigenous farmers in Northern Ghana
(Nutsugah et al., 2007; Akinbode, 2010; Jordan et al.,
2012). Aside from this, chemical control also raises
environmental and health concerns (Jordan et al., 2012).
In Ghana, Imoro et al. (2019) reported that mode of
storage of pesticides by farmers have adverse effects on
their health as well as the environment.
Although fungicides are effective for controlling the
disease, awareness about environmental pollution
caused by misuse of fungicide, tolerant pathogens
strains, non-availability of both fungicides and their
application technology to resource-limited farmers, have
necessitated the use of more economical and
ecologically-friendly alternatives. There are reports on the
potential of some plants with fungicidal properties which
can be used for controlling diseases. For instance,
Sowley et al. (2017) reported that Azadirachta indica
seed and Cassia alata leaf extracts controlled seed borne
fungi of maize. The study sought to determine the
efficacy of some botanicals for the management of
Cercospora leaf spot of groundnut.
MATERIALS AND METHODS
Experimental site
Laboratory studies were carried out in the Spanish laboratory at the
University for Development Studies, Nyankpala campus, during
2014 and 2015 cropping seasons whilst the field studies was
conducted under rain-fed conditions in 2014 and repeated in 2015
on the experimental field of the Faculty of Agriculture, University for
Development Studies, Nyankpala campus.
Sample collection
A. indica and Jatropha curcas seeds, as well as Nicotiana tabacum
leaves, were collected from Fooshegu and Tamale whilst Balanites
aegyptiaca seeds were obtained from Jantong-Dashee in the East
Gonja district. The plant materials were obtained from healthy
plants. The seed and leaf samples were stored in polyethene bags
until required.
Optimization of plant extract concentrations
The various plant materials (that is, neem, J. curcas, desert date
seeds and tobacco leaves) were collected, washed with several
changes of sterile distilled water, and air-dried to constant weight
for 10 days; tobacco leaves were cut into tiny pieces before
washing and drying. For seeds, the coats were removed before
pounding. The dried plant materials were pounded separately with
sterile mortar and pestle and sieved with a fine sterile cheesecloth
to obtain a fine powder. The powders obtained were sieved through
a screen with a mesh size of 0.4 mm to obtain a fine powder. Cold
aqueous extracts of the samples were prepared separately by
adding 25, 50, 75 and 100 g of the powder samples into conical
flasks. Each sample was wrapped in cheesecloth and soaked in 1 L
of water for 24 h. The cloth was squeezed and the extract was
filtered. 2 g of an emulsifier (‘key soap’) was added to each filtrate
to facilitate sticking. Based on the results of the in vitro studies, 100
g/l was identified as the most effective concentration of the extract
and used for the field study.
Phytochemicals screening of the plant extracts
Alkaloids, saponins, tannins, steroids and terpenoids were detected
with the methods described by various workers.
Following the methods of Edeoga and Okwu (2005) and Kareru
et al. (2008), the presence of alkaloids were detected in the plant
extracts. The methods described by Wall et al. (1954) and Kareru et
al. (2008) were used for testing for saponins. The methods
described by Sabri et al. (2012) were also used for detecting
tannins and phenolic compounds. Similarly, Salkowski test was also
used for the detection of steroids and terpenoids.
Isolation and
personatum
identification
of
C.
arachidicola
and
C.
Potato Dextrose Agar (PDA) was prepared based on the
manufacturer’s recommendation of 39 g/l. The media was
autoclaved at a temperature of 121°C and a pressure of 1.02
kg/cm3 for 15 min. It was then amended with 1 g of chloramphenicol
before dispensing into sterile Petri dishes and allowed to cool.
Pieces of infected groundnut leaves were sterilised with 4% sodium
hypochlorite. The sterile pieces of leaf were placed on the PDA
plates at equidistant points and kept in a freezer at a temperature of
28°C for 48 h. Following the procedure of Barnett and Hunter
(1998), fungi were identified based on morphological and cultural
features. Slides of pure cultures obtained were prepared and
observed under a compound microscope (Celestron LCD Digital
microscope, Model number 44340, UK).
Determination of the inhibitory effect of the aqueous plant
extracts on mycelia growth of C. arachidicola and C.
personatum
Food poison technique was used for the infected samples of the
three groundnut cultivars (‘Chinese,’ Mani-pintar and ‘Bugla’). Five
millilitres of each extract concentration (that is, 25, 50, 75 and 100
g/l) of the supernatant of the test extracts were dispersed in 20 ml
potato dextrose medium in 90 cm Petri dishes, swirled to blend and
allowed to solidify. A 5 mm disc of five days old culture of the two
test fungi each was inoculated separately at the centre of the PDA
medium and incubated at 28 ± 2°C. The growth of each fungus
diametrically was taken for 7 days on daily basis. For positive
controls, 5 ml of Topsin-M prepared at the recommended rate (1 g/l)
as well as 2 and 3 g/l were used for the amendment. The negative
controls had only the PDA medium without the extracts. The colony
diameter representing mycelia growth was measured using a
transparent rule on a daily basis after inoculation for seven days.
Neindow et al.
The percentage inhibition of mycelial growth was calculated as
follows (Begum et al., 2010):
I=(C-T/C) ×100
where I = Percentage inhibition, C = Radial growth in control, T
=Radial growth in treatment.
Pathogenicity test of C. arachidicola and C. personatum
The seedlings of the ‘Chinese’ cultivar were raised on loamy soil
contained in perforated black polythene bags (15 × 30 cm2) in a
plant house with an average temperature of 28°C. Twenty-one-day
old plants were pinpricked and sprayed with a suspension
containing mycelia of C. arachidicola and C. personatum [1 × 103
cfu mL-1] prepared in sterile distilled water, except the control
plants. Pathogenicity test of the fungal isolates was based on the
method of Eman (2011).
Measurement of disease parameters
Disease incidence
Five plants were randomly selected and tagged for disease
assessment in each plot per treatment during 2014 and 2015
cropping seasons. Disease incidence was recorded on these five
plants in each plot for every treatment before treatment application.
Mean % incidence was calculated with the formula (Chaube and
Pundhir, 2009):
Disease Incidence (%) =
445
Experimental design
The field experiment was a 6 × 3 factorial laid out in a Randomised
Complete Block Design (RCBD) with four replications per treatment.
Each replication consisted of 18 experimental plots measuring 4 × 5
m2. The factor levels comprised three groundnut cultivars, namely:
Chinese, Mani-Pinta and Bugla, and four plant extracts (desert date
seed, neem seed, jatropha seed and tobacco leaf) with Topsin-M
and water as positive and negative controls, respectively, producing
18 treatments. All groundnut cultivars (Chinese, Mani-pintar and
Bugla) were obtained from the Seed Unit of the Savannah
Agricultural Research Institute (SARI, 2014).
One seed each of the groundnut was sown per hole at a depth of
about 5 cm in a planting distance of 50 cm × 20 cm. Each plot
consisted of 10 rows and four median rows which were used for
disease assessment and yield records. Treatments were applied
every 2 weeks from 2 to 13 weeks after planting (WAP) using a 15L knapsack sprayer.
The treatments used were as follows: Neem seed extract (NSE)
+ Chinese, Neem seed extract (NSE) + Mani-Pintar, Neem seed
extract (NSE) + Bugla, Desert date seed extract (DDSE) + Chinese,
Desert date seed extract (DDSE) + Mani-Pintar, Desert date seed
extract (DDSE) + Bugla, Tobacco leaf extract (TLE) + Chinese,
Tobacco leaf extract (TLE) + Mani-Pintar, Tobacco leaf extract
(TLE) + Bugla, Jatropha seed extract (JSE) + Chinese, Jatropha
seed extract (JSE) + Mani-Pintar, Jatropha seed extract (JSE) +
Bugla, Topsin-M + Chinese, Topsin-M + Mani-Pintar, Topsin-M +
Bugla, Water + Chinese, Water + Mani-Pintar and Water + Bugla.
Statistical analysis
The data were subjected to analysis of variance (ANOVA) using
Genstat Discovery (12th Edition). Treatment means were separated
using the Least Significance Difference (LSD) at 5% significant
level.
Disease severity and disease severity index (%)
Five plants in each plot per treatment were randomly selected and
tagged. These plants were used to assess the severity of CLS
using the Florida scale system of 1 - 10, where 1 = no leaf spot and
10 = plants completely defoliated and killed by leaf spots (Chiteka
et al., 1988). The descriptive keys were used to determine the
severity of the disease.
Disease severity index (DSI) was then calculated using the
equation proposed by Kobriger and Hagedorn (1983):
DSI =
The evaluation of early and late symptoms of CLS was done after
every 14 days starting from the 3rd WAP.
Yield and yield parameters
Yield characteristics such as the weights of 100 pods and 100
seeds from each plot per treatment were randomly picked and
weighed using a Sartorious scale balance. The average weight of
five counts was then taken as the weight of 100 pods and 100
seeds for each plot per treatment. Similarly, the total dry pod and
seed yields of groundnut from the respective treatments were
determined using the four median rows in each plot per treatment.
The weights of groundnuts harvested from each plot were
extrapolated to total pod yield per hectare basis.
RESULTS
Phytochemical composition of plant extracts
Neem seed and tobacco leaf extract treated plants had
the highest number of phytochemicals while jatropha
seed extract had the lowest (Table 1). All the extracts
contained alkaloids, tannins and phenolic compounds.
Only desert date seed, neem seed and tobacco leaf
contained saponins. Steroids were present in only neem
seed and terpenoids in only neem seed and tobacco leaf.
Isolation of causative organism
The fungal pathogens C. arachidcola and C. personatum
were isolated from infected leaves of three groundnut
cultivars Bugla, Mani-Pinta and Chinese and confirmed
as the causative agents of Cercospora leaf spot diseases
of groundnut. The conidium of C. arachidicola is sub
hyaline or pale yellow, obclavate or cylindrical and
septate with rounded base and sub-acute tip (Figure 1A).
However, in the case of C. personatum conidium was
obclavate or cylindrical and light coloured. The base is
shortly tapered with a conscipicous hilum (Figure 1B).
446
Afr. J. Plant Sci.
Table 1. Phytochemical constituents of plant extracts.
Phytochemical constituent
Alkaloids
Saponins
Tannins and phenolic
Steroids
Terpenoids
Jatropha seed
+
+
-
Desert date seed
+
+
+
-
Neem seed
+
+
+
+
+
Tobacco leaf
+
+
+
+
+ = Present; - = Absent.
A
B
Hilum
Sub-acute tip
Round base
Figure 1. Conidium of Cercospora arachidicola (A) and broken conidium of Cercosporidium
personatum (B) with distinct hilum at base.
Growth inhibition of fungal isolates
Disease incidence
Topsin-M treated plants produces 100% mycelia growth
inhibition (Table 2). All aqueous extract at 100 g/l
recorded the highest inhibition percentages. Desert date
seed extract (DDSE) at 100 g/l significantly (P < 0.001)
inhibited the radial growths of both fungi compared to all
levels of concentrations of plant extracts used with
inhibition percentages of 90.33 and 84.96% in C.
arachidicola and C. personatum, respectively. Even
aqueous DDSE at 75 g/l was comparable to neem seed
extract (NSE) at 100 g/l but was significantly higher (P <
0.001) than 100 g/l of jatropha seed extract (JSE) and
tobacco leaf extract (TLE). Apart from DDSE at 100 and
75 g/l, NSE 100 g/l was the next best with percentage
mycelia inhibition of 80.88 and 72.32% in both C.
arachidicola and C. personatum, respectively. Different
concentrations of tobacco leaf extract at 25, 50, 75 and
100 g/l reduced mycelial growth of both fungi. However,
TLE was not as effective compared to DDSE, NSE and
JSE in fungi-toxic activity against Cercospora leaf spot
diseases (Table 2).
In both 2014 and 2015 cropping seasons, plants treated
with desert date extract (DDSE) recorded the lowest
disease incidence with almost the same effect as TopsinM the positive control from 3 to 7 weeks after planting
(Figure 2). Tobacco leaf extract (TLE) recorded the
highest. The disease incidence for all the plant extract
treatments was generally lower in 2015 compared to
2014. For instance, by 7 WAP in 2014, Neem leaf seed
extract (NSE) treated plants had recorded about 50%
disease incidence compared to 20% disease incidence
during the same period in 2015. By 7 WAP in both
seasons, TLE treated plants and those which were
treated with neither plant extracts nor fungicide, recorded
100% disease incidence.
Disease severity index
In the field experiment, both early leaf spot (ELS) and late
leaf spot (LLS) were more severe in all treatments during
2015 cropping season (Table 3). In 2014 and 2015
Neindow et al.
Table 2. Effects of plant extracts on mycelia growth of the fungi.
Treatment
Topsin-M (1 g/L)
Topsin-M (2 g/L)
Tops-M (3 g/L)
DDSE (25 g/L)
DDSE (50 g/L)
DDSE (75 g/L)
DDSE (100 g/L)
JSE (25 g/L)
JSE (50 g/L)
JSE (75 g/L)
JSE (100 g/L)
NSE (25 g/L)
NSE (50 g/L)
NSE (75 g/L)
NSE (100 g/L)
TLE (25 g/L)
TLE (50 g/L)
TLE (75 g/L)
TLE (100 g/L)
Control (Water)
Fr (P)
LSD (0.05)
Growth inhibition (%)
C. arachidicola
C. personatum
a
a
100.00
100.00
a
a
100.00
100.00
a
a
100.00
100.00
ef
de
73.43
71.61
de
cd
77.94
75.06
cd
c
82.16
78.30
b
b
90.33
84.96
ij
i
56.88
49.92
hi
gh
60.56
59.47
fg
g
68.71
62.91
ef
ef
75.66
67.28
i
g
58.47
60.20
gh
fg
64.35
64.63
fg
def
70.15
70.65
c
cd
80.88
73.32
l
hi
49.34
54.01
kl
hi
50.57
56.46
kl
h
51.53
57.59
jkl
gh
54.50
59.38
0.00
0.00
<0.001
<0.001
6.461
6.583
Means with different letters within the same column are significantly different at 5%.
Neem seed extract (NSE), Desert dates seed extract (DDSE), Jatropha seed extract
(JSE) and Tobacco leaf extract (TLE).
Figure 2. Influence of some botanicals on disease incidence of CLS of groundnut in 2014 and 2015 cropping
seasons. Neem seed extract (NSE), Desert Date seed extract (DDSE), Jatropha seed extract (JSE), and Tobacco
leaf extract (TLE).
447
448
Afr. J. Plant Sci.
Table 3. Effects of plant extracts on disease severity on three cultivars of groundnut in 2014 and
2015 cropping seasons.
Treatment
Plant extract
DDSE
Cultivars
Mani-Pinta
Bugla
Chinese
Disease severity index (%) cropping seasons
Early leaf spot (ELS)
Late leaf spot (LLS)
2014
2015
2014
2015
ab
a
a
ab
22.00
23.08
20.42
21.42
a
a
ab
ab
21.42
22.75
21.08
21.67
ab
a
a
ab
21.75
23.5
20.00
21.75
abcd
26.5
abcd
25.08
bcde
28.5
abc
29.92
ab
28.08
bcd
32.33
abc
JSE
Mani-Pinta
Bugla
Chinese
26.08
abcd
27
abc
26.50
29.42
abcd
29.75
bcde
30.83
abc
23.42
abc
23.08
abcd
25.42
ab
26.92
ab
25.83
abc
29.17
ab
NSE
Mani-Pinta
Bugla
Chinese
24.17
ab
24.42
ab
24.00
26.00
abc
25.58
abc
27.00
cde
29.58
bcde
28.75
ef
36.08
cde
36.33
bcd
32.58
ef
40.58
abcd
TLE
Mani-Pinta
Bugla
Chinese
28.17
abcd
28.33
bcd
30.58
35.25
cde
33.83
def
38.75
Mani-Pinta
Bugla
Chinese
a
19.92
a
20.33
ab
21.83
a
22.83
a
22.33
a
24.00
a
Topsin-M (positive
control)
19.25
a
19.00
a
19.67
20.67
a
20.33
ab
21.00
de
30.50
cde
29.08
f
39.83
<0.001
7.001
de
39.17
cde
35.92
f
47.28
<0.001
7.754
de
Water (negative control)
Mani-Pinta
Bugla
Chinese
35.08
cde
33.42
e
42.58
<0.001
9.920
39.83
def
37.17
f
47.92
<0.001
10.379
Fr (P)
LSD (0.05)
cropping seasons, plants of the three cultivars (Bugla,
Chinese and Mani-Pinta) treated with DDSE recorded a
significantly lower (P < 0.001) severity similar to TopsinM, whereas those treated with TLE recorded significantly
higher (P < 0.001) severity comparable to the negative
control. A similar trend was observed for the late leaf spot
in both seasons
Yield and yield parameters
Plants treated with DDSE in both cropping seasons
recorded significantly higher (P < 0.001) pod yield while
those treated with TLE recorded the lowest (Table 4).
However, the pod yield of DDSE treated plants in 2015
(1275 kg/ha) was higher than that in 2014 (931 kg/ha).
Significant differences (P < 0.001) were observed among
the treatments in both seasons except jatropha seed
extract (JSE) and neem seed extract which yielded 931
and 1004 kg/ha, respectively but the differences were not
significant.
Generally, plants treated with DDSE in both seasons
produced heavier seeds than all the other treatments
abcd
abc
cde
a
ef
except Topsin-M the positive control (Table 4). Dry seed
yield from all treatments in 2015 were higher than those
produced in 2014. For instance, seed yield from DDSE
treated plants in 2014 and 2015 were 992 and 751 kg/ha,
respectively.
In both cropping seasons, DDSE treated plants
produced a significantly higher 100 pod weight than all
the other treatments except Topsin-M. Plants treated with
TLE recorded the least 100 pod weight in both seasons
(Table 4).
In 2014 cropping season plants treated with DDSE
produced a higher 100 seed weight that all the other
treatments but the differences were not significant at 5%.
However, in 2015 DDSE treated plants recorded 100
seed weight of 49.82 g which was comparable to that of
Topsin-M treated plants (50.72) but significantly higher (P
< 0.001) than the other treatments (Table 4).
DISCUSSION
Alkaloids, tannins and phenolic compounds were found in
all the botanicals used. This confirms the report that plant
Neindow et al.
449
Table 4. Effects of plant extracts on 100 pod weight, 100 seed weight, dry pod and seed yields in 2014 and 2015 cropping seasons.
Plant extract
Desert Date Seed Extracts
Jatropha seed extract
Neem Seed Extract
Tobacco leaf Extract
Topsin-M (positive control)
Water (negative control)
Fr (P)
LSD (0.05)
Dry pod yield
(kg/ha)
2014
2015
b
b
931.00
1275.00
c
c
729.00
931.00
b
c
875.00
1004.00
c
d
626.00
692.00
a
a
1095.00
1322.00
d
d
426.00
581.00
<0.001
<0.001
103.6
140.9
Dry seed yield
(kg/ha)
2014
2015
b
a
751.00
992.00
c
b
546.00
698.00
b
b
688.00
786.00
c
c
504.00
570.00
a
a
922.00
1045.00
d
d
306.00
430.00
<0.001
<0.001
80.3
124.9
extracts contain phytochemicals such as phloretin,
tannins, allicins, and azadirachtin which have
antimicrobial properties (Gurjar et al., 2012). Desert date
seeds, neem seeds and tobacco leaves contained
saponins. Terpenoids were detected in neem seeds and
tobacco leaves. Neem seeds also contained steroids.
Kishore et al. (2001) observed the manifestation of these
bioactive compounds in different plant materials. It has
been noted that plant extracts with antimicrobial property
can be either specific or broad spectrum in action against
pathogens (Gurjar et al., 2012).
The fungal pathogens isolated and identified from
infected groundnut leaves were C. arachidcola and C.
personatum which are the causative agents of
Cercospora leaf spot diseases of groundnut. The
conidium of C. arachidicola was sub-hyaline or pale
yellow, obclavate or cylindrical and septate with a
rounded base and sub-acute tip. McDonald et al. (1985)
observed related morphological characteristics. However,
the conidium of C. personatum was obclavate or
cylindrical, light coloured and the base was shortly
tapered with a conspicuous hilum. This morphological
description is similar to that reported by Ijaz (2011).
The in vitro studies showed significant differences (P >
0.001) among plants treated with various botanicals and
the control treatment. The results also indicated that the
efficacy of the different extracts is also dependent on the
type of plant material. Therefore, the level of inhibitions of
C. arachidicola and C. personatum were dependent on
the type of plant extract and concentration level. This
conforms to the works of Ibiam and Nwalobu (2016) who
postulated that aqueous extract of Asipilia africana and
Vernonia amygdalina decreased the vegetative growth of
Hendersonia celtifolia as concentration increases. All
extracts at 100 g/l especially desert date seed, neem
seed and jatropha seed extract significantly inhibited the
vegetative growth of the test fungi compared to tobacco
leaf extract and control (negative). Again, this confirms
the findings of Akinbode (2010) who observed that some
botanicals at 100% concentration significantly inhibited
the growth of Curvularia lunata. However, TLE was not
100 pod weight
(g)
2014
2015
ab
a
87.90
87.57
cd
c
75.40
56.39
bc
b
85.30
67.07
d
d
74.50
49.86
a
a
96.80
88.23
e
d
45.70
49.86
<0.001
<0.001
10.46
5.397
100 seed weight
(g)
2014
2015
b
a
39.50
49.82
b
c
36.70
32.86
b
b
37.50
37.31
b
d
37.20
30.19
a
a
46.70
50.72
c
d
23.60
27.67
<0.001
<0.001
5.21
3.75
as effective compared to DDSE, NSE and JSE in its
fungi-toxic activity against Cercospora leaf spot diseases.
The results showed that plant extracts lowered the
disease severity index with desert date seed extract at
100 g/l recording the least severity index percentage
which was statistically similar to Topsin-M at 2 g/l. Plants
treated with 100 g/l each of DDSE, NSE, JSE and TLE
produced heavier pods. This can be attributed to the
phytochemicals since some of them are known to induce
growth. This supports the work of Ambang et al. (2011)
that an increase in the concentration of Thevetia
peruviana seed extract reduced the rate of spread of
Cercospora leaf spot of groundnut.
Groundnut plants of all the three cultivars when sprayed
with aqueous desert date seed extract had consistently
lower disease incidence and severity in both 2014 and
2015 cropping seasons and the effect was comparable to
the positive control (Topsin-M). This was followed by
neem seed extract and then jatropha seed extract with
tobacco leaf extract being the least. Therefore, the
efficacy of the plant extracts could be attributed to the
presence of the fungitoxic phytochemicals such as
phenolic compounds, steroids and terpenoids. This
confirms that phenols and saponins extracted from higher
plants possess anti-fungal compounds against various
microbes (Halama and Haluwin, 2004). However, the
difference in efficacy of the four plant extracts could be
attributed to the differences in the nature of their active
ingredient (Ngegba et al., 2017). DDSE, NSE, JSE and
TLE significantly increased yield parameters including
100 pod weight, 100 seed weight, dry pod and seed
yields in both 2014 and 2015 cropping seasons compared
to the negative control. This could be attributed to the
antifungal properties which retarded or inhibited the
activity of the fungi leading to a decrease in disease
incidence and disease severity. This could have led to an
increase in photosynthetic activity which enhanced
vegetative growth, net assimilation and dry matter
accumulation, resulting in more yield. The findings of this
study support the report by Hossain and Hossain (2013)
that plant extracts maximize yield of groundnut
450
Afr. J. Plant Sci.
comparative to the control (negative).
Conclusion
Desert date seed, neem seed, jatropha seed and tobacco
leaf extracts suppressed the growth of C. arachidicola
and C. personatum. The studies showed that efficacy
increases as concentrations of plants extracts increases
and the level of efficacy also depends on the type of plant
material used. All concentrations at 100 g/l extracts
significantly inhibited the vegetative growth of the test
fungi. The use of desert date seed extract (DDSE), neem
seed extract (NSE) and jatropha seed extract (JSE)
consistently reduced disease incidence and severity of
both C. arachidicola and C. personatum than tobacco leaf
extract (TLE) and negative control. However, the most
effective plant extract was aqueous DDSE which was
nearly as potent as the positive control, Topsin-M in 2014
and 2015 cropping seasons followed by NSE and JSE.
Since DDSE was the most effective in both in vitro and
field studies, it is recommended for the management of
Cercospora disease of groundnut by farmers as an
alternative to expensive inorganic fungicides.
CONFLICT OF INTERESTS
The authors have not declared any conflict of interests.
REFERENCES
Akinbode OA (2010). Evaluation of antifungal efficacy of some plant
extracts on Curvularia lunata, the causal organism of maize leaf spot.
African Journal of Environmental Science and Technology 4(11):797800.
Ambang Z, Ndongo B, Essono G, Ngoh JP, Kosma P (2011). Control of
leaf spot disease caused by Cercospora sp. on groundnut (Arachis
hypogaea) using methanolic extracts of yellow oleander (Thevetia
peruviana) seed. Australian Journal of Crop Science 5(3):227-232.
Barnett HL, Hunter BB (1998). Illustrated Genera of Imperfect Fungi.
The American Phytopathological Society Press, St. Paul, MN, USA.
218p.
Begum F, Mahal F, Alam S (2010). Inhibition of spore germination and
mycelia growth of three fruit rot pathogens using some chemical
fungicides and botanicals. Journal of Life and Earth Science 5:23-27.
Chaube HS, Pundhir VS (2009). Crop diseases and their management.
New Delhi: PHI Learning Private Limited. P 703.
Chiteka ZA, Gorbet DW, Shokes FM, Kucharek TA, Knauft DA (1988).
Components of resistance to late leaf spot in peanut I. Levels of
variability- implications for selection. Peanut Science 15:25-30.
DAI and Nathan Associates (2014). Development Alternatives Inc. and
Nathan Associates London Ltd. Groundnut Market Diagnoses, DFID
Market Development (MADE) in Northern Ghana Programme. pp. 127.
Available
at:
http://africasoilhealth.cabi.org/wpcms/wpcontent/uploads/2016/10/MADE-Groundnut-Diagnostics-Ghana.pdf
Edeoga HO, Okwu DE (2005). Phytochemical constituents of Nigerian
medicinal plants. Africa Journal of Biotechnology 4(7):685-688.
Eman SHF (2011). First record of Cercospora leaf spot disease on okra
plants and its control in Egypt. Journal of Plant Pathology 10:175180.
Gurjar SM, Ali S, Akhtar M, Singh SK (2012). Efficacy of plant extracts
in plant disease management. Agricultural Science 3(3):425-433.
Halama P, Haluwin VC (2004). Antifungal activity of lichen extracts and
lichenic acids. Biocontrol 49:95-107.
Hossain HM, Hossain I (2013). Screening of different plant extracts
against leaf spot (Cercospora arachidicola and Cercosporidium
personatum) of groundnut (Arachis hypogaea L.). Bangladesh
Journal of Agricultural Research 38(3):491-503.
Ibiam OFA, Nwalobu IP (2016). In vitro inhibition of the vegetative
growth of the fungus, Hendersonia celtifolia, associated with foliar
leaf spots of Erythrina senegalensis, using the leaf extracts of
Vernonia amygdalina L and Aspilia africana L. Journal of Plant
Pathology and Microbiology 7:388.
Ijaz M (2011). Epidemiology and management of Cercospora leaf spot
of groundnut (Arachis hypogaea L.) in Punjab. Doctor of Philosophy
Thesis. Mehr Ali Shah Arid Agriculture University Rawalpindi,
Pakistan Pir. pp. 1-194.
Imoro ZA, Larbi J, Duwiejuah AB (2019). Pesticide availability and
usage by farmers in the Northern Region of Ghana. Journal of Health
and Pollution 9(23):190906.
Jordan DL, Brandenburg RL, Brown AB, Bullen GS, Roberson GT
(2012). Peanut Information. North Carolina Cooperative Extension
Service, College of Agriculture & Life Sciences, North Carolina State
University, America. pp. 100-127.
Kareru PG, Keriko JM, Gachanja AN, Kenji GM (2008). Direct detection
of triterpenoid saponins in medicinal plants. Africa Journal of
Traditional, Complementary and Alternative Medicines 5(1):56-60.
Kishore GK, Pande S, Rao NJ (2001). Control of late leaf spot of
groundnut (Arachis hypogaea) by extracts from non-host plant
species. Plant Pathology Journal 17(5):264-270.
Kobriger KM, Hagedorn DJ (1983). Determination of bean root rot
potential in vegetable production fields of Wisconsin’s Central Sands.
Plant Disease 67:177-178.
Kombiok JM, Buah SSJ, Dzomeku IK, Abdulai H (2012). Sources of pod
yield losses in groundnut in the Northern Savanna Zone of Ghana.
West African Journal of Applied Ecology 20(2):53-63.
McDonald D, Subrahmanyam P, Gibbons R, Smith DH (1985). Early
and late leaf spots of groundnuts. International Crops Research,
Institute for the Semi-Arid Tropics Patancheru, India. Information
Bulletin 21:1-16.
Mohammed KE, Agoyi EE, Odong TL, Miesho B, Okello DK, Giregon O,
Rubaihayo PR, Okori P (2019). Yield penalty associated with
stacking resistance to late leaf spot, rosette diseases and drought
stress in groundnut (Arachis hypogaea L.). International Journal
Advanced Research 7(6):178-190.
Ngegba PM, Enikuomehin OA, Afolabi CG, Akintokun AK, Egbontan AO
(2017). Efficacy of plants extracts on Cercospora leaf spot incidence
and severity of groundnut (Arachis hypogaea L.) in vivo. International
Journal of Current Research 9(12):63007-63013.
Nutsugah SK, Abudulai M, Oti-Boateng C, Brandenburg RL, Jordan DL
(2007). Management of leaf spot diseases of peanut with fungicides
and local detergents in Ghana. Plant Pathology Journal 6(3):248-253.
Sabri FZ, Belarbi M, Sabri S, Alsayadi MM (2012). Phytochemical
screening and identification of some compounds from Mallow.
Journal of National Production and Plant Resources 2(4):512-516.
SARI (2014). Savanna Agricultural Research Institute, Metrological
Data. Nyankpala, Ghana. http://www.e-agriculture.gov.gh/index.php/
2014-07-22-12-23-30/csir/savanna-agricultural-research-institute
Sowley ENK, Ofori RA, Kankam F (2017). Evaluation of neem
(Azadirachta indica) seed and Cassia alata leaf extracts as surface
protectants against seed borne fungi of maize (Zea mays L.).
Pakistan Journal of Phytopathology 29(1):1-5.
Tanzubil PA, Buah SSJ, Iddrisu A, Wih K, Anyeembey JB (2017). Guide
to Sustainable and Profitable Groundnut Production in Northern
Ghana. ICRISAT 20 p.
Tshilenge-Lukanda L, Nkongolo KKC, Kalonji-Mbuyi A, Kizungu RV
(2012). Epidemiology of the groundnut (Arachis hypogaea L.) leaf
spot disease: Genetic analysis and developmental cycles. American
Journal of Plant Sciences 3:582-588.
Wall JM, Krider MM, Krewson CF, Gentry HS (1954). Steriodal
sapogenins VII. Survey of plants for steroidal sapogenins and other
constituents. Journal of America Pharmaceutical Association 3:1-7.