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European Journal of Applied Sciences – Vol. 10, No. 3
Publication Date: June 25, 2022
DOI:10.14738/aivp.103.12456. Sobowale, A. A., Agbane, J., Bamkefa, B. A., & Aduramigba-Modupe, A, O. (2022). Fungitoxic Potentials of Ocimum Gratissimum L.
and Zingiber Officinale (L.) Roscoe Extracts Against Fungi Associated with Postharvest Rot of Carica Papaya L. European Journal of
Applied Sciences, 10(3). 659-670.
Services for Science and Education – United Kingdom
Fungitoxic Potentials of Ocimum Gratissimum L. and Zingiber
Officinale (L.) Roscoe Extracts Against Fungi Associated with
Postharvest Rot of Carica Papaya L.
Sobowale Ayodele Adegboyega
Department of Botany, University of Ibadan, Ibadan, Nigeria
Agbane John
Department of Botany, University of Ibadan, Ibadan, Nigeria
Bamkefa Bukola Ayodeji
Department of Biological Sciences, Lead City University, Ibadan, Nigeria
Aduramigba-Modupe Adefoyeke Olufunmilayo
Department of Crop Protection and Environmental Biology
University of Ibadan, Ibadan, Nigeria
ABSTRACT
The fungitoxic potentials of Ocimum gratissimum and Zingiber officinale extracts
on fungi associated with rotting Carica papaya were investigated. Rotting and
healthy pawpaw species of Carica papaya were obtained from Bodija market,
Ibadan, Nigeria. Isolation of fungi from the rotting fruit was done using standard
procedures. Pure cultures of the isolated fungi were obtained on Acidified Potato
Dextrose Agar (APDA). Leaves of O. gratissimum and rhizome of Z. officinale were
obtained from Botanical Garden, University of Ibadan, Nigeria. Crude extracts
(aqueous and methanol) of the plants were obtained using standard procedures.
The antimicrobial potentials of the extracts on the isolated fungi in vitro at
concentrations of 25%, 50%, 75% and 100% were evaluated. Their interactive
effects on the pathogens were also evaluated. Cultures with 0% methanol and water
served as controls. All experiments were done in triplicates. Incubation of all Petri
plates were done at room temperature for 7 days. Radial and diametric growth of
the fungi was measured every 24 hours using a meter rule. Data obtained were
subjected to analysis using SAS (version 9.2). Mean separation was done using
Duncan Multiple Range Test (DMRT) at p≤0.05). The isolated fungi were
Colletotrichum gloeosporioides, Lasiodiplodia theobromae, and Aspergillus flavus.
Inhibitory effects of extracts of both plants and of both solvents on the isolated
pathogens were significantly better than in control. Inhibitory effect of the
methanol extracts was better than that of aqueous extracts. Inhibitory effect of O.
gratissimum extract was also significantly better than that of Z. officinale (p≤0.05).
Inhibition at all extract concentrations was significantly better than in control.
However, inhibition at 100% and 75% was higher than that at other concentrations.
Inhibition obtained with the different treatment combinations was better than that
with individual concentrations. Generally, inhibition of Lasiodiplodia theobromae
was significantly better than that of Aspergillus flavus, which in turn was
significantly better than that of Colletotrichum gloeosporioides (p≤0.05). Ocimum
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 3, June-2022
Services for Science and Education – United Kingdom
gratissimum and Zingiber officinale could be said to possess promising fungitoxic
potentials. More work is required to ascertain their potentials in vivo.
Keywords: Carica papaya, postharvest rot, fungitoxicity, Ocimum gratissimum, Zingiber
officinale
INTRODUCTION
Pawpaw (Carica papaya) is an indigenous, multi-purpose, perennial herbaceous plant that is
cultivated mainly for its fruit. It is cultivated and consumed throughout the tropical and warmer
subtropical areas of the world. Major producers of the fruit include Mexico, Brazil Germany
including Nigeria [1]. However, the ripe fruits are known to be susceptible to attack by
microorganisms such as fungi, bacteria, nematodes and viruses including rot pathogens. Spoilt
pawpaw fruits are characterized by excess softening, mycelia growth, loss of moisture,
unpleasant odour, shrinkage and total drying up of water in the fruits [2]. Infection has been
reported to occur during growth season, harvesting, handling, transport, postharvest storage
and/or after purchasing by the consumer. [3], [4], [5], [6].
Generally, biological control of postharvest diseases including the use of botanicals has
continued to gain increasing attention [7]. Basil (Ocimum gratissimum), is famous for its local
cultivation in Africa. In Nigeria, it is commonly used as spice and its medicinal properties are
well known among the locals [8], [9]. It has been reported to exert inhibitory effect against
different fungal pathogens. Ginger (Zingiber officinale), a creeping perennial rhizome, is also
famous for its several medicinal properties. It is as well widely used around the world in foods
as a spice [10], [11], [12], [13], [14], [15]. According to FAO [16], Nigeria is reputed to be among
the largest consumers of the rhizome in the world. Extracts from the rhizome is known to show
varying antimicrobial activities. Fresh juice of the rhizome has also been reported to exert
inhibitory action against several fungal pathogens [17]. Very many plants, including basil and
ginger, as well as their parts have been reported to show antimicrobial activities because they
have some naturally occurring substances which play an effective role in plant disease
resistance [18]. Antimicrobial potentials of plant extracts against plant diseases have been
severally documented. However little has been done on the interactive effects of these extracts
on plant diseases. The experiment examined the interactive effects of crude extracts of Zingiber
officinale and Ocimum gratissimum on fungi associated with rots of C. papaya.
METHODOLOGY
Collection of samples
Diseased pawpaw was identified by physical examination using the method of Balali et al. [19].
Rotting pawpaw fruits were purchased from Bodija market, kept in sterile polythene bags and
brought to the Plant Pathology Laboratory, Department of Botany, University of Ibadan.
Zingiber officinale (rhizome) and Ocimum gratissimum (leaves) were obtained from the same
market and later verified and authenticated in the Herbarium, Department of Botany,
University of Ibadan, Nigeria.
Isolation and identification of fungi
The pawpaw samples were washed with sterile distilled water and surface-sterilized with 70%
methanol. Rotting sections from the samples were cut with sterilized scalpel and surface- sterilized with 1% sodium hypochlorite for 30 seconds and rinsed in five changes of sterile
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661
Sobowale, A. A., Agbane, J., Bamkefa, B. A., & Aduramigba-Modupe, A, O. (2022). Fungitoxic Potentials of Ocimum Gratissimum L. and Zingiber
Officinale (L.) Roscoe Extracts Against Fungi Associated with Postharvest Rot of Carica Papaya L. European Journal of Applied Sciences, 10(3). 659-
670.
URL: http://dx.doi.org/10.14738/aivp.103.12456
distilled water. They were dried with sterile paper towel and later inoculated on Petri plates of
Potato Dextrose Agar (PDA). All plates were incubated at 28oC for 7 days and observed daily for
fungal growth. The fungi were sub-cultured to obtain pure cultures which were later put on
PDA slants. Morphological characterization and identification of all isolated fungi was done
following standard procedures [20], [21], [22], [23]. Pathogenicity tests was conducted for the
isolated fungi following standard procedures.
Preparation of plant extracts
Fresh bulbs of ginger (Zingiber officinale) and fresh fully expanded leaves of African basil
(Ocimum gratissimum) were washed thoroughly under running tap water and later soaked in
1% Sodium hypochloride for 30 seconds before rinsing in 5 exchanges of sterile distilled water.
They were air dried at room temperature for two weeks and then grinded to get fine powder.
The powdered samples were added to a different conical flasks containing the extraction
solvent (sterile distil water and methanol). The mixtures were allowed to stand for 48 hours
with periodic shaking using rotary shaker in order to homogenize. Filtration was done through
a double layered muslin cloth and No. 1 Whatman filter paper prior to evaporation. The filtrate
was dried and concentrated using rotary evaporator. The dried extract was stored in sterile
bottle at -20oC for further use.
Evaluation of effect of the plant extracts on growth of the fungal isolates
The extracts were prepared at various concentrations of 25%, 50%, 75%, and 100%
represented as 0.025 g/ml, 0.05 g/ml, 0.075 g/ml and 0.01 g/ml. For each extract, 2ml of each
concentration was transferred into empty sterile Petri plate under sterile conditions, after
which 15ml of molten PDA was dispensed into each Petri plate under sterile conditions. The
plates were gently rotated to ensure even dispersion of the extracts and then allowed to gel.
Each fungus was then inoculated at the center of each Petri plate. This was done by inoculating
a 4 mm diameter mycelia disc of 7 days old culture of each of the three test fungi. Petri plates
with 0% extract served as control. All experiments were done in triplicates and incubation was
done at 28oC for 7 days. Diametric and radial growth of the growing fungi was measured at 24
hours interval for 7 days using meter rule along two perpendicular lines drawn on the reverse
of the plates. Effects of the extracts on growth of the fungi was examined using the method of
Sangoyomi [24]. The effects aqueous and methanol extracts of ginger Zingiber officinale (Zo)
and basil Ocimum gratissimum (Og), as well as their interactive effects on growth of the isolated
fungi was examined at different concentrations, viz., Zo25%+Og25%, Zo25%+ Og50%, Zo25%
+ Og75%, Zo25%+ Og100%, and Zo50% + Og25%, Zo50%+ Og50%, Zo50%+ Og75%, Zo50%+
Og100%, and Zo75%+ Og25%, ZO75%+ Og50%, Zo75%+ Og75%, Zo75%+ Og100%, and
Zo100%+ Og25%, Zo100%+ Og50%, Zo100%+ Og75%, and Zo100%+ Og100%.
Data Collection and analysis
Radial and diametric growth of the fungi were measured daily using a meter rule while growth
inhibition was measured using the formula below:
Growth inhibition (%) = [(DC- DT)/DC] X 100
Where DC = average diameter of control
DT = average diameter of fungi colony with treatment